For decades, scrapers have been used by the window cleaning, glass,
and building industries. Many millions of scrapers have been sold by
suppliers to these industries, and to homeowners.
Scrapers, which won’t scratch uncoated glass when properly used, have
long been the standard and most practical method for removal of debris
such as paint, adhesives, or stickers from uncoated glass, not only
during construction cleaning, but throughout the useful life of the
Scraping is still the most practical method for removing certain types of construction debris.
Scraping is often the only practical method that will yield a perfect result.
Glass scrapers do not scratch uncoated glass when properly used.
Scratched tempered glass has become a major issue in recent years. It
has become apparent that most of the problem is due to a microscopic
defect called fabricating debris.
Fabricating debris consists mostly of tiny glass chips and glass dust
that get baked onto the surface of some tempered glass. These surface
defects, also known as glass fines, may create scratches when they are
dislodged and trapped by a scraper during window cleaning.
Tempered glass scratches caused by fabricating debris have distinct
characteristics, and should not be confused with other types of
scratches. Fabricating debris scratches are typically finer and more
numerous other common scratches. See the section on Field Identification
of Fabricating Debris Scratches.
Window glass in general is more technologically advanced than it was
20 years ago, but fabricating debris on tempered glass is still a
quality issue, not a technological advancement.
Fabricating debris is not a theory - it is a fact that even the glass industry does not deny.
The glass industry has taken a new position in recent years - that scrapers should no longer be used to clean glass.
The IWCA's official position was published in June, 2004 - the "IWCA
Tempered Glass Informational Bulletin 2004 - Scrapers & Fabricating
The IWCA advises window cleaners not to accept responsibility for finding fabricating debris defects on tempered glass.
The IWCA recommends testing tempered glass for fabricating debris
prior to installation. Builders can test tempered glass when it is
delivered, or fabricators can test as part of their quality control
Random testing of tempered glass for fabricating debris may confirm
the presence of fabricating debris, but can not confirm the absence of
fabricating debris on a jobsite.
Thorough testing might involve actually trying to cause fabricating
debris scratches on each tempered window with a scraper, using bright
lights to locate scratches, and then using magnifiers to confirm that
they were fabricating debris scratches. This can take hours, and
obviously cannot be done if the objective is to avoid scratching the
The IWCA recommends a tempered glass scratch liability waiver for all
construction window cleaning contracts, and for maintenance contracts
when significant scraping will be done. This advice is sometimes
misunderstood. The builder signs a tempered glass scratch liability
waiver to assure that they will not blame the window cleaner for
scratches due to fabricating debris on tempered glass, and will not
force the window cleaner to prove that fabricating debris caused
scratches on tempered glass. The IWCA website - www.iwca.org has an
example of a Cleaner to Builder liability waiver.
The IWCA suggests that builders require suppliers to provide quality
tempered glass that can be cleaned - without scratching - the same as
glass which is not tempered. The IWCA website - www.iwca.org has an
example of a Builder to Supplier waiver.
There is never a benefit to fabricating debris, because it makes
tempered glass harder to clean and more susceptible to scratching.
Builders who realize they have a choice would never choose tempered
glass with fabricating debris issues.
When construction window cleaners are asked to use alternative methods
instead of scraping, the result is often not satisfactory. And often
this only postpones the day that an unsuspecting homeowner or another
window cleaner will have to deal with fabricating debris scratches.
If construction window cleaners are asked to reduce scraping to a
minimum, they should still require the builder to sign a tempered glass
Often, reduced scraper use only postpones the day that an unsuspecting
homeowner or another window cleaner will have to deal with fabricating
debris scratches on poor quality tempered glass.
Plastic scrapers are not recommended. If fabricating debris is
present, it may become embedded in the plastic and scratch every window
the blade touches from that point on.
Protecting quality glass surfaces during construction is desirable,
but protecting poor quality tempered glass will not prevent future
problems with fabricating debris scratches.