Posted by Bob Rochon on December 01, 2003
I recently this past weekend spent some time doing a small glass meet at Cam Bortz's shop and we worked on some sample / test panels for chipping.
The top and bottom of the panel had some 2" letters that we wanted to chip the inside of the letters and around the letter with only an 1/8" outline between the chipped part.
What we discovered was on one panel where the asphaltum was a bit thinner the glass disregarded the asphaltum area all together for the most part and bridged the chpped areas together.
On another panel of the same design, the asphaltum was dark black and it held up alomost 85% but we still experienced the chips going right across the 1/8" outline.
Is this too thin of a gap between chipped areas?
If not, how could we prevent this from happening again?
Any help would be greatly appreciated and I thank you in advance.
Mike Jackson
Bob,
Sounds like part of the problem is your care in applying the glue. You have to apply the glue a bit away from the edge of the asphaltum line and let it creep towards it and stop.
I think you can see in Jeff Lang's photo above that it is easily possible to protect lines finer than 1/8". Just to be safe, IF and WHEN we saw a line that had been bridged by the glue, we simply cut it and removed the glue causing the bridge.
Hope this helps!
Mike
Larry White
Darryl GomesI would agree with Mike. An 1/8" clear space would not be too thin, I've had success with even thinner. The art is in the application of the glue. Allowing the glue to flow up to the asphaltum edge and stop is the best bet. Over the years I've learned that the number one thing in precision glass work is to thoroughly inspect every step and process. After applying the glue and allowing it to gel, go back and inspect for any bridges over the asphaltum. Trim and remove these with an x-acto knife. I like to remove any glue over the asphaltum by more than 1/8". A habit that I've developed is to bisect every angle that is 90 degrees or less with a small 1/8" score. I find that this helps the glue "roll" away from the point of the angle keeping it nice and sharp. Otherwise the glue can have a tendency to chip right over the sharp point that you want to keep. Oh, and, always remove the stencil after blasting and prior to glue application. Using the stencil to flow the glue up too is an invitation for massive plinkage and disappointing results.
-LW
I normally chip using paint mask as a sandblast resist, directly on the glass, no asphaltum. I can pour the glue on very quickly and spread it to a uniform thickness with a vinyl squeegee. I let it gel and then cut it and remove the mask.
I find that this works well for larger, less intricate patterns as the cutting could get tedious on small letters.
I always cut my corners 90º or less as well to stop plinking.
Darryl Gomes
Larry White
I like the double cut method too. One nice thing about it is you get a uniform thickness of glue over the entire design. I think it chips better right up to the edge of the sandblast. When you flow the glue up to an asphaltum edge, the glue naturally "rounds off" up to that edge, the glue is thinner and weaker and leaves more sandblast at the edge of the design.
-LW
Denver Chapter of the Letterheads