Baseline condition

The documented state of the glass and surrounding assembly before cleaning, testing, or restoration begins.

Meaning and boundaries

A baseline records what was observable at that time; it does not prove when damage occurred or exclude hidden conditions.

Why it matters in glass restoration

It separates pre-existing scratches, distortion, coating issues, edge damage, seal failure, and contamination from work outcomes.

Related terms

• Damage assessment
• Condition photograph
• Control area
• Post-restoration verification

References

• U.S. National Park Service — Preservation Matters: Stained Glass
  Publisher’s original source
• U.S. General Services Administration — Cleaning Historic Masonry
  Publisher’s original source
• National Glass Association — Construction Site Protection and Maintenance of Architectural Glass
  Publisher’s original source