Some questions:
- Crazing, is that caused by the heat the Weld-On 40 generates when mixed? Any way to help keep it cooler? Should I add a fan or should I be worried about it setting too fast that way?
- Should I sand the PVC to make it bite better? Same for acrylic?
If you have any other helpful tips please share as I could get this knocked out tonight/tomorrow night. Thanks again!
Crazing is caused by stress; whether it be thermal, chemical, or physical. WO 40 does get hot, hot enough to spontaneously combust if you make enough of it; hence the recommendation to mix smaller quantities. Given the final surface area - it will cool relatively quickly so that's not something I'm *terribly* concerned with, but.. It's also a solvent, so will cause chemical stresses as well. Not knowing how much stress the existing parts have been through, all I can say is be careful. I don't know the brand/type of acrylic it is, if the overflow was heat bent or glued, etc., so just be careful with it. If it gets too hot, you can slow the reaction by using 25:1 or 30:1 ratio rather than the listed 20:1 ratio. I'd probably go 25:1 on the first batch and see how it goes. Don't worry about a fan except to blow away the vapors.
The monomer:catalyst ratio determines how "hot" it is both thermally, and reactively. a 10:1 ratio is very hot and has a very short pot life, wider ratios will be cooler and longer pot life, but you really don't want to go above 30:1 or so - it still has to catalyze and work. You will need to work relatively quickly, you'll have 5-10 minutes max on the pot life so have everything prepared and at the ready prior to mixing anything. Mix it up in a poly tub of some sort - old margarine tubs or similar work great. If you've got a few of them around - all the better. I'd probably opt for a narrower tub, at least something that will fit inside the overflow with some room to maneuver. I'm guessing you'll want to pour directly from the tub to the application surface. When you mix it, you will see tons of bubbles, don't worry about it, almost all of them will float out when you apply it.
Cover the fittings with Scotch tape to make sure you don't get any inside the fittings. Don't spill the stuff on anything. If you do, whatever it touches is essential toast. Peel the tape immediately when your done in that area otherwise that tape will never come out. Reason I mention Scotch tape rather than anything else is simply that the stuff doesn't stick to Scotch tape very will as compared to other varieties.
Sanding the PVC and acrylic is not beneficial IME. It won't hurt anything, but never helps either (even with silicone FWIW.) The only prep work to do is to blow out any particulate matter with compressed air and then wipe the PVC and acrylic with denatured alcohol (shellac thinner)
Once applied, the 40 will start to skin within minutes and will be hardened enough to move within a few hours. 24 hours later, should be good to go.
FWIW, it's not that big a deal to work with, in fact it's pretty easy, but also easy to screw up if not real careful.
Good luck with it :beer:
Can't wait to see how this turns out. Good luck!
