I’ve been mixing epoxy in the little plastic medicine cups using “craft sticks” (think Popsicle stick). I thought I was doing a pretty good job of stirring, spending some time scraping the sides and swiping along the bottom corners of the cup to ensure everything was mixed up.
Last night I mixed up about 2 cc of epoxy, mostly just to try out my new syringe dispensers. I let it sit in the cup with the stick propped up in the center. Today I popped the slug of glue out of the cup. Lo and behold, there are sticky spots around the edge! Nearly all of the glue is perfectly hard and cured, but there is just a tiny little bit of uncured epoxy right around the bottom edge. Apparently the stir stick is not a good tool for making sure ALL of the material gets mixed together.
In light of that discovery, today I did another 2 cc sample. This time I did the mixing with an acid brush with the bristles trimmed down to about 1/4″ to 3/8″. After mixing I cleaned the brush out with a little MEK, just to see if that would be worth doing or not. We’ll see how that one turns out after the epoxy has had a chance to cure. Acid brushes are pretty cheap, so even if the MEK cleanup doesn’t work out it’s not a big deal. You can buy the brushes by the gross for around $0.12 to $0.15 each. But what will I do with about 950 craft sticks? Good thing I have grandkids.