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Tim Puro writes:
At the May 2003
National Center for Woodfinishing Technology Conference,
Bruce Sventek from 3M demonstrated his company's
Glass Defect Repair System.
The system can be used to remove scratches from window glass,
glass topped tables and architectural glass.
Here are some pictures from that presentation
and a description of the process.
You can find instructions for the
3M Glass Repair system on the web at:
http://www3.3m.com/search/
type in TRIZACT,
and then 3M(TM) Glass Defect Repair Instructions,
60-4400-4250-9 [PDF 38 KB]
The system uses a variable speed rotary polisher/sander.
Bruce indicated that it's important to use a rotary tool on glass
because a random orbital tool will not leave a smooth surface.
The tool Bruce used for the demonstration is shown below
equipped with a special quick change backup pad
to accept the special PSA Trizact abrasive discs.
You can buy an adapter kit (described in the Glass Defect
Repair Instructions) to convert a Makita or Milwaukee polisher
to accept the quick change back up pads.
3M recommends that you have one quick change back up pad
(shown below) for each of the four levels of abrasive pads and
the white pad that is used with the 3M polishing compound.
You can buy higher end rotary polishers that feed water onto the
surface through the hole in the backup pad and the abrasive pad.
For the demonstration, Bruce used a machine without the fancy
water spritzing feature and used a plant misting bottle to spray
water on the glass to lubricate the repair and help keep the glass cool.
Bruce started repairing a scratch on plate glass by using a pink
A20 micron grade pad. He sprayed the surface with water and
worked the tool in a back and forth motion to remove the scratch.
The tool was running about 2000 rpm.
The weight of the tool on the glass was sufficient to do the work.
Bruce did not significantly bear down on the tool.
After removing the scratch with the pink pad, Bruce moved on
to the blue A10 micron pad. This time he worked the tool in a
back and forth motion 90 degrees to his original scratch pattern
and he made the repair pattern a bit wider.
Water is still being used to lubricate the glass.
When the blue pad removed all the scratches left by the pink pad,
Bruce moved on to the orange A5 micron grade pad.
The orange pad does not grind as much as it polishes.
Using water as a lubricant, this time he moved the tool
in a rotary motion. Again, with each successive grit,
the repair area gets wider as you try to "feather out" the repair.
Finally, move on to the white pad
and use the Glass Polishing compound to finish the repair.
The picture below shows a seminar participant looking through the repair.
While it's difficult to see, the glass is distorted somewhat from the repair.
But for most table top or window glass applications,
the repair would have been more than adequate.
Bruce noted that before you do work for a client, get a disclaimer
or waiver signed for any damage you may cause to the glass.
The repair process generates heat and heat can break the glass.
Some heat is OK, but if the glass is too hot to touch, it's too hot to work on.
Tim Puro
Bloomington, Indiana