Posted by Bob Rochon on February 29, 2004
Robare M. NovouAhh you gotta love failures, they can teach so much. I just chipped my second panel yesterday, it was a small test piece, regular plate glass.
I frosted it with glass beads, for I had access to a small blasting cabinet that uses glass beads for cleaning parts for small engine repair. I have a small sandblaster but this past week it was too cold to blast outside.
Anyway, my end result was less than say desirable, the glue chipped off completely for the table was even and I had excellent moisture control, I used my light table and just a card board box over the glass to contain the chips.
So here is my dilema, the glue didn't grab a LOT of the glass, so I have more frosted areas than actual glass chips.
Now comes the millions dollar questions, lol Do you think the glass beads didn't etch the glass enough to hold or maybe the fact that the blasting cabinet I used was also used for cleaning engine parts, I contaminated the surface?
Any help would be great. Thanks
Mike JacksonGlass beads? Ive never used glass beads, but Im thinking thats something used to polish and not to scratch the surface your blasting it with.
I remember a similar situation, where a friend told me to use his blasting cabinet...he used small round shot...for polishing metal parts.
No...that won't work either. You want a nice frosted abraded surface with some tooth. I made that smooth frosted surface with the acid thinking that had tooth...no such luck, ended up blasting it with sand...like I should have done to start with.
When I did my first glue chipped piece, I laid it on about a 1/4" thick, man was that a mistake...it dryed leather like and curled up at the ends with no chipping. It was like someone laid a piece of toast on the glass. Lesson learned,too thick. The next one was too thin, as I laid it on about 1/16 of an inch thin...it dryed and that was it, no chipping...not enough glue to out muscle the glass and chip it. So I laid on the glue about an 1/8 of an inch thick....watched it go from a soft cloudy tan gelatin(that you could dent with your finger nail)to a hard transparent tinted tan (that you could not dent with you finger nail)for the first stage...than placed it in the hot box for the chipping to begin. 3rd times a charm!
RMN
Bob, You are at the "double chip" stage on this one! If you were able to use the previous stencil or if you did the asphaltum method, you could still pour glue again and get the double chip look.
I can't say much about the glass beads. I never used anything but silica sand or silicon carbide and both worked. There might have been some contamination from oily beads? If I were doing that again, I'd clean the glass with laquer thinner or acetone, followed by pure amonia to remove any traces.
One last tidbit worth mentioning...
The glue starts out as granules, dissolved to an oatmeal texture, heated to liquid syrup, poured and then cools to a soft geletin texture. You MUST let the water in the leathery geletin texture to completely evaporate before exposing the glass to heat. In other words, it has to become rock hard on the glass before it begins the chipping process. It is possible for the skin to dry before all the under film and if you expose it to the light table or heated cabinet, the top layer can chip off leaving frosted glass.
Lastly, as Pat mentioned earlier, another big No-No is not having enough of a layer of glue. It just doesn't have the power to lift off a good layer of chipped glass.
It is impossible for me or anyone to positively identify the problem, but it more than likely is one or more of the issues above. I'd guess it is a little of all of them!
Mike
Bob Rochon
Mike JacksonI think you hit the nail on this one Mike, see I didn't let it dry hard before I put it on the light table, and being the overzealous anal type that I am I added a heat lamp just to " be sure" ha. And oh in about 10 minutes I noticed the glue re-liquifying and the edges appeared dry and the centers where pulsating like a living heart. ( that was cool by the way ). I did remove the heat lamp but the damage was already done. So seeign as these are just test pieces, I cleaned off the asphaultum and I'll keep this one as an example of what NOT to do....again ( sigh )
One thing I was excited about is I got the humidity down to less than 25% and the light table seems to work without building a box.
Bob,
By the time you make all the normal mistakes (being in a hurry is one), you'll eventually figure it out. The process is not hard at all, but it takes some discipline!
Mike
Denver Chapter of the Letterheads