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
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
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
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
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
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
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.