Urethane resins are inconsistent - epoxy resin is more reliable, but requires patience

I was in a rush to see my new mold the other day, so I purchased some urethane resin, smooth-on 326, with a medium strength and 5-10 minute pot life. I had surprisingly good results and started retooling my setup to run with the 326. I used up my 2 pint kit and on a Saturday afternoon I visited my local supplier of all things molded, Douglas and Sturgess, but they were out of the affordable pint kits. I was in the framework that urethane was now working for me and went ahead and tried the Task 9 Urethane resin by Smooth-On as a replacement. The results were not the same and I was left feeling like I wasted an entire day. It may be the moisture, which the sales agent at Douglas and Sturgess warned me about, or it may be incompatible with the pigments I am using, like aluminum bronzing pigments and steel powder. The results were more bubbles than ever, with pits and holes, and when I submerged the pieces in water to clean off the mold release, they curled and buckled to the point that they were not useful.

The good news was that I got a workable batch out with the Smooth on 326 and would use that again in a hurry, but I switched back to epoxy for a final run. Patience is all that it ask for and now that I used my mold once and no what to expect, I realized I don't need to be in such a hurry. Going back to the epoxy did have some risk in that a mold with the urethane could react differently and stick to the epoxy or break down the mold, but it didn't and a new batch of emblems made with epoxy emerged the next day. The firmness and the rigidity of the epoxy is superior to the urethane and the consistency of the epoxy makes it worth the wait.

The information that I gained from this weekend is that urethane can be used, like epoxy, but the Smooth On 326 is better than the other urethane resins for imitating epoxy resin with powder pigments. Also, I can go back and forth with my molds using urethane plastic when I am in a hurry, but the slower setting epoxy is a more detailed and better final product.