Fish Glue? Bake in oven at 800 degrees?

[William Holohan]

OK....I'm sitting there watching "Antiques Road Show".... Lady has really nice reverse painted dome shaped lamp shade....The lamp was under it too, but I wasn't interested.... Lamp and shade were from the early twenties....
The appraiser tells her all about the reverse painting and then gets to the outer finish details....that went something like this....
"They first sandblasted the outer surface....(OK so far) Then they covered it with fish glue....(Huh, what did she say? Fish glue?) Then they placed it in an oven and baked it at 800 degrees until the fish glue dried and pulled off little pieces of glass to give it that textured surface"....
My question is: Is her description accurate, or is the a case of "The story changes a little every time it is told" and she was the last one in a long line of listeners????
Alright, I Lied...I have one more question.
Is it possible that she had some info that may have been accurate??? The reason I ask is the chip was not like any I have seen before. The easiest way to describe it is that it appeared that the glue had crackled like "crackalure" paint before it chipped. Very nice effect.
OK, this windy old geezer is done now....

[Mike Jackson]

http://aic.stanford.edu/sg/bpg/annual/v19/bp19-29.html

I did a quick search for Fish Glue. Looks like it has been around for a long time and is similar to Hide Glue, but more readily absorbs water again. You can do a search and read more about it, but I suspect the Roadshow guy just mixed up the glue types. Maybe they DID use it, but if it takes an 800 degree oven, I doubt many of us would have the resources. Rick had a Kiln for slumping the glass labels and I wouldn't have put it past him to try it out.

At one of the Conclaves, Rick had a food dehydrator out and had just chipped a small test panel, maybe 5" x 5". It had a very distinctive chip pattern, similar to what you describe.

Mike

[Patrick Mackle]

Like William I too perked up when the appraiser mentioned fish glue and 800 degree heat to achieve the distinctly different chip finish on the Handel lamp shade.
Apparently there are 3 types of glue touted to have the ability to chip glass. Animal hide glue, rabbit skin glue, and fish glue. Personally I have only done EXTENSIVE tests with animal glue. I know that it has certain properties that can be controlled or manipulated to produce different patterns or effects. Some effects can change depending on the mixture of glue, thickness applied, and number of times the batch is reused. It makes perfect sense that gelatin protien from other animals could produce significantly different patterns/results. The problem I have is the 800 degrees mentioned by the appraiser. I would think that the glue would have dried and chipped the glass off at a much lower temp. I have a good suspicion that the shade was heated to 800 degrees primarely to bind the glass enamel colors to the inside of the shade, and in the same firing process the fish glue was along for the ride chipping at 150 deg. and vapourizing at around 600 degrees. I think that the information she was repeating on the original process was not clearly recorded.
Pat

[Larry White]

Hey Pat... turn off the TV and get back to work.

-LW

[Kent Smith]

I caught the show too while waiting for something better to come on PBS. I agree with Pat but I also wonder if she was confusing slumping the shade to shape not to mention firing the colors with the chipping process. I have found that most people do not understand anything about the chipping process. I have used fish glue for gilding on paper and parchment but I think it would be too lightweight to chip glass well. Unless it is in de-humidifying conditions it absorbs too much moisture from the air to shrink enough to chip the glass. I also suspect that fish glue may not adhere well enough to the glass to chip even if it would shrink enough.