Smooth-On Mold Max 30

[crazyjim]

Has anyone used this stuff? Do you really need to use a gram scale to weigh it?

[Lownslow]

nah its 50/50 i love it its a big step up from the oomoo sticks to every part stuff.

make sure when you make 2 part molds that you have enough to cover the one part completely i noticed this stuff doesnt adhere well to itself after its dry which is great for 2 part molds

[Chief Joseph]

Mold Max 30 is a tin-cured silicone that is mixed 10:1 with its catalyst, so you should use a gram scale to get the proper ratio. It's very forgiving, though, and you can be off a little and still be okay. If it's under-catalyzed by a few percent, then it will take longer to harden. Has to be post-cured or the first casting or two will be ######. Shrinks a bit over time, so it's best to burn the mold out with castings soon after it's made and toss it. Can't pressure cast with it unless it was pressure-cured or vacuumed.

The new Mold Star 30 is a platinum 1:1 mix that is a pure joy to work with. Costs quite a bit more than the tin silicone, but the speed and thin viscosity is great. It can be measured by volume or weight. No post-cure needed since there's no alcohol in the rubber. Actually shrinks just a tiny bit, which is unusual for platinum, but not nearly as bad as tin-cured rubber.

[crazyjim]

Joseph - I don't know what you mean by "post cured" or "burned out with castings".

I got 2 gallons of the Mold Max 30 (A& for free. I guess I need to get a gram scale.

[Chief Joseph]

Joseph - I don't know what you mean by "post cured" or "burned out with castings".

I got 2 gallons of the Mold Max 30 (A& for free. I guess I need to get a gram scale.

Post-curing is when you heat the green (fresh, new) mold for about 4 hours at 120 degrees to drive out the residual chemicals and strengthen the rubber. A burned-out mold is one that has been used up, i.e. the resin castings have burned it up so badly that it can no longer produce quality parts. A tin-cured rubber mold should be used up fairly quickly so that all the parts pulled from it are dimensionally consistent. How old is this Mold Max 30 you got for free, and has it ever been opened? This stuff goes bad fairly quickly after it has been opened, especially if the humidity is high. Maybe it was free for a reason

[crazyjim]

I'm in Florida so the humidity is high. The formerly unopened cartons were dated June 8 2009 and the other September 21, 2010. The boxes were unopened so I figure the contents were never opened.