C 3.0.0.0- Before You Begin

TypeDelta (Differential)Maximum Temperature
Annealed+80°FΔ N/A
Tempered+120°FΔN/A
Laminate- Annealed+80°FΔ 145°F
Laminate- Tempered+120°FΔ145°F
Mirrored+80°FΔ N/A

Fig. 3110A

⚠ IMPORTANT NOTE ⚠: When undertaking glass restoration, it’s crucial to account for the material’s thermal expansion – its tendency to expand and contract with fluctuations in temperature. This characteristic, if not properly managed, can lead to the risk of cracks or breakage during the scratch removal process. To ensure safety, it is advisable to maintain the temperature within a specific differential range; surpassing this range can result in thermal stress, which may lead to the glass fracturing.

To control the risk of thermal stress, one must ensure the work area is allowed to cool sufficiently. Employing an infrared (IR) thermometer to consistently monitor the temperature can prevent the heat generated by abrasive disks and felts through friction from causing excessive thermal expansion. It is critical to keep the temperature of the heated section in balance with the rest of the glass to prevent any drastic temperature differences that could compromise the glass integrity.

Fig. 3100B

Fig. 3100C

While monolithic glass panes do not have a friction-induced maximum temperature limit and the scratch removal can, in theory, be conducted in various climates, this does not always hold true for laminated panes. Laminated panes have a set maximum temperature that should not be exceeded due to their distinct composition and structural properties. While the glass itself maintains a standard temperature differential, the interlayer (PVB, SGP, EVA, etc.) has a lower melting point, and as such has the propensity to deform when subjected to heat. While the glass unit itself may appear unaffected by excessive heat, a deformed interlayer may cast a distinct shadow.

Masks & Respirators
Respiratory Hazards in Glass Restoration:
The process of restoring glass surfaces inherently results in the release of glass particulate and silicate dust. These airborne particles present a significant health hazard, particularly to the respiratory system. Prolonged or frequent inhalation of these particulates can lead to serious respiratory conditions, including silicosis—a potentially fatal lung disease—and other debilitating respiratory illnesses.

Essential Protective Gear:
To mitigate these risks, it is imperative to use appropriate respiratory protection. At a minimum, a face mask and a respiratory ventilation system with an N95 rating should be employed. However, for enhanced safety, especially in situations involving prolonged exposure or high volumes of dust, the use of a NIOSH-approved particulate respirator with a P100 rating is strongly recommended. These respirators provide a higher level of protection against the most penetrating particles, which are capable of causing severe lung damage.

Ventilation and Air Filtration:
Alongside personal protective equipment, proper ventilation and robust air filtration in the work area are crucial for controlling the concentration of airborne particulates. These measures help to reduce the overall exposure to harmful dust.

Training and Protocol Adherence:
It is essential that all operatives involved in glass restoration are thoroughly trained in the correct usage and regular maintenance of respiratory protection equipment. Strict adherence to safety protocols and guidelines is vital to ensure the health and safety of everyone involved in the restoration process.

Fig 3120A

Protective Eyewear

Potential Eye Hazards:
While the risk of eye injury in glass restoration may not be as pronounced as respiratory risks, it is nonetheless present and should be addressed with appropriate caution. The process can involve the scattering of minute glass fragments or dust, which, if they come into contact with the eyes, can cause irritation, discomfort, or even scratches to the eye surface.

Importance of Eye Protection:
As a precautionary measure, wearing protective eyewear is strongly advised during glass restoration work. Safety glasses or goggles provide a barrier against airborne particles, significantly reducing the risk of eye irritation or injury.

Selection of Protective Eyewear:
Choose safety glasses or goggles that conform to recognized safety standards. Eyewear should fit comfortably, provide a clear field of vision, and, ideally, include features such as anti-fogging and scratch-resistant lenses. For environments with higher particulate concentrations or in situations where glass shards are more prevalent, goggles that seal around the eyes offer enhanced protection.

Best Practices:
It is good practice to wear protective eyewear at all times during restoration work, even if the perceived risk is low. Regular cleaning and inspection of the eyewear for any damage or wear are also important to ensure they provide effective protection.

Fig. 3120B

Potential Risks from Rotary Polisher and Heat:
In the glass restoration process, using a rotary polisher equipped with abrasive disks can present certain risks. While direct exposure to the spinning disk is typically minimal, there is still a chance of accidental contact. Moreover, the head of the polisher can generate significant heat during the polishing process, potentially causing discomfort or minor burns over prolonged use.

Gloves as a Recommended Safety Measure:
While the use of gloves in glass restoration is optional, it is recommended for added safety and comfort. Gloves act as a protective layer, offering a degree of insulation against the heat from the polisher and minimizing the risk of abrasions from incidental contact with the spinning disk.

Selecting Suitable Gloves:
If you choose to wear gloves, opt for a pair that balances protection and functionality. The ideal gloves should be resistant to heat and mild abrasion, while still allowing for sufficient dexterity and tactile feedback necessary for precise control of the polisher and handling of glass materials.

Comfort and Heat Protection:
Gloves can also enhance comfort, especially during lengthy restoration sessions, by providing a barrier against the heat generated by the polisher. This can help maintain focus and efficiency without the distraction of heat discomfort.

Regular Inspection and Replacement:
For those opting to use gloves, regular checks for wear and damage are essential to ensure they continue to offer adequate protection. Replace gloves as necessary to maintain their protective qualities.

While gloves are not mandatory in glass restoration, their use is recommended for an added layer of protection and comfort. They serve as a simple yet effective means to safeguard against the minor risks associated with the rotary polisher and heat during the restoration process.

Fig. 3120C

The GlassRenu system utilizes three grades of silicone carbide based abrasives, called RenuDisks, to remove material from glass surfaces, allowing the resurfacing of damaged areas, restoring glass to like-new luster. RenuDisks are available in three grades of abrasivity, and four size classes.

3”5”6”8”
Redxxx
Blackxxxx
Greyxxxx

Fig. 3210A

Fig. 3210B

Also referred to as the “Pre-Polish Disk,” the Grey RenuDisk is the final abrasive disk used in the GlassRenu system. Used at three different speeds, this disk refines the work area to a fine haze, allowing us to quickly polish the glass back to full luster.

ItemPart. No. (Standard)Part. No. (Original)
3” Grey RenuDisk106-4035108-4035
5” Grey RenuDisk106-4055108-4055
6” Grey RenuDisk106-4065108-4065
8” Grey RenuDisk106-4085N/A

Fig. 3211A

Fig. 3211B

The Black RenuDisk is the first abrasive disk used in the GlassRenu system for CAT-2 and CAT-3 damage. The Black RenuDisk is a more robust abrasive, allowing the expedient removal of light and medium damage.

ItemPart. No.
3” Black RenuDisk106-4033
5” Black RenuDisk106-4053
6” Black RenuDisk106-4063
8” Black RenuDisk106-4083

Fig. 3212A

Fig. 3212B

The Red RenuDisk is the first abrasive disk used in the GlassRenu system for CAT-4 damage. The Red RenuDisk is the most robust abrasive, allowing the expedient removal of heavy damage.

ItemPart. No.
3” Red RenuDiskN / A
5” Red RenuDisk106-4051
6” Red RenuDisk106-4061
8” Red RenuDisk106-4081

Fig 3213A

Fig. 3212B

The GlassRenu Polishing Felt is used in conjunction with GlassRenu Polishing Compound in the final step of the GlassRenu System in order to restore glass to full luster.

ItemPart No.
3” Polishing Felt106-4003
5” Polishing Felt106-4005
6” Polishing Felt106-4006

Fig. 3220A

Fig. 3220B

GlassRenu Foam Finishing Pads are used in conjunction with GlassRenu Cutting Compound in the first step for removing CAT-1 damage.

ItemPart No.
5” Finishing Foam (3 Pack)106-4357
5” Finishing Foam (5 Pack)106-4557
6” Finishing Foam (3 Pack)106-4367
6” Finishing Foam (5 Pack)106-4567

Fig. 3230A

Fig. 3230B

GlassRenu Backing Pads serve as the interface between the Renudisks, Polishing Felts, and Foam Finishing Pads and the Polisher.

Backing Pads are available in SAE (⅝-11) and Metric (M14) threadings.

ItemPart No. (SAE)Part No. (Metric)
3” Backing Pad106-1113107-1113
5” Backing Pad106-1115107-1115 
6” Backing Pad106-1116107-1116 
8” Backing Pad106-1118107-1118 

Fig. 3240A

Fig. 3240B

GlassRenu Compounds are a proprietary blend of high purity rare earth minerals designed to quickly and efficiently restore and polish glass surfaces.

The Polishing Compound is used during the full GlassRenu Restoration process, where as the cutting compound can be used independently for most CAT-1 Hard Water/ Mineral Damage

ItemPart No.
Polishing Compound – 16 oz106-4001
Polishing Compound – 1lb106-4011
Cutting Compound –  16 oz106-3001
Cutting Compound – 1lb106-3011

Fig. 3250A

Fig. 3250B

Fig. 3250C

Fig. 3260A

Polisher Minimum Requirements
Power SourceCorded
Drive ActionDirect Rotary
RPM Range600- 3000
Arbor⅝-11 (SAE) / M14 (Metric)
Common Brands/ Model Number
Makita9227C/ 9237C
DewaltDWP849X
Milwaukee5540
Bauer56792

Fig. 3260B

On/Off Trigger:
The On/Off Trigger is the primary control for the polisher’s power. Pressing this button activates the polisher’s spindle rotary drive action. This feature allows for easy start and stop of the polishing process, ensuring precision and control during operation.

Trigger Lock:
The Trigger Lock is a safety feature that locks the power trigger in its active state. Engaging the trigger lock during operation allows the operator to adjust their grip and move their hand without causing unintended pressure changes or operational interruptions. This feature helps maintain consistent operation and reduces hand fatigue.

RPM Adjustment:
With the RPM Adjustment knob, operators can finely tune the operational speed of the polisher. This control allows for precise adjustments to the rotational speed, accommodating different stages of the restoration process and different types of damage on the glass.

RPM Guide:
An RPM Guide, typically located directly on the polisher, provides a reference for the operational speed. In cases where the guide is not present on the tool, users should refer to the owner’s manual for detailed information on speed settings and recommendations.

Spindle:
The Spindle is the threaded component that protrudes from the head of the polisher and rotates during operation. GlassRenu Backing Pads are designed to be threaded directly onto this spindle, ensuring a secure and stable attachment for effective restoration work.

Spindle Lock:
The Spindle Lock is a mechanism used to secure the spindle in place when the polisher is not in use. This feature is particularly useful for changing or removing the backing pad safely and efficiently, without the risk of the spindle turning.

In glass restoration, the infrared (IR) temperature gun is an essential tool, crucial for ensuring the safety and effectiveness of the restoration process. This non-contact device enables technicians to accurately monitor the surface temperature of the glass, providing vital real-time feedback crucial for maintaining optimal working conditions.

Monitoring for Safety and Efficiency:
Different glass types respond uniquely to temperature variations, particularly when damaged. The IR temperature gun plays a pivotal role in ensuring that the glass is kept within safe temperature ranges during the restoration process. Understanding and managing these temperature differentials are essential to minimize the risk of thermal stress or damage, especially important when working with various types of glass such as annealed, tempered, or laminated.

Understanding Temperature Implications:
The use of the IR temperature gun, while straightforward, requires an understanding of how temperature variations impact different types of glass. Technicians must be adept at interpreting the temperature data and understanding its implications on their restoration strategy. This understanding is critical for adjusting techniques in real time, particularly when employing heat-generating tools, to prevent excessive heating and ensure the structural integrity of the glass.

The integration of an IR temperature gun in glass restoration showcases a commitment to precision and careful handling. It highlights the importance of adapting restoration techniques to the thermal characteristics of each type of glass, ensuring high-quality restoration outcomes and the preservation of the glass’s integrity.

Fig. 3270A

In the toolkit of glass restoration, the metal rasp file is an indispensable tool, specifically designed to enhance the longevity and efficiency of other essential tools. Featuring a dual-sided design with both a flat and a slightly rounded side, each having mild and aggressive halves, this rasp file is aptly suited for a range of tool maintenance tasks.

Maintaining Abrasives:
The file’s flat, less aggressive side is ideal for removing glass stock or dust from abrasive surfaces. This gentle tapping technique re-exposes the abrasive material, crucial for maintaining the effectiveness of these tools over extended periods.

Caring for Polishing Felts:
Conversely, the more aggressive, rounded side of the file is adept at two key maintenance tasks for polishing felts. It effectively removes caked-on polishing compounds and is instrumental in raising the natural fibers of the felts, ensuring they continue to provide a consistent and high-quality polish.

Fig. 3280A

The true value of the metal rasp file in glass restoration lies in its utility beyond direct restoration work. It plays a pivotal role in the upkeep and optimization of other tools, directly impacting the quality and efficiency of the restoration process. Its use is a prime example of how proper tool maintenance is integral to achieving excellent glass restoration results, highlighting the interdependence of tools in this meticulous craft.

In the process of glass restoration, the use of cleaning agents, while seemingly straightforward, is an essential step in both preparing for and finalizing the restoration work. Any standard glass cleaning agent that is safe for use on glass surfaces can be effectively employed in this context. The primary function of these cleaning agents is to ensure that the glass is free from surface contaminants before the commencement of the restoration and to remove any residual compounds after the polishing phase.

Agents such as a diluted solution of Dawn dish soap and water, pure water systems, or commercial glass cleaners like Windex and Spray Away are all suitable for these purposes. Prior to the abrasive and polishing stages, a thorough cleaning helps in providing a clear and uncontaminated surface, which is crucial for the effectiveness of the abrasion process. This initial cleaning step helps in revealing the true extent of the damage and ensures that the abrasives and polishing compounds work directly on the glass without interference from surface debris.

Post-restoration, these cleaning agents play a vital role in removing any excess polishing compound, ensuring that the restored glass is not only structurally sound but also visually pristine. The objective is to leave the glass surface spotless and streak-free, showcasing the results of the meticulous restoration process.

Fig. 3290A

  • Verify that the threading of the GlassRenu backing pads matches that of your polisher. GlassRenu backing pads come in both SAE and Metric threadings, and it’s crucial that these are compatible to ensure a secure and effective fit.
  • Attach the backing pads directly to the spindle of the polisher. This step is important for ensuring that the backing pad is securely fastened and aligned correctly for optimal performance during restoration.
  • Secure RenuDisks to the black ‘hook’ surface of the backing pad. Proper attachment of these disks is key to achieving uniform abrasion and polishing results.
  • When storing the polisher, remove the backing pads. This practice helps to prolong the life of both the backing pad and the polisher spindle.
  • Store the backing pads in a way that avoids prolonged pressure on them. Excessive pressure can compress and deform the soft interface of the pad, potentially causing imbalance and uneven wear when the tool is next operated.

Fig. 3400A

  • Each RenuDisk has two distinct sides: a rough ‘abrasive’ side for the restoration work, and a soft ‘loop’ side for attachment to the backing pad.
  • Secure the RenuDisk to the backing pad by aligning the loop side of the disk with the pad’s hook surface. It’s important to use a RenuDisk that matches the size class of the backing pad and to center the disk accurately for balanced operation.
  • As you use the RenuDisk, glass stock will accumulate on its surface. To maintain optimal performance, periodically unclog the disk:
  • Ensure the polisher is switched off and the disk is stationary.
  • Use the flat, non-aggressive side of a rasp file or a wire brush for cleaning.
  • Apply gentle tapping motions on the RenuDisk surface to dislodge the accumulated glass stock. Avoid brushing as it can damage the disk.
  • If the abrasive surface of black or red RenuDisks remains intact after use, they can be cleaned, carefully removed, and stored for future restoration projects.
  • Store RenuDisks in a way that maintains their integrity. Avoid bending, folding, or applying pressure, as these actions can damage the disk and affect its performance in future uses.

Fig. 3420A

Fig. 3420B

Fig. 3420C

Fig. 3420D

  • Polishing Felts have two sides; an off-white wool felt side, and a black felt “loop” side.
  • Polishing felts are secured to the backing pads’s hook surface via the loop side of the felt.
  • Always use the same size class Polishing Felt as the backing pad.
  • Align the Polishing Felt directly in the center of the backing pad.
  • Before every use of the Polishing Felt, lightly abrade the surface of the felt side (Fig. 3430A) of the backing pad, removing leftover compound and simultaneously gently raising the natural fibers.
  • Polishing Compound is applied directly to the Polishing Felt.
  • Polishing Felts will last well over 200+ Sq Ft. when taken care of properly
  • Store in a clean, dry environment to avoid any potential surface contaminants.

Fig. 3430A

Fig. 3420B

Bottle:
Fill the 16oz (475ml) bottle to the top with clean water. Shake well to evenly disperse the compound before every use.

1lbs Jar: 
Add 45g (one scoop if compacted, two scoops if loose) of polishing compound to a 16oz (475ml) bottle. Fill the bottle to the top with clean water. Shake well to evenly disperse the compound before every use.

Polishing Compound is applied directly to the Polishing Felt. Apply 3-4 squirts (approx. ¼-½ oz.) around the circumference of the Polishing Felt.

Fig. 3440A

Fig. 3440B

This section focuses on the environment or workspace recommendations and considerations for field repairs (Repairs done on glass panes that have been installed, glazed, framed, etc.) and repairs done in house, on glass that has yet to be installed.

Field repairs in glass restoration present unique challenges and requirements compared to in-house repairs. Understanding these differences is key to executing successful repairs in various field settings. Here are some critical considerations and best practices for field glass restoration:

  • Orientation and Location of Glass Panes: Field repairs are predominantly performed on glass panes in a vertical orientation, already installed within the building envelope, or as partitions in offices and other spaces. These panes often extend beyond the ideal ‘Strike Zone’ as defined in Section C 3.8.3.0 – Body Positioning and Strike Zone. To accommodate this, technicians may need to use workbenches, ladders, scaffolding, or powered lifts to access and effectively restore the entire area of the glass.
  • Considerations for Framing and Glazing: In field settings, special attention must be given to the framing or glazing of the window. These elements can impact the repair area and necessitate extra precautions to protect the existing facade. It’s recommended to use masking tools such as painters tape, paper, drop cloths, and tarps. Additionally, having receptacles for collecting glass stock and disposing of used disks is essential to maintain cleanliness and safety.
  • Power Requirements for Equipment: Field repairs require careful planning regarding power supply for polishers and other equipment. In some cases, it may be necessary to use separate fuses, breakers, or generators, especially if the available power sources are limited or if there are concerns about overloading existing circuits.
  • Temperature Considerations in Restoration: Temperature plays a crucial role in field glass restoration, especially when working with laminated glass. To avoid deformation of the interlayer(s), it is important to keep the maximum temperature below 145 degrees Fahrenheit, as detailed in Section C 3.1.1.0 – Thermal Expansion. High temperatures can also cause the water in the polishing compound to evaporate quickly, reducing the effectiveness and ease of the polishing process. Depending on the ambient temperature, it may be beneficial or necessary to use cooling techniques. Tools like shade cloths, tents, or tarps can be used to block direct sunlight, while fans can provide consistent airflow over the work area to help maintain a steady temperature.

In conclusion, field repairs in glass restoration require a nuanced approach, considering the unique aspects of each job site. By addressing orientation and location challenges, being mindful of framing and glazing, ensuring adequate power supply, and managing temperature effectively, technicians can ensure high-quality restoration results even in the most challenging field conditions.

Fig. 3412A

Fig. 3412B

In-house or in-facility glass restoration presents a different set of conditions compared to field repairs, primarily due to fewer environmental factors to contend with. These settings offer greater flexibility and control over the repair process, particularly in terms of the orientation and positioning of the glass panes. Here are some essential factors to consider for successful in-house glass restoration:

Optimal Setup for Horizontal Repairs:

  • When performing repairs horizontally, it’s advantageous to use a work table at about waist height. This height allows for increased ease of use and better control over the polisher, facilitating a more comfortable and effective restoration process. For optimum results, it’s also recommended to elevate the glass pane slightly above the work table, especially if the table surface is solid. This elevation enhances airflow around the glass, promoting quicker heat dissipation and helping to maintain a safe working temperature.
  • Using a non-slip material under the glass pane is crucial to prevent any unintentional movement caused by the polisher’s torque. This stability is key to ensuring precise and consistent restoration work without the risk of the glass shifting or sliding during the process.

Maintaining a Clean and Organized Workspace:

  • Just as in field repairs, maintaining a clean and organized workspace is vital in-house. Utilize receptacles for collecting glass stock and disposing of used RenuDisks. Keeping the restoration area tidy not only makes the process more efficient but also minimizes the risk of glass stock becoming airborne and posing a safety hazard.

Managing Heat Generation:

  • Monitoring and managing the heat generated on the glass pane is as important in-house as it is in the field. Refer to Section C 3.1.1.0 – Thermal Expansion for guidelines on safe operating temperatures. Employ fans or other cooling tools to ensure that the temperature of the glass remains within safe limits. This consideration is particularly crucial when working with laminate glass or in conditions where the temperature might rise significantly during the restoration process.

In-house glass restoration offers certain advantages in terms of control and flexibility but still requires careful attention to setup, stabilization, cleanliness, and temperature management. By adhering to these best practices, technicians can ensure that in-house repairs are conducted safely, efficiently, and to the highest quality standards.


Mechanical Damage Assessment Matrix
Damage TypeCategorySpecification Sheet
Suction Cup MarksCAT- 1C 5.1.0.0
Fines And TicksCAT-2C 5.6.0.0
Cleaning AbrasiveCAT-2C 5.7.0.0
Metallic RubCAT-2C 5.8.0.0
Glass On GlassCAT-2C 5.9.0.0
Razor BladeCAT-3C 5.10.0.0
Masonry/ RockCAT-3C 5.11.0.0
Graffiti Scratch- LightCAT-3C 5.14.0.0
Severe ScratchesCAT-4C 5.16.0.0
Graffiti Scratch- HeavyCAT-4C 5.17.0.0
Metal Grinding DebrisCAT-4C 5.18.0.0
Media Blast DamageCAT-4C 5.19.0.0
Welding SlagCAT-4C 5.20.0.0
Large ChipCAT-4C 5.21.0.0

Fig. 3600A

Chemical Damage Assessment Matrix
Damage TypeCategorySpecification Sheet
Heat HazeCAT-1C 5.2.0.0
Mineral DepositsCAT-1C 5.3.0.0
Mineral StainingCAT-1C 5.6.0.0
Mineral EtchingCAT-2C 5.9.0.0
Light AcidCAT-3C 5.12.0.0
Medium AcidCAT-3C 5.13.0.0
Heavy AcidCAT-3C 5.15.0.0

Fig. 3600B

The initial phase of any glass restoration effort hinges on a meticulous damage assessment. This critical evaluation is methodically performed to discern the integrity and aesthetics of the glass surface, categorizing the damage detected into one of two principal types: mechanical or chemical. Mechanical damage is typically inflicted through physical means such as contact with objects, while chemical damage is caused by corrosive interactions with environmental substances. Additionally, it is imperative that the damage assessment accurately determines which surface the damage is on, and if there are other potential physical characteristics that need to be addressed. A good example of this would be determining if the damaged surface has a surface treatment or “coating” present.

To determine the surface that is damaged, inspection with variable light sources will offer a clear indication of the location of the damage. It is important, especially with Insulated Glass Units (IGU’s), to ensure that the damage is on an exterior surface and therefore accessible and repairable. If the damage is between the two panes of glass that comprise the IGU, the damage will not be repairable.

To determine if the surface that is damaged has a coating present, a simple field refraction test, commonly known as “an eraser test,” is a quick and simple method to ensure that the damage restoration will not affect or remove any surface coatings that may be present. To perform this test, place a cylindrical object on the surface of the glass and view the reflection from a 20-30 degree angle. If the bottom surface of the object is visible as an offset reflection, there is no coating on the test surface. If the bottom of the cylinder is not visible, nor is there a “ghost reflection” that is offset by the approximate thickness of the glass pane, there is a coating present on the damaged surface. Restoration of the damage will consequently remove the coating as well. This can affect the performance of the window system and/or the appearance of the glass post-restoration and should be noted and discussed with the client prior to beginning the restoration process.

Prior to inspecting the actual damage, it is crucial that restoration technicians inspect the quality of the window system, looking at overall structural integrity. If the glass is not firmly glazed (i.e., it moves in the frame) or the glass has any structural failures (large chips or cracks present), these defects should be noted, and extreme caution should be taken during the restoration process. In general, if the glass is not firmly glazed or structural failures are detected, it is recommended that the glass be either replaced or the glazing repaired prior to restoration activity.

Once a clear picture of the aforementioned variables is in hand, it is then time to assess the actual damage that is going to be restored.

To facilitate a structured analysis, damage is further delineated into four categories based on severity:

This includes the most minor imperfections which are often challenging to detect and generally do not significantly affect the glass’s structural integrity or clarity. Can be seen but not felt. This category includes deposits, staining, and minor imperfections on the surface of the glass ranging from mineral deposits to metallic rub. The category one glass restoration process does not require the use of abrasive disks for damage removal and is the least invasive process possible. While the category one methodology is designed primarily for damage that hasn’t penetrated the surface of the glass, it can be effective at removing incredibly minor scratches (primarily things that can barely be seen and not felt at all).

Visible flaws that can typically be felt with a fingernail but are shallow enough to not necessitate extensive repairs. Can be seen and felt with clean damage edges. This category includes damage such as hard water or mineral etching through light glass-on-glass damage (hook damage). The Category two restoration process requires the use of an Original Grey RenuDisk or a Black RenuDisk to abrade the surface of the glass, a Grey Renudisk to refine the abrasion, and a final polish. CAT-2 mechanical damage can generally be described as light scratches that are visible on the pane, are clean lines devoid of any chipping, and may be able to be felt with a fingernail. CAT-2 chemical damage generally involves extreme hard water or mineral damage or very light acid damage.

Defects are prominent and may impede the transparency of the glass or its structural integrity, requiring more involved restoration techniques. Can be felt and begin to exhibit minor chipping along the edges of the damage. This category includes damage stemming from improper razor blade/scraper use to intentional acid etching (graffiti). The category three restoration process requires the use of a Black RenuDisk, a Grey RenuDisk, and a final polish. Category three mechanical damage can be described visually as prominent scratches on the pane that may exhibit distinct refractions and may have very light chipping along the edge. Mechanical CAT-3 damage can be easily felt with a fingernail but not deep enough to fully catch the tip of the nail. Category three chemical damage generally results from chemical misuse and/or vandalism that has etched the surface of the glass. CAT-3 acid damage has a distinct milky white appearance, and the surface may appear lightly modeled.

The most severe level of damage, often deep and extensive, posing a risk to both the appearance and the structural stability of the glass, which may necessitate advanced restoration solutions or even replacement. Can be seen and felt, and exhibiting significant chipping. This category includes damage such as welding slag, metallic overspray, carbide scribe/diamond tooling, media blast, etc. Category four damage encompasses many types of extreme damage, almost exclusively mechanical in nature. As a scratch, category four can be described as visually exhibiting more pronounced chipping along the edge with more pronounced refraction. This type of damage is very easily felt, and it is likely easy to catch a fingernail. As welding slag and metallic overspray, it may appear spotted, discolored, bits of metal lodged inside the pane, small pin-sized holes, etc. Because of the open-ended nature of category four, strict definitions don’t quite exist.

Hard Water, or mineral damage on glass is when foreign minerality is deposited on the surface of a glass pane. This type of damage commonly begins as dissolved solids in water (irrigation), dissolved solids that leach into water (building run-off), and dissolved solids in the atmosphere (precipitation, sea air, etc.). Hard water/mineral damage can be thought of in three stages: Deposits, Staining, and Etching.

Deposits
Hard Water Deposits represent the very beginning of hard water damage. Deposits are minerality that has been left on the pane usually through the evaporation of water, leaving a distinct outline of the droplet(s) on the pane. In the early stages, deposits can easily be removed using traditional methods and solvents. Deposits can be described as existing solely on the surface of the glass, with minor adherence. Deposits are typically salts that have formed on the surface of the glass between alkaline and alkaline earth minerals bonding with halogens found in either the dissolved solids or within the glass itself. Salts are built upon ionic bonds that often can be dissociated by solvents and cleaned away. Deposits represent the only “Hard Water Damage” that can be effectively removed by chemical intervention; mechanical polishing is also extremely effective without the need to test chemistry.

Stains
Hard Water Staining occurs when deposits have been left on the pane long enough for the minerality of the deposit and the minerality of the glass to begin forming bonds. Fluctuating temperature, changing UV exposure, and time will all contribute to the bonding of these materials. Most staining cannot be removed with traditional methods and requires the use of mechanical polishing to remove. Visually, staining can appear as faint discoloration where deposits were or resembling the deposits themselves depending on the severity. Hard water stains present as “shadows” or discoloration that is left on the surface of the glass post-deposit removal. This damage will persist after solvents have been used to dissociate the salts and cleaning has been done. These stains are created by stronger and more persistent covalent bonds between trace elements in the glass and dissolved elements present in affecting water. Because staining penetrates the surface of the glass, intermingling with material deeper than the surface, mechanical polishing or abrading is the only effective method for restoration.

Etching
Hard Water/mineral etching occurs when minerality has bonded deeply into the surface of the glass, removing actual silicate material in the process. Hard water etching can be difficult to accurately determine before deposits and staining have been removed. When deposits and staining have been removed, etching presents as a faint “ghost-like” outline of where the deposit/staining was. Sans additional damage, the glass should present as perfectly clear, with a textured appearance where the surface has been eroded. Etching occurs on a longer exposure timeline between the glass and the staining agents and will often be found beneath heavy deposit “crusting.” As the outer layers of glass are exposed to the staining elements, the glass will begin to shed bits of material, leaving behind a textured surface resembling an “orange peel” appearance and feel. Once the stains have entered the etching phase, mechanical polishing and abrasion are the only viable options for restoration. Because etching has penetrated the surface of the glass, it is classified as CAT-2 damage and requires the use of abrasive disks to resurface the affected area.

Acid damage occurs when harsh chemicals or acidic substances come into contact with the glass, causing etching or severe staining. This type of damage can result from improper chemical use, such as using the wrong cleaning agents, or from intentional vandalism like graffiti. The severity of acid damage varies depending on the type of acid used, the amount of acid applied, and its dwell time on the glass. Heavier acid damage tends to exhibit mild surface modeling, while lighter acids may not leave any noticeable modeling. Despite appearing more extensive than scratch damage, the restoration process for acid etch damage is the same as for other types of damage. Mechanical polishing and abrasion are used to remove the damaged layer and restore the glass to its original clarity and smoothness.

Edges and corners present unique challenges in glass restoration. While it is possible to work all the way to the edge with frameless or unframed panes, frames and seals need to be considered once installed. Round disks and rotary tools prevent working all the way into corners of framed panes. Planning the repair area and ensuring enough room for mandatory expansions during the pre-polish step is crucial. For damage that extends to the frame or seal, allow a minimum of 2 inches surrounding the edge of the pane to ensure thorough restoration.

Throughout the damage assessment process, it is important to understand that not all damage is equal, and there will be situations where restoration no longer makes sense. While these situations are few and far between, it is imperative that as a restoration technician, you identify those times when the best course of action is to replace the glass rather than perform restoration.

Key “no-go” factors include but are not limited to:

  • Structural Failure: If the glass has any cracks, chips, or holes. This type of damage can create micro fissures and cracks in the body of the glass that can lead to catastrophic failure during the restoration process.
  • Extremely Deep Damage: If the damage appears to penetrate beyond 30% of the thickness of the glass, this damage will create an extremely unstable work piece and can lead to structural failure during the repair process.
  • Wired Security Glass: This is glass that has a wire mesh or “chicken wire” embedded within the body of the glass. This wire mesh can act as a heat sink, pulling heat throughout the glass in an unpredictable way that often leads to cracking and/or breaking during the repair process.
  • Technician Confidence: From time to time, aspects of different restoration jobs will cause the restoration technician to be wary. If there is an aspect of the project that causes the technician to be timid or wary of performing the restoration, it is likely a good indication that the project either falls beyond their skill level or presents an aspect beyond their ability. Trust your gut.

Beyond these few limitations, the restoration methods and procedures presented within this guide are more than sufficient to deliver repeatable, reliable, and high-quality repairs. Should a situation arise where you are not sure, this is a good time to reach out to the tool manufacturer for guidance.

Initial Assessment and Planning: 
Prior to initiating any glass repair process, a crucial preliminary step involves assessing and delineating the approximate area of work. This initial planning is not just about identifying the damage but also about strategically considering the need for expansion, especially around edges and corners. This foresight is essential in setting the stage for an effective and efficient repair process.

Addressing Different Categories of Damage: 
In the field of glass restoration, damage is often categorized, with CAT-1 and CAT-2 representing cases where minimal material removal is required. However, for more severe damages like CAT-3 and CAT-4, a key aspect of the GlassRenu Process involves an expansion of the work area right from the first step. This expansion is not merely about removing material from the pane but is a deliberate strategy to prevent optical distortion. By carefully and progressively enlarging the work area during the abrasion process, it becomes possible to maintain the optical clarity of the glass, ensuring that the pane remains free from any distortions that could impair its transparency or appearance.

Considering Physical Constraints: 
An additional consideration in this process is the distinction between frameless and framed glass. With frameless glass, the technician has the liberty to work across the entire surface, from edge to edge. However, framed windows introduce a physical limitation that must be accounted for. When planning the repair area for framed windows, it is imperative to acknowledge these boundaries and allocate sufficient space not just for the initial steps but also for the potential expansion of the work area. This careful planning is crucial to effectively mitigate distortion and achieve a seamless repair.

Practical Implications: 
Understanding and implementing the concept of work area expansion is a cornerstone of effective glass grinding and restoration, particularly for more severe types of damage. This approach not only ensures the structural and aesthetic integrity of the glass but also enhances the overall quality of the repair. By integrating these considerations into the repair process, technicians can achieve results that are both functionally sound and visually impeccable, upholding the highest standards of glass restoration.

When dealing with Category One damage on glass surfaces, the focus is on precise and localized restoration. This category predominantly encompasses issues like hard-water/mineral deposits and staining, which, while potentially covering the entire pane from edge to edge, do not typically penetrate deeply into the glass structure. As such, the containment of the work area can be efficiently limited to the specific regions where the damage is evident.

The nature of Category One damage allows for a straightforward restoration process, primarily utilizing foams, felts, and specialized compounds. These methods are surface-oriented and do not necessitate aggressive abrasion or deep structural intervention. Consequently, there are no extensive requirements for expanding the work area beyond the immediate vicinity of the damage. This approach ensures that the restoration process is both effective and efficient, targeting the damage directly without impacting the surrounding areas of the glass pane.

Category Two damage on glass surfaces necessitates a more involved restoration approach, specifically the use of abrasive disks. This type of damage typically extends beyond superficial surface blemishes, requiring a methodical removal process. Given the nature of the abrasives involved, it is essential to thoroughly consider both the extent and the location of the damage on the pane when planning the restoration work.

The utilization of abrasive disks implies a need for a broader work area compared to Category One damage. This expanded area accounts for the potential spread of abrasives and the controlled, even application required to effectively remove the damage without causing additional harm to the glass. Additionally, the position of the damage on the pane plays a crucial role in determining the approach and safety precautions necessary during the restoration process. Careful planning and execution are key to ensuring that the restoration is conducted efficiently, minimizing the risk of collateral damage to the glass or surrounding areas.

Category Three damage on glass surfaces demands a more intensive restoration approach, despite using the same RenuDisk as in the Category Two process. The distinguishing factor for Category Three damage lies in the depth of the imperfections, which requires significantly more extensive surface abrasion to effectively reach and remedy the bottom of the damage.

Given the depth and severity of the damage, it is crucial to strategically expand the work area in a slow and systematic manner during the abrasion process. This gradual expansion is essential to ensure thorough coverage and uniform treatment across the damaged area. By methodically increasing the scope of the work area, technicians can maintain control over the restoration process, ensuring that each layer of damage is addressed with precision and consistency. This approach not only aids in achieving optimal restoration results but also helps in minimizing the risk of unintentional damage to adjacent areas of the glass pane.

Category Four damage represents the most severe level of impairment on glass surfaces, necessitating the most comprehensive and extensive abrasion approach for effective restoration. The key challenge in addressing Category Four damage lies not only in the depth and severity of the damage but also in minimizing the resultant optical distortion that can occur with such intensive restoration processes.

To successfully restore glass affected by Category Four damage, it is imperative to progressively expand the work area. This expansion is crucial in ensuring a gradual and balanced abrasion, which is essential for reducing the likelihood of noticeable distortion in the glass. The process demands a meticulous balance between reaching the full depth of the damage and maintaining the uniformity of the glass surface.

Given the intricate nature of this restoration work, a strategic and carefully controlled approach is paramount. This involves a thoughtful progression of abrasion intensity and scope, aimed at restoring the glass’s clarity and integrity while preserving its optical properties to the greatest extent possible.

In the field of glass restoration, addressing edges and corners requires special consideration, especially when dealing with framed windows. This subsection expands on the “Determining Your Work Area” topic, focusing on the unique challenges presented by edges and corners and how to effectively plan for them.

  • Challenges with Edges and Corners: Unlike frameless or unframed panes where working up to the edge is relatively straightforward, framed windows introduce physical boundaries that must be taken into account. The presence of frames and seals creates constraints that can impact the restoration process. Additionally, the nature of round disks and rotary tools used in the GlassRenu process inherently limits the ability to reach into the very corners of framed panes, as fitting a round tool into a square corner remains a geometrical challenge.
  • Planning for Work Area Expansion: The GlassRenu process typically requires at least two separate expansions of the initial work area for CAT-2 damage, with potentially more expansions needed for CAT-3 and CAT-4 damage. Effective planning of the repair area is crucial, particularly when the damage is close to the frame or seal. It’s important to anticipate the space needed for these expansions to ensure the process is thorough and effective.
  • Recommendations for Framed Panes: When dealing with damage near frames or seals, a strategic approach is necessary. It is advisable to allow a minimum clearance of 2 inches around the entire edge of the pane. This clearance ensures there is adequate room for the mandatory expansions during the pre-polish step. Properly accounting for this space prevents any compromise in the quality of the restoration, particularly in maintaining an even and consistent finish up to the edges.
  • Consideration for Seals and Frames: In planning the work area, special attention should be given to protect seals and frames. Employing masking tools such as painters tape can safeguard these areas from accidental abrasion or damage during the restoration process.

By anticipating and effectively planning for the challenges posed by edges and corners in framed windows, technicians can ensure a comprehensive and high-quality restoration process. This careful approach ensures that the entire pane, including areas near frames and seals, is uniformly restored, maintaining the aesthetic and structural integrity of the glass.

In the field of glass restoration, maintaining the correct technique throughout the entire process is critical. The concept of “Staying Flat” – keeping the abrasive surface of the disk completely parallel to the glass pane – is central to this technique. Proper adherence to this practice ensures consistent abrasion and pre-polish, thereby preventing additional damage to the glass and avoiding optical distortion due to unintended lensing. Here are some advisements and tips to help maintain the “Staying Flat” principle during operation:

  • Pressure Application: Apply pressure directly behind the spindle of the polisher. This helps ensure even distribution of force across the RenuDisk, helping to maintain its flat alignment with the glass surface. Uniform pressure is key to consistent abrasion and pre-polish, minimizing the risk of creating uneven surfaces on the glass.
  • Sensory Feedback from the Disk: Pay attention to the physical feedback you receive from the polisher. If the disk comes on edge, you will likely feel the polisher pulling in one direction or another. This sensation is a clear indicator that the disk is no longer parallel to the glass and needs to be adjusted. Sensory feedback is a valuable tool in maintaining the correct posture and pressure during the restoration process.
  • Observing Glass Dust and Disk Trail: Monitor the glass dust generated during abrasion and the trail or path left by the RenuDisk on the pane. If you notice glass dust flying off in a particular direction or if the trail left by the disk is not the full width of the disk, these are signs that the disk is not perfectly flat against the glass. The trail should reflect the entire width of the disk, indicating a flat and uniform contact with the glass surface.
  • Training and Practice: Developing the skill to ‘Stay Flat’ efficiently takes practice. Engage in regular training sessions, focusing specifically on mastering these techniques. Over time, maintaining the correct posture and pressure will become more intuitive.

By incorporating these tips into your glass restoration practice, you can significantly improve the quality of your abrasion technique. “Staying Flat” is not just a technique but a cornerstone of professional glass restoration, ensuring the integrity of the glass and the quality of the restoration work.

Fig. 3810A

Fig. 3810B

In the GlassRenu process, the way pressure is applied plays a crucial role in determining the quality of the repair. Achieving a high-quality result hinges on the ability to apply pressure both evenly and consistently throughout the process. This careful management of pressure not only controls the amount of material being removed from the glass pane more predictably but also enhances control over the RenuDisk and polisher.

Handling the Polisher:
The design of the polisher often includes a handle (either side or loop handle) for operation. However, using these handles is not recommended for the GlassRenu process. The reason lies in the fact that the handles’ mounting holes are typically offset from the polisher’s spindle. This offset can create an imbalance, requiring additional compensation towards the rear of the polisher and complicating the pressure balance. A more effective technique is to remove the handle and grip the head of the polisher directly behind the spindle. This grip allows for pressure that is centered and aligned with the backing pad and RenuDisk, leading to a more balanced and controlled abrasion.

Using the Trigger Lock and Managing the Trigger Hand:
Engaging the trigger lock during operation is a key technique. It eliminates the need to firmly grip the polisher’s handle, which can inadvertently apply downward pressure at the rear of the machine and cause imbalance. Once the trigger is locked, the hand that would normally control the power can instead lightly adjust to correct any pressure imbalances. Furthermore, locking the trigger provides greater freedom to move the polisher around the glass surface during abrasion. This mobility is invaluable, as it allows for continuous checking of the haze quality and ensuring that the abrasion pattern is consistent and effective.

By adhering to these techniques for pressure application and polisher handling, the GlassRenu process becomes more manageable, precise, and effective. These methods not only improve the quality of the glass restoration but also make the process more ergonomic and user-friendly for the technician.

In the GlassRenu restoration process, the feedback you receive from the RenuDisk or polishing felt is a critical aspect of achieving optimal results. This feedback, particularly the physical sensation during active abrasion, pre-polishing, and polishing, provides essential insights into the effectiveness of your technique.

The Importance of Disk Feedback:
The RenuDisk or polishing felt communicates vital information about your technique and the glass surface. Understanding and interpreting this feedback is key to maintaining the correct approach throughout the restoration process.

Visualization:
It’s helpful to visualize the rotational action of the RenuDisk or felt while in operation. When the surface of the disk is completely parallel to the glass pane and pressure is evenly distributed, all forces are in equilibrium. This balanced state results in a steady, stable sensation, indicating that the disk is properly aligned.

Sensation of Balance and Movement:
With the disk parallel and forces evenly distributed, the polisher should feel balanced and generally stationary on the glass. You should be able to move the RenuDisk across the pane with minimal resistance, indicating a smooth and effective abrasion or polishing action.

Recognizing and Adjusting for Misalignment:
If the disk is not parallel to the glass during operation, you may notice a distinct “pull” in the direction opposite to the disk’s rotation. This sensation is a clear indicator that an adjustment is needed. By learning to recognize this pull, you can promptly adjust the polisher’s angle or your pressure distribution to realign the disk parallel to the glass surface.

Practice and Sensitivity Development:
Developing sensitivity to the feedback provided by the disk is a skill that improves with practice. Regularly engaging in the GlassRenu process and paying close attention to the sensations and responses of the disk will enhance your ability to quickly and accurately make necessary adjustments for optimal glass restoration.

Fig. 3810A

Fig. 3810B

Fig. 3810C

Fig. 3810D

In the GlassRenu process, understanding the feedback provided by RenuDisks and polishing felts is crucial for achieving a high-quality repair. This feedback offers insights into how the glass is responding to the restoration process, allowing for necessary adjustments. Here are some key aspects to focus on:

Fig. 3820A

Fig. 3820B

Fig. 3820C

Fig. 3820D

Recognizing the Path of the RenuDisk:
As the RenuDisk moves across the glass surface, its path should be clearly visible on the pane. Ideally, this path mirrors the full width of the disk, which is a strong indicator of the disk being mostly flat against the surface. A well-defined path ensures uniform abrasion and minimizes the risk of uneven removal or additional damage. Conversely, if the path becomes fragmented, narrower than the full width of the disk, or appears wispy, it’s a clear sign that the disk is not fully flat against the glass. This requires immediate adjustment to realign the disk for even contact with the surface.

Monitoring Glass Dust Accumulation:
The process of abrasion naturally results in the accumulation of glass dust (glass stock) within the abrasive surface of the RenuDisk. When the disk is perfectly parallel to the glass pane, this accumulated glass stock should remain trapped between the pad and the glass. However, if you notice larger chunks of glass dust dislodging from the disk during the abrasion process, it’s a telltale sign that the disk is not entirely flat against the glass. This observation is crucial as it calls for immediate correction to ensure the disk’s flatness and to maintain the effectiveness of the abrasion.

Conditioning of the Grey RenuDisk:
While the Black and Red RenuDisks used in Step One should leave a clearly defined path almost immediately, the Grey RenuDisk used in subsequent steps requires a bit of conditioning. This initial conditioning is essential for the disk to reach its full effectiveness and provide accurate feedback.

Importance of Proper Technique:
In the field of glass restoration, the significance of correct body positioning and tool handling cannot be overstressed. These techniques are pivotal not only in mitigating the risk of inadvertent damage to the glass pane during restoration but also in reducing physical strain on the technician. A key concept here is the establishment of an effective “Strike Zone.” This zone, ideally spanning from the tip of the nose down to mid-chest and not extending beyond the width of the shoulders, serves as a guideline for maintaining optimal control over the polishing equipment.

Strike Zone and Tool Control: 
By confining the movement of the polisher within this strike zone, technicians can ensure that the tool remains parallel to the glass surface, which is crucial for consistent and precise work. Deviating from this zone often leads to unintentional pressure variations and uneven contact between the Renudisk and the glass, potentially causing further damage. The strike zone concept not only aids in quality control but also enhances the safety of the operation, ensuring that the tool is handled in a controlled and stable manner.

Optimizing Movement and Reducing Fatigue:
To cover a larger working area without compromising the integrity of the strike zone, a specific stance is recommended. Technicians should position their feet slightly apart, aligning their heels under their shoulders. This wider stance, coupled with a slight bending of the knees, allows for greater stability and flexibility. This posture enables the upper body, particularly the arms and shoulders, to remain steady within the strike zone. Such positioning allows for the lower half of the body to pivot, facilitating movement across a larger area without straining the upper body.

Best Practices:
Emphasizing these body positioning and tool handling techniques in glass restoration is not just about achieving optimal results; it’s also about ensuring the well-being of the technician. Adopting these methods leads to a more efficient restoration process, minimizes the potential for errors, and significantly reduces muscle fatigue and stress. This approach underscores the importance of ergonomic practices in the field, marrying quality of workmanship with the physical health of the technician. As these practices become more ingrained, technicians will likely experience fewer work-related discomforts and greater overall job satisfaction.

Fig. 3130A

Fig. 3130B

Fig. 3130C