How To: Remove Suction Cup Rings from Glass
Before You Begin > Step One: Cutting > Step Two: Polishing > FAQ/ Troubleshooting
Suction Cup Rings
Suction Cup Rings
Damage Category: 1
Approx. Time/Sq. Ft.: 3 – 5 minutes
Suction Cup Rings on glass surfaces are a faint but discernible imperfection, often encountered after the use of suction cups on the pane. The result is a slight but noticeable alteration in the glass’s surface appearance, which may affect both its aesthetic and optical qualities.
Suction Cup Rings are easily removed using GlassRenu’s Cutting Compound, Foam Finishing Disks, Polishing Compound, and Polishing Felts.
Before you Begin
| Workspace Checklist |
|---|
| Power Access |
| Workbenches, ladders, scaffoldings, lifts, etc. |
| Masking Tools |
| Drop Clothes/ Tarps/ Waste Receptacles |
| Temperature management tools |
| Damage Assessment Checklist |
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| Confirm Glass Type |
| Confirm Damage Type |
| Inspect Glass System Integrity (Framing, Glazing, etc.) |
| Inspect Glass Pane Integrity (Cracks, Chips, etc.) |
| Identify damage location(s) |
IMPORTANT NOTE: During the glass restoration process, it’s crucial to closely monitor the temperature of the glass pane. The heat generated from grinding or polishing can increase the risk of thermal stress, potentially leading to cracks or breakage. To effectively manage this risk, it is recommended to use a non-contact thermometer, a tool available at most hardware stores. This allows for accurate and safe temperature measurements without interrupting the workflow.
Regular monitoring of the temperature differential between the repair area and the rest of the pane is key to preventing thermal damage. Should the temperature in the work area rise significantly, pause the restoration and allow the glass to cool. Immediate cessation of work and allowing the pane to return to a normal temperature range is necessary if overheating occurs. For specific temperature guidelines and detailed procedures on managing thermal expansion, please refer to section C 3.1.1.0 – Thermal Expansion.
| TEMPERATURE ADVISORY | Delta | Maximum Temperature |
| Annealed | +80℉ Δ | N/A |
| Tempered | +120℉ Δ | N/A |
| Laminate- Annealed | +80℉ Δ | 145℉ |
| Laminate- Tempered | +120℉ Δ | 145℉ |
| Mirrored | +80℉ Δ | N/A |
Suction Cup Rings-
Step One: Cutting
- Secure a Foam Finishing Disk to the designated backing pad.
- Apply 1/4 – 1/2 oz. of Cutting Compound to the surface of the Foam Finishing Disk.
- Adjust the polisher to operate at a rotational speed of 600 RPM.
- Align the Foam Finishing Disk surface directly above the glass’s damaged area, ensuring that the disk remains parallel to the glass pane.
- Engage the polisher’s power trigger, and trigger lock.
- Employ a systematic cutting approach by guiding the RenuDisk in alternating horizontal and vertical paths across the damaged area. This action should form a precise cross-hatch pattern. Maintaining uniform pressure, continue cutting until all heat haze has been removed.
- Disengage the Foam Finishing Disk from the glass pane.
- Disengage the polisher’s power trigger. Ensure the disk is stationary.
- Detach the Foam Finishing Disk.
- Continue to Step Two: Polish.
NOTE: Over the course of cutting, it may be necessary to reapply Cutting Compound to the Foam Finishing Disk. If the Cutting Compound has been fully worked into the glass, or if the Cutting Compound becomes dry on the pane:
– Disengage the polisher, ensuring the disk is stationary.
– Apply 1/4 – 1/2 oz. of Cutting Compound to the surface of the Foam Finishing Disk.
Step Two: Polish
Step Two: Polish utilizes the Polishing Felt and Polishing Compound to restore glass to full luster.
- Secure the polishing felt to the designated backing pad.
- Using the rasp file, abrade the polishing felt surface gently. This helps elevate the natural fibers of the felt for enhanced polishing ease and efficiency.
- Vigorously agitate the bottle prior to each application to ensure homogeneous distribution of the polishing compound. Apply Polish Compound directly to the felt’s surface.
- Adjust the polisher to operate at a rotational speed of 600 RPM.
- Align the polishing felt surface to overlap the top left corner of the established work area by approximately ½ the diameter of the polishing felt, ensuring that the disk remains parallel to the glass pane.
- Engage the polisher’s power trigger, and trigger lock.
- Disperse the polish uniformly across the entirety of the work area.
- Employ a systematic polishing approach by guiding the polishing felt in alternating horizontal and vertical paths, expanding the established work area created in Step Two by approximately ½ the diameter of the RenuDisk. This action should form a precise cross-hatch pattern. Maintain uniform pressure. Continue the polishing process until all of the Polishing Compound has been worked into the glass.
- Inspect the entire work area, checking for any remnants of haze from multiple angles. Pay particular attention to the edges and corners of the work area. If any remnants remain, begin Step Three again.
- When the pane has been adequately restored, clean the glass using any standard glass cleaning technique to remove excess Polishing Compound.
FAQ
Step One: Cutting – FAQ
What speed should I run the polisher during cutting?
Set the polisher to 600 RPM for initial cutting. This keeps control high and limits mess. As the compound begins to dry out, you can increase speed up to 1200 RPM if needed to maintain smooth motion.
What’s the correct movement pattern for cutting?
We recommend a left-to-right motion, dropping down by half a disk width with each pass, followed by a right-to-left pass—forming a box grid. Then reverse upward to complete the area. This consistent pattern helps maintain coverage and uniformity.
How do I apply Cutting Compound correctly?
Apply ¼ to ½ oz. of compound directly to the Foam Finishing Disk before starting. Reapply as needed if it begins to dry out or lose effectiveness.
How can I tell when the damage is fully removed?
Continue polishing until all signs of the imperfection are gone under multiple lighting angles. If unsure, clean the glass surface and inspect carefully—some marks are only visible under certain conditions (e.g., rain, condensation, glare).
Do I need to use pressure when cutting?
Yes. Apply firm, consistent pressure throughout the cutting process to ensure full contact and effective material removal.
What if the Cutting Compound dries mid-process?
It’s okay to polish dry—GlassRenu compounds remain effective without reapplication, but they will cut more slowly. As long as there is polish on the glass, it’s okay to keep polishing—reapplying is always recommended.
Should I clean the disk during use?
Generally no—but if buildup occurs, you can rinse the Foam Finishing Disk with water. Its porous structure allows for safe cleaning and reuse.
Is it possible to overwork a Category 1 repair area?
No. GlassRenu compounds are formulated for polishing glass. There’s no risk of overworking or damaging the surface during CAT-1 repairs.
Step Two: Polishing – FAQ
What speed should I polish at?
Start at 600 RPM to avoid flinging polish. As the compound begins to dry, you can increase speed up to 1200 RPM to maintain performance.
How do I prep the Polishing Felt before use?
Use a rasp to gently abrade the surface. This lifts the fibers, improves absorption, and enhances polishing efficiency.
How much compound should I use?
Begin with ¼ to ½ oz. in the center of the felt. Reapply when the pad starts to dry or drag across the surface.
What’s the right technique for polishing?
Use the same box-grid pattern as in cutting: left to right, dropping by half a disk width, then right to left—repeating as needed. Always use firm pressure and keep the pad flat against the glass.
What should I expect the glass to look like after polishing?
You should see full reflectivity and clarity, with no visible marks or haze. The polished area should seamlessly match the surrounding surface.
The imperfection is still visible after polishing. What now?
Reevaluate Step One—if the defect wasn’t fully removed during cutting, go back and re-cut the area before polishing again. If damage continues to persist, severity may have been misdiagnosed.
Can I reuse the Polishing Felt?
Yes. Rasp the pad clean between uses. Replace it when it becomes matted, hardened, or ineffective.
What if polish is flinging everywhere?
This typically means:
– Too much compound was applied
– RPM is too high
– The pad wasn’t fully seated before activating the polisher
Do I need to clean the glass after polishing?
Yes. Use standard glass cleaner or a clean microfiber cloth to remove residual compound and inspect the final result.
General Process – FAQ
What qualifies as Category 1 damage?
Category 1 includes faint, surface-level imperfections that can be seen but not felt, such as light mineral deposits, surface rubs, or environmental residue. These do not require abrasive disks for removal.
Is this damage actually in the glass?
No. Category 1 damage is strictly on the surface. These imperfections can typically be removed through cutting and polishing with the appropriate compound and tools.
What causes surface-level imperfections like these?
They can result from water deposits, light contact, residue buildup, suction cups, or embedded debris (like rubber particles) reacting with the glass surface.
Can this process be used on coated glass (e.g., Low-E or hydrophobic)?
Yes, but be aware: restoration may remove some surface coatings. Test a small area first or check with the glass supplier if coating retention is required.
Can I restore laminated or insulated glass units (IGUs)?
Yes—if the damage is on the outermost surface. Avoid edges or seal areas, and always monitor heat buildup to prevent seal failure.
Do I need to monitor temperature during CAT-1 jobs?
Absolutely. Even light restoration can generate heat. Use an IR thermometer and follow standard thermal expansion guidelines:
– Tempered: Max +120°F differential
– Annealed: Max +80°F differential
– Laminated: Max 145°F absolute
What if the damage doesn’t fully come out?
It may not be surface-level. Permanent etching or defects beneath the surface won’t respond to polishing. Always test early and set expectations accordingly.
Should I mark the work area before starting?
Yes. Even in light restoration, marking the area (e.g., with dry erase marker or tape on the reverse side) helps maintain a clean blend zone and avoid unnecessary expansion.