[Geekie1]

Hammer,

The biggest problem with using epoxy is metering the correct proportions of resin and hardener, insufficient mixing and ambient air temperature. The pumps are OK, however you can't always count on them to meter the resin and hardener in exactly the correct proportions. Sometimes they burp because of an air bubble or pump defect causing a mismix. I use two 8 oz transparent plastic cups one inside the other to pump into. The outer cup I mark the correct levels of resin and hardener proportions, (2 parts or pumps of resin to 1 part or pump of hardener, or 3 parts or pumps of resin to 1 part or pump of hardener,) or whatever proportions the brand of epoxy calls for with a "Sharpie" pen. I mix small batches of resin & hardener in the inner cup using the marks on the outer cup to measure to. I use the pumps but if they deliver the wrong amounts, the mistake is immediately apparent. It doesn't happen often, but when it does I throw away the bad batches and don't try to correct by guessing.

Sufficient mixing of the resin and hardener should take about 2 minutes with a wooden stirrer and you should scrape down the mixture on the inside of the cup while mixing. The resin mixture will get hot in the cup. Smaller batches will get less hot than big batches. If you use a large styrofoam cup to mix, the cup will probably melt so use smaller clear plastic cups, not styrofoam. If it gets too hot, pour the mixture into a flat shallow plastic pan to slow down the curing. If it is really a hot day, (85 degrees and up) the mixture will probably get very hot. If the air temperature is below 70 degrees, the epoxy will be slower in kicking. When the epoxy has been mixed sufficiently, you can then mix in the cabosil, microballoons, or even sawdust to thicken the epoxy to about the consistency of creamy peanut butter. I throw away the inner mixing cup with each batch because if you mix a new batch in the previous cup the proportions will be off because of residual mix left behind. You may end up with epoxy that takes weeks to harden or hardens too quickly which will weaken the cured epoxy. The flat plastic pan I use is a smaller paint roller pan plastic insert. When the epoxy hardens the pan should be flexible enough to pop out the cured epoxy so you can use it again.

I hope this helps!!

Ed G.