Customer Reports Scratches After Clean: Pre-Existing vs Debris Translation Decision Tree

Why this matters

A scratch claim is a liability event, not just a quality complaint. Replacing a large tempered or insulated pane is expensive, and the claim usually arrives days after the job when memory and evidence have faded. The core dispute is whether your service caused the scratch or merely revealed scratches that pre-existed on glass that was too dirty to see them. A second, real mechanism is fabricating debris: microscopic particles fused into tempered glass during manufacturing that any scraper, even used correctly, can dislodge and drag, scratching the glass. Translating "you scratched my windows" into the actual cause determines whether you owe a replacement, owe a disclosure, or are looking at a known glass defect. This tree separates the three and tells you how to confirm each before you concede or deny.

Symptom presentation

Get the claim specific and photographed in raking light. Note: are the marks fine hairline lines, deeper gouges, a cluster, or a single long scratch. Note the direction relative to how the glass was cleaned. Note whether the marks are on tempered glass (look for the manufacturer's etched stamp in a corner) and whether a scraper or razor was used on that pane. Note whether the customer saw the marks before the clean. Scratches that follow scraper-stroke direction on tempered glass are the fabricating-debris signature; random multi-directional scratches the customer never noticed are the pre-existing signature.

Quick checks

• Confirm whether a blade or scraper was used on the affected pane. No scraper used means a non-scraper cause (existing damage, abrasive cloth, grit).
• Identify the glass type. Tempered glass carries fabricating debris risk; the manufacturer's bug/stamp confirms tempered.
• Examine direction and pattern in raking light. Unidirectional and aligned with scraper strokes versus random and multidirectional.

Isolation tree

Branch 1: No scraper or razor was used on the pane, and the marks are random and multidirectional. These are almost certainly pre-existing, exposed when the dirt film was removed. Dirty glass hides fine scratches; clean glass shows them. The customer's first clear view of their clean glass is when they notice damage that was always there. This is a translation issue, not a cause-and-effect from your work. Confirm with the customer that you used no abrasive on that pane.

Branch 2: A scraper was used and the glass is tempered, and the scratches are fine, unidirectional, and align with scraper strokes. This is fabricating debris: hard particles fused to the tempered surface during heat-treating, which a scraper, however correctly used, can catch and drag across the glass. Industry guidance recognizes that scraping tempered glass carries this inherent risk regardless of technique. Liability here is shared and contested ground; the IWCA position is that the defect originates with the glass, but practical resolution depends on your scrape policy and disclosures.

Branch 3: A scraper was used and the marks are deep, gouged, or clearly tied to a dragged piece of grit, or an abrasive pad or dirty cloth was used. This is a technique-caused scratch: a blade dragged over grit, a worn or chipped blade, scraping dry glass, or a scrubbing pad with embedded debris. This is your cause and your liability. Confirm by inspecting the blade for nicks and recalling whether the glass was wet and pre-rinsed before scraping.

Branch 4: Marks are on the inside or far surface, or between panes. Not caused by an exterior clean; pre-existing or interpane.

Confirming diagnosis

• Pre-existing: no abrasive used, random multidirectional pattern, customer cannot confirm the marks were absent before. Photograph and document.
• Fabricating debris: tempered stamp present, scraper used, unidirectional stroke-aligned scratches. This is a recognized glass-manufacturing defect; document the tempered stamp and the stroke alignment.
• Technique-caused: deep gouges, blade nicks, dry-scrape or grit evidence. Own it.
• Always inspect the actual blade and recall the wet-scrape sequence; a clean wet pane scraped with a fresh sharp blade rarely scratches non-tempered glass.

Why documentation decides the claim

A scratch claim is won or lost on evidence, not argument, because the dispute is about a state that existed before you arrived and cannot be re-observed once you have left. The single most valuable protection is a pre-clean condition note: photographing existing glass damage at the walkthrough, before any work, converts a later "you scratched it" into a documented "this was already here." Without that record, you are left arguing direction and pattern after the fact. The second protection is a written scrape policy the customer acknowledges: stating you will not scrape tempered glass, or will only scrape with a signed acknowledgment of the inherent fabricating-debris risk, moves the tempered-glass branch out of dispute before it starts. The IWCA recognizes that scraping tempered glass can dislodge manufacturing debris and scratch the surface even when the scraper is used correctly, which is why a disclosure, not a denial, is the durable position. Treat every scratch claim as a relationship and an insurance event at once: document, photograph in raking light, and notify your carrier early.

Remediation

Pre-existing: disclose with photos that the marks predate and were merely revealed; you are not liable, but handle it as a relationship, not a fight. Fabricating debris: this is why a written scrape policy matters; many cleaners refuse to scrape tempered glass or require a signed acknowledgment of the inherent risk before scraping any glass. If debris-caused, point to the glass defect and your disclosure. Technique-caused: this is your replacement to fund; report it to the customer and your insurer promptly. Going forward, never dry-scrape, always pre-soak and rinse grit off before any blade touches glass, keep a sharp unchipped blade, test-scrape a corner, and avoid scraping tempered glass without a signed waiver.

References

• International Window Cleaning Association (IWCA), I-14.1 Window Cleaning Safety Standard, and IWCA published position on scraping tempered glass and fabricating debris.
• ASTM C1048, Standard Specification for Heat-Strengthened and Fully Tempered Flat Glass (heat-treating process that introduces fabricating debris).
• ASTM C1036, Standard Specification for Flat Glass (surface quality and inherent-defect reference).
• OSHA 29 CFR 1910.1200, Hazard Communication (for any abrasive or chemical restoration products used in remediation).