Scratches, marks and “odd reflections” in new double glazing: what to do, what’s normal, and when to call in an independent expert
It’s a common (and understandably upsetting) moment: the new windows are in, you step back to admire them… and then you notice scratches, marks, hazy patches, ripples or strange reflections in the glass. For some homeowners it’s a minor irritation; for others it immediately feels like a major defect.
The key point is this: glass is easier to damage than most people appreciate, particularly during manufacture, transportation, site handling and installation. And, some visual effects are not “damage” at all, but inherent characteristics of modern glazing—especially when you introduce coatings, laminates, and thermally toughened glass.
This article explains:
- why marks appear,
- how to check the glass properly (using industry-accepted viewing conditions),
- common issues we see in disputes (scratches, soft-coat damage, edge defects, ghost marks/ghosting, roller wave and more),
- and how RISA inspections help resolve disagreement quickly and fairly.
First: where is the problem—outside surface, inside surface, or inside the sealed unit?
Not all “marks” are the same.
- External or internal surface marks: scratches, scuffs, silicone smears and tool marks can occur during installation or from following trades.
- Inside the sealed unit (between the panes): scratches, fingerprints, smears, debris may be trapped during manufacture and sealed in.
This distinction matters because the likely cause—and the remedy—changes significantly.
What to do if you notice anything
1) Contact your installer immediately
If you spot an issue, raise it with your installer as soon as possible. Many firms will respond quickly and resolve matters without fuss.
2) Inspect early—before follow-on trades make things worse
Damage can be caused after glazing by subsequent trades and site activity (impact, scratching, plaster/cement deposits, weld spatter, cutting tools, etc.). For this reason, checks for scratches or other damage—particularly on outer faces—should be carried out before rendering/plastering or other adjacent works, and as early as practicable after installation.
3) Avoid “DIY detective work” that accidentally causes damage
Strong lamps, close-up inspection and marking defects can escalate disputes. The accepted approach is a controlled “quality of vision” inspection.
How the industry says glass should be inspected (the part most disputes miss)
Disagreements often start because the glass is being judged under unrealistic conditions: torchlight at night, inches away from the pane, or at a steep angle.
A typical “quality of vision” approach for IGUs is:
- view in natural daylight, not in direct sunlight, with no visible moisture on the glass,
- look through the glass (not at the surface),
- stand at least 2 metres away (and 3 metres for toughened, laminated or coated glass),
- view at 90° (near normal incidence),
These principles are designed to replicate how glazing is normally experienced in use.
What is “acceptable” under Quality of Vision?
For flat transparent glass (including toughened/laminated/coated), minor blemishes can occur even in processed glass. Depending on size, location and how obvious they are at the correct viewing distance, the following may be acceptable if they are neither obtrusive nor bunched:
- small bubbles/blisters,
- fine scratches up to a limited length,
- minute particles.
The important word in real disputes is obtrusive—which is judged using the viewing conditions above.
When it’s not acceptable: contamination inside the sealed unit
If what you’re seeing is inside the cavity, the bar is typically much higher. Smears, fingerprints, dirt on cavity faces, or debris trapped inside the unit can be unacceptable if visually disturbing.
Common issues we see in scratch/damage disputes
1) General surface scratches and scuffs
Scratches can be caused accidentally by hard or sharp objects and can worsen if left untreated. Depending on severity, polishing may be possible for ordinary (uncoated) surfaces, but deeper damage increases the risk of visible distortion after repair.
Installer tip: agree a clear inspection point immediately after installation—before plastering/rendering and before other trades return to site.
2) Soft-coat low-E coating scratches
Most modern double glazed units will have a “soft” coating on the internal face of one pane to improve thermal efficiency. Soft coats can be vulnerable to scratching during the unit manufacturing process. If a coated surface is damaged, the coating cannot usually be restored, so replacement is often the only realistic outcome.
3) Edge damage (chips, shelling)
Edge damage can arise during handling, transport or installation. Depending on severity and glass type, it can also create a breakage risk—so it should never be dismissed without competent assessment.
4) Ghost marks / ghosting
“Ghosting” is the term used on for marks or patterns that appear under certain lighting or moisture conditions, often “sticker” or “sucker” marks. Some effects relate to the product type rather than damage and often need careful, standardised viewing to separate inherent characteristics from true defects.
5) Roller wave and distortion in toughened glass
Toughened glass can show visual distortions that are more noticeable in reflection, and this can be more apparent in IGUs. One common contributor is roller wave, a surface distortion created during horizontal toughening when hot glass contacts rollers.
6) Low-E “haze” and transient visual effects
Some low emissivity coatings may produce transient visual effects under certain lighting conditions. This can alarm homeowners who expect perfectly invisible glass, but it may be characteristic of the coating rather than damage.
Where RISA helps (and why an independent inspection changes the conversation)
When an installer and homeowner disagree, the dispute often gets stuck on two questions:
- Was the glass inspected correctly? (distance, light, angle, edge exclusion)
- Is what’s being seen a defect, damage, or an inherent phenomenon? (e.g., distortion/roller wave, coating effects)
A RISA inspection is designed to cut through that quickly:
- We apply industry-accepted viewing conditions and methodology.
- We identify whether marks are on an external/internal surface or within the cavity.
- We provide a clear, independent opinion supported by evidence—so both parties can make informed decisions on repair, replacement, or settlement.
For homeowners: an independent report reduces stress and gives you a factual basis for resolution.
For installers: it reduces time-consuming back-and-forth, supports fair expectation management, and provides defensible evidence where installation is not the cause.
Next steps
If you are seeing scratches, marks, haze or distortion in your new double glazing:
- notify your installer promptly,
- avoid torch-lit/close-range assessments that skew what’s “visible,”
- and if the issue becomes contested, consider a RISA independent glass and glazing inspection to move matters from opinion to evidence.
To book an inspection or discuss a concern, contact RISA and we will advise on the most appropriate next step.