Brush-on latex glove mold is dehydrating Hydrostone?

[helix_3]

I bought some latex Alumilite Mold Builder and brushed it over a small test sculpt made of oil clay.

After letting the mold cure for multiple days I tried casting in Hydrostone. The HS cured perfectly hard and smooth in the plastic mixing cup, but had a dehydrated, chalky finish wherever it was in contact with the latex. This outer layer could be easily removed with a fingernail, and was maybe 1/16" deep.

I thought maybe the rubber was still porous and allowing moisture to escape, so I made another test mold and tried boiling it (supposedly that's supposed to accelerate the rubber cure process?), but that didn't fix the issue either.

Does anyone know what is going on here? My next best guess is that the rubber is too thin or I need to wait a week for full cure, but I wanted to sanity check before wasting any more time.

 

[Duncanator]

I wonder if it is some sort of chemical reaction from the latex or one of its other ingredients. I've heard that sugar can stop cement from setting, so maybe there is something leeching from the latex into the outer edges of the hydrostone.

I am curious what the cause may be. I wish I had a better answer for you.

 

[PoopaPapaPalps]

Perhaps you could try sealing the negative of the mold with something, like a clear coat, before pouring the hydrostone. I'm thinking there's something in the latex. If the problem persists, I'd recommend switching to silicone molding rubber.

 

[JNordgren42]

I concur that it's probably a reaction with the latex. It's a different process, but as an example I know most 3D printing resins will prevent platinum catalyzed silicone mold agents from curing.

 

[TazMan2000]

Alumilite doesn't play well with water.

TazMan2000

 

[mcusanelli]

You might have more luck with a urethane rubber to cast plaster in. I used it years ago and it had no ill effect on the plaster castings

 

[drusselmeyer]

Make a hydrostone or concrete slip mold. That should solve your problem.

Remember to make sure there are no undercuts in the original object or you will lock the original in the mold.

If your original is too complex or has too much surface detail for a rigid mold, try making a slip mold out of oil based clay. If you keep it cold, it won't distort. You may need a mother mold for this process.

 

[rbeach84]

I concur that it's probably a reaction with the latex. It's a different process, but as an example I know most 3D printing resins will prevent platinum catalyzed silicone mold agents from curing.

The Smooth-On website states that the inhibition factor is with 'UV cured resins that are not fully cured'. Guess the trick is to make sure resin parts get fully 'lit up'...?
Regards, Robert