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Glass Issues: Field Identification Points
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Field identification of fabricating debris scratches 

Fabricating debris scratches are caused by microscopic bits of debris that became fused to the surface of glass during tempering. The result is a surface defect that can be dislodged and dragged across the surface, possibly causing hundreds of faint thin scratches.

  • To identify fabricating debris scratches in the field, it is first necessary to determine whether or not the builder’s scratched glass problem is limited to tempered glass.
  • Use a photographer's loupe or a pocket microscope for best results.
  • Scratches caused by fabricating debris defects have distinct characteristics, and should not be confused with other types of scratches.
  • Field identification of fabricating debris scratches can be used to verify the presence of fabricating defects on tempered glass, but a higher level of proof may be required to settle claims.

If necessary, contact the IWCA for a referral to a scratched glass consultant.



Where are the scratches?

Annealed (regular, untempered) glass and laminated glass may have been scratched by other means, but these products are not processed over hot rollers in tempering ovens, so they won’t have fabricating debris scratches.

If only tempered glass is scratched, that's a red flag for fabricating debris. Read the tempering logos to see if there's more than one fabricator involved; if only one brand is scratched, that's another red flag suggesting fabricating debris.

When fabricating debris can be felt or heard when a scraper passes over a clean, scratched tempered glass surface, that's a red flag suggesting fabricating debris.

The inability to feel or hear fabricating debris with a scraper should not be considered proof that there is none present. Sometimes fabricating debris is unevenly distributed on the surface of the glass. Sometimes most of the fabricating debris is scraped off during cleaning, and very little remains.

Then determine if only the roller side of tempered glass is scratched. It is after all, the weight of hot glass on dirty rollers that causes most of the fabricating debris to stick. If all or most of the scratches are on the roller side of tempered glass, you tend to suspect that they are fabricating debris scratches.

The air side of tempered glass - the side that was not touching rollers when the glass traveled through a tempering oven - tends not to have fabricating debris issues, though there maybe a few larger bits of debris present. Scratches on the air side of tempered glass, and scratches on regular annealed glass suggest a problem other than fabricating debris.

You can usually locate the roller side by checking which type of tempering logo is present.

Typically, a pitted tempering logo - which would have been sandblasted – will be applied to the roller side.

A raised logo that can be felt with a scraper always indicates the air side. This is porcelain or "ceramic frit” – that must be applied to the air side.

There are other, newer systems for marking tempered glass, one of which is a computer controlled laser. These logos are typically sharper looking than a sandblasted logo, and a bit darker. A laser mark is normally be applied to the air side, but technically could be applied to either.


Equipment needed to examine fabricating debris scratches
10x or higher power photographer's loupe.
Often, a loupe is all you need to magnify scratches.

Available at most camera shops.
Cost: $10 and up.
30x pocket microscope will enable you to examine more scratches.
Includes a light to illuminate scratches from the side.

Expect to pay $30 for a good one.
Available from hobby shops or online
60x Shop Microscope will enable you to examine more scratches in
much greater detail, but will be more difficult to use on vertical surfaces.Includes a light to illuminate scratches from the side.

Expect to pay $130 or more.
Available online from a number of microscope vendors.

"Permanent" marking pen - used to mark the location of fabricating
debris characteristics so they can be easily located later.


Characteristics of fabricating debris scratches.

Fabricating debris scratches tend to be fairly light, often numerous and they often appear in parallel groupings.

If parallel scratches are found, check to see if the pattern is repeated. No two parallel sets of fabricating debris scratches ever show the same pattern. (If a faulty scraper was somehow causing scratches, you would expect the same pattern to appear on every stroke.)

Parallel fabricating debris scratches never start precisely where the blade is first placed against the glass. They start one at a time as a moving blade encounters and traps more fabricating debris.

Often when only one scratch is visible to the naked eye, you can use a photographer's loupe or a pocket microscope to find more nearby scratches that can't be seen with the naked eye.

These barely visible scratches will be parallel to the bigger scratch, and like the bigger scratch, they don't start where the blade was first placed against the glass. A 2nd parallel scratch is strong evidence of fabricating debris scratches.

Follow one of the scratches with the magnifier. If it is a fabricating debris scratch, one end may look like a comet. The comet‘s "head” is a larger bit of fabricating debris, broken and trapped by a scraper, creating a "tail”. Inability to find a bit of fabricating debris
at either end of a scratch is quite common. It may be necessary to observe several scratches to find a good example.

Sometimes you will find two scratches starting at the same spot. The second scratch would have been caused when the scraper passed over the same bit of fabricating debris twice. This is very strong evidence of fabricating debris scratches.

It can take a while to locate significant features. Mark each with a "permanent" marking pen, so it can be easily located later.

Those are fabricating debris scratches.

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