I just took a class this weekend on resins. I learned that Urethane resins are really hard and you can mix them up and use them for lathe work or saw them without them "gumming" up. However, if you use them with wood you need to make sure the wood has zero mosture in the wood (use a moisture meter), because they will foam up and make a mess. Epoxy resin doesn't do that so as a background, etc they will work no matter the moisture content for the most part. Also adding liquid dye vs powder dye can be an issue. Liquid dye does add more liquid to the 2 part combo so it may slow the drying process, powder dye does not have that problem. And they showed us ways to reduce the bubbles as well... interesting class, quite fun... I too am going to give it a try now that I kind of know how it works.