Is smooth-om oomoo 25 a good rubber?


Well-Known Member
Hi All -

I am going to have to make my first 2 part mold soon and in my research, it seems like the oomoo brand is pretty good for beginners -

Questions - is oomoo 25 or 30 better for a first time? Is there a detail hold difference?

Also, do I need a special release spray?

Thanks guys! PS - This is a mold of a personal sculpt that I did...
I buy oomoo by the gallon hehe. It's great for beginners since there is no degassing needed and you don't need a scale to measure it out. Its big drawback is its limited lifespan, meaning you can only pull so many castings from it before you'll need a new mold.

I believe the only difference between 25 and 30 is the cure time. Oomoo 25 cures in about an hour and a quarter and I think 30 cures in six hours. Oh yeah, they're also different colors ;)

They both capture amazing detail. I've found my fingerprints in clay models visible on castings because the mold caught them! Using a mold release will help your mold last longer but I don't think it's strictly necessary with oomoo.
I'll echo what Steamtech said. It's easy to work with with the self-degassing and 1:1 ratio but the molds die fairly quickly and don't have a huge shelf life. Good to start out with but if you do a lot of casting you'll move on to better quickly.
oomoo is great for beginners...

depending on what your casting you may not need a release spray....say with clay, taking out the clay and cleaning out the mold is fairly easy..

but let us know what your casting, you'll get more tips..

when the shop i did work for back in the days. we would spray a release agent in the mold and powder it with baby powder, shaking out the excess baby powder when doing a castings.
MoldStar is a better option if you can go for the little higher price. It's a platinum cure so it will last far longer and shrink less.
I don't know if a platinum silicone like Moldstar would be a good idea for a beginner. It's got such a long list of things that will inhibit curing that I don't think it would be a good risk.

Besides, if he's anything like the rest of us, he won't have much need to hold onto his first molds. No one is ever very good at it at first.
Thanks everyone - Sounds like its exactly what I need - This is an original sculpt for a client, but I need to present the sculpt AND a paint master, so it would really be a one-time-use mold... Sounds perfect!

The original is going to be primered when I cast it - Will primer need a release? I would assume so..
Mold release certainly won't hurt and should help you make sure nothing gets left behind when you demold.

A little trick I use around here is to keep some expanding soft foam (casting foam, not the insulating stuff) and pour the first cast with the foam. It's cheap and you don't need much, but it will pick up any stray bits of clay or primer left in your mold and leave it clean for your real casting.
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