Enduro Soft - 2 Part Liquid Polyurethane Casting Rubber - Durable, Rubber Casting Resin - Soft Rubber Feel (2 lb kit (32 oz kit))

I am a complete beginner at urethane molding. I needed to mold some underwater cable splices which have to be absolutely waterproof. This seemed like the stuff to use. It worked great! See the results in the attached pictures.I made a mold out of High Density Polyethylene (HDPE). Pictures of the mold are attached as well. I did some reading and followed the directions. It is important to mix well, and avoid all moisture or moisture bearing materials (like wood). The coloring was done with mica powder (only a small amount needed). The Mica flakes are what gives the urethane its mottled appearanceThe result was waterproof, tough, and flexible. I just bought some more of this stuff for another project. It is easy to use - just mix (thoroughly) and pour in one mold hole until it wells up in the other. In the picture the gray one has just come out of the mold and hasn't been trimmed yet.For HPDE you don't need any mold release spray. I had added jack screws in the mold to force the clamshells apart, but this was overkill. The mold comes apart easily. I did notice that the urethane sticks tenaciously to polystyrene. All the polyethylenes should work well for solid molds.

I found it excellent for “potting” electrical components! Mix very well. When you’re done mixing, mix some more! The walls of your mixing container may have spots that aren’t mixed so don’t mix in the form or mold. Pour into the final product. The number one reason people have problems is not enough mixing! Works amazingly well for potting LiFePO4 batteries for high vibration applications.

Sets up faster than I'd like, but works well enough if you follow instructions exactly. Did not work at all the first few tries because I added a drop of dye and that ruined the whole batch. Do not add dye.Casts in an amber clear and has a smooth, eraser-like texture but seems to hold up well.

I expected this to be more flexible. It is very rigid and not for making molds.

After reviewing available information as to what molding compound I should use for my project, I settled on polyurethane because I needed a durable material to cast many plaster parts for an indoor "water feature." (Don't ask.) Anyway, everything was fine until I tried to remove the positive master from the urethane. It was murder even thougn I slathered the epoxy coated mold in silicone plumbers grease AND silicone spray. The master was destroyed but at least the urethane mold survived, only because urethane is such a resilient material. Before I would use this again, I would have to find a better mold release, if there is such a thing.

You have a 5 minute working time with this stuff at room temperature, I used a cordless drill with a paddle in it as my mixer, do this for at LEAST 45 seconds. Start your drill submerged and keep it submerged for the duration of the mix, and you won't get any bubbles in this stuff. Mica powders are compatible and produce striking colors in the resulting part.Your results if you follow instructions above is a mindbogglingly strong casting after about two hours. I have yet to see a soft urethane this strong.

Easy to mix and use

This stuff is advertised as having a 7 minute work time, but I find by the time I've mixed and degassed, which is usually around the 3 minute mark, the resin is too viscous to poor into my molds. I contacted simple resin support to see if there was any way to extend the work time and their response was I should buy another one of their resins. So basically to use this stuff I just have to skip degassing which means I end up with all kinds of bubbles in my cast parts.I'll be looking for another source of polyurethane rubber in the future.