Official Luthiers Forum!

Moderating the amount of accelerator to eliminate the whitening is correct. IMO the best way to do this, as it is very difficult to spray a desired amount, is to spray and wait a minute or two before sticking pieces together. The accelerator has a half life and loses its intensity over a short period of time. I never get whitening doing it this way. This method lends much more control than trying to spray a certain amount of the stuff.
I love using accelerator with CA. It allows me to keep a flow going in the shop that I wouldn't have if I had to stop and hold pieces together for 30 seconds. Call me impatient but it's a dance that happens and stopping a movement stops the dance for me.

In all cases where I have encountered white CA it has been due to crazing. Internal stresses from the curing process generate microscopic cracks, and a lot of them. Slower curing formulas would help, but they are heavily filled with fumed silica, which can easily prevent a crystal clear appearance on its own. If you insist on using accelerant do not apply it to the adhesive. Apply it to the substrate (fully cured CA is okay in this case.) All the reaction needs is a basic pH at the interface. Ammonia works well, and all of the accelerator sprays contain electron donors in solvent (typically heptane.) If you take your time and allow the CA to cure naturally you will achieve the best possible result, which is as clear as acrylic.

I've never conducted experiments to validate my next idea, but I expect it would work well. Place the CA in a refrigerator overnight before use. Apply normally and allow at least 24 hours to cure. This should slow the reaction rate dramatically and allow a highly disorganized clear polymer matrix to form. I might give this a shot sometime this week. Otherwise if anyone feels like wasting the time of some people at titebond I bet they will run a similar test series. If you go that route just make sure to ask for bob and don't tell him I suggested contacting him (he hates me.)

I'll post results if I get around to running the test. BTW, it's okay to add accelerator to the surface with cold CA. The reaction will initiate although it will be very slow. It might not be a bad idea to finish the reaction using a blow dryer. It should drive the reaction towards exhaustion and relieve some internal stresses as it will soften to some extent.

Out of curiosity, would anyone be interested in having a hot glue system that extrudes a thin bead of melted acrylic plastic? It could perform at least as well as other reactive technologies but would be a thermoplastic and have good strength characteristics under a variety of stresses? If so, I have an idea in mind that would make use of existing products. Yes, this could make use of different colors as well and would be suitable for being tooled and polished after setting. So you could make exotic cast inlays... If this hasn't been patented yet I'm claiming it!

We have been involved with CA glues and accelerators for many years and have tested many types. We have found that MasterGlu Thin all purpose CA will not foam when used with GluBoost accelerator. Also, MasterCoat for dings and dents as well as instrument finishing, will also not foam or white with Gluboost accelerator. Additionally neither of these products will yellow. You can find them here. www.gluboost.com. Thanks.

Rick Rosenberg
President
Gear Up Products, LLC
www.gluboost.com

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Rick Rosenberg
President
[url]www.GearUpProducts.com[/url]
[url]www.ricksguitartalk.blogspot.com[/b][/url]
[url]www.gearupproducts.blogspot.com[/b][/url]