Separating bonded glass

[mmerig]

The front lens on a Kenwood tuner (manufactured mid-1970's) was damged during shipping to me. It is two pieces that are apparantly bonded together. I'd like to re-use the smaller, intact piece but I need to separate the bond. Anyone know if heat or solvent will separate them?

[dave_gerecke]

Hello mmerig, I am sure that some sort of solvent or some application of heat will weaken the bond between the two layers. Just be careful and make sure you only do one of the two at a time. If you use a solvent that is flammable and apply sufficient heat, you may reach the flashpoint of the solvent and it will self ignite without any open flame. This is what is referred to as the lower explosion limit (LEL) in the hazardous waste field.
So, if you try the solvent first and it doesn't work, rinse the solvent off with water and wait until it drys, then try the heat and see if that works. It's quite possible that you could put the whole thing in a container of water for a while (days) and it might loosen the adhesive that way.
Unfortunately, without knowing what kind of adhesive was used, it's hard to say what will or won't work. If I knew the adhesive, I could find people where I work with the information. The company I work for makes machines to bond semiconductor wafers together.
If you have a decent university in your area, you may be able to find a helpful person in the chemistry dept. that can help you do this safely. They tend to have a good supply of solvents, and they have a good collection of heating devices.

Peace,

Dave

[mmerig]

Thanks for tha advice. I tried the heat method, placing a metal tray with sand on my wood stove and putting the glass on the hot sand. My house got really hot, depsite an open door an -5 egrees C outside, but the bond did not break.

I'll try boiling water next.

I could just get another piece of glass for later bonding, but I did not want to waste the one that fits just right.

[Cal Weldon]

I have done my share of removing adhesives. If they have used a pressure sensitive adhesive, household ammonia may work. Not sure how you get it in there though. The stuff I was removing was on the surface. Good luck and let us know.

[SY]

Water won't do it. If the adhesive is a cyanoacrylate, a long acetone soak may work (but well away from any ignition source!). If it's PMMA, you'll have to get more aggressive, and a session with methylene chloride might be necessary. The latter should ONLY be undertaken by someone who knows how to handle explosive carcinogens.

[mmerig]

Thanks Sy. I was aware of these two chemical treatments, but I did not want to use them, especially the methylene chloride. I may just cut another piece of glass and bond it myself, if I can find a good (i.e., cheap, easy to use) bonding material.

By the way, boiling water did not work, except at a corner where the layers may have been a little loose from the fracture.

[Pjotr]

Hi,

Glass can stand easily 200 deg C. Bonds usually not. Try your kitchen oven, maybe it is hot enough to break the bond?

[mmerig]

The next time we bake something, I'll put the glass in afterwards at high heat and see what happens.

The sand layer on my wood stove got very hot, (400 degrees F, I guess) but the oven may be a little hotter.

[mmerig]

I placed the glass in a 260 degree C oven for about 45 minutes. I suspended the narrower glass piece from the wider one so that it would fall away (just a few millimeters) from it once the bond broke.

The bond never broke, and I tried prying the glass pieces apart with a knife while they were still in the oven.

Apparently, the bond is quite heat resistant.

I am going to get another piece of glass.

Thanks for the help.

P.S. Any recommendations for a clear glass-bonding agent?

[john blackburn]

Shpoop might be the one to ask about gluing glass together.......

My newest speaker (/amp) project

He seems to have a fair bit of experience with glassworking