Glue Chip Glue?

[Bob Ficucell]

Does anyone know if glue chip glue goes bad? ie won't chip .
I got some from Rick, mixed it the same low humdity, even used a heat lamp, just barely started to chip in one corner.
Thanks. Bob

[Patrick Mackle]

When well kept in its dry granular state it will probably last forever like an Egyptian artifact.
Things that will cause it not to chip are things like overheating it, as well as applying it too thin or too thick.
Another factor that can affect the chipping action is the preliminary dryness (water content) of the glue as it is moved from the ambient air into the warmer dehumidified chipping area.
The pulling off of the glass by the glue is actually a mechanical process in which the glue begins to work as two separate layers. The initial drying allows the glue to bond to the glass, but still contain a significant amount of water. The second drying stage is more aggresive and causes the surface layer of glue to to shrink and contract faster than the glue beneath it. The upper layer literally acts like a pry bar acting against the glue that has bonded to the glass, causing it to curl and pull the bonded glass along with it. Once you get a sense of the proper deposit of dried glue per square foot and the proper water content to move it to the next drying stage, it will become clear to you how the process works.
The glue acts very much like a sponge, able to swell and soak up a large amount of water, then to lose it all, shrink up and become bone dry. Also, just like a sponge, that chipped glue can be used over and over.

Pat

[Kent Smith]

I have found that chipping failures happen most often when the dehumidifying acceleration process is begun too soon as Pat has alluded to. One must allow the bond to complete itself, in the gelatenous state before the drying process begins. I have the best results when my blasting etch is complete and smooth and when I allow the glue to set for at least 10 hours to ensure good adhesion. This requires keeping it in a fairly humid area, a real feat in my climate and then allow it to dry, causing the chipping. Much like Pat's sponge annalogy, I think of the glue as being more like a chamois, to be used over again. As to temperature, if the glue is too hot, it will result in a thin application which may not have the strength to adequately chip the glass. If the glue is too cool, it will not only be thick but it will gel too soon and consquently not adhere to the glass. The thick mixture also will not dry sufficiently to fully shrink enough to chip.

Steve B used to say this process only works consistantly because of a little black magic and a lot of luck. This also appies to using enamels and Japans on the many surfaces that we do and expect them actually to last.

[Bob Ficucell]

Thanks guys for the help.
I'll give those ideas a try and let ya know. Bob

[Sarah King]

I've been investigating the glue chipping process too, so I asked my neice who is a micro-biologist about the proteins in the glue and I thought her reply was very helpful. She wrote:

Imagine each protein molecule as a coiled spring covered all along it's length in suckers (electrostatic bonds). The suckers want to be stuck to something and if there is nothing else around they will stick to each other, turning the spring into a tangled blob. When the protein is heated (melted), the suckers release. When the protein is wet, the spring relaxes. So a warm, wet protein is very relaxed and not bound to anything. As the protein cools, the suckers stick to whatever is available. As the protein dries, the spring tightens and shrinks – it returns to its native state.

Glue Stage Temperature Humidity The “springs” The “suckers”
1. Store Cool Dry Tight Closed Closed
2. Soak Cool Wet Loose Closed Closed
3. Melt Warm Wet Loose Open Open
4. Apply Warm Wet Loose Open Open
5. Gel Cool Wet Loose Closed Closed
6. Chip Cool Dry Tight Closed Closed

I had this as a nice little table but I can't figure out how to paste it into thie post. I hope you can understand it. I think it shows why it is important to apply the glue to warm glass - you can keep the proteins all relaxed and the bonds open.

As Pat says, you can re-used the glue any number of times since all you are doing is expanding and contracting the proteins. The only secret to reusing the glue is to get the weight of glue and water right. It is two parts water to one part glue by weight. When the glue is not in its original granular form, measuring by volume doesn't work.