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Problem with Mold Making

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I have been pouring my rocks for quite a while, but the last two times I tried to mix the powder and water it turned to cement before I can get it all mixed up.  I've never had this issue and I've tried two different brands now.  What could I be doing wrong?  Suggestions of a product to use?  This second time which was a failure I was using ultracal 30.

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Hello Garden Rock.

Welcome to the Forum. What are you trying to do? Clay pieces, cement pieces? 

Ultracal 30 is a USG product. The bags have a "packaged date" on them. What is it on yours? 

It sounds like you may have old cement. Anything over a year old is poor quality. 6-12 months will be problematic. Under 6 months your mixing method may need to change.

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Thank you for the welcome!  I pour the mix into silicone molds to make different shapes of rocks which I paint with intricate pet paws, cats, yin and yang, tree of life, etc. I looked at the plastic bag and there is not label or date on it and I already threw away the box, etc. I have ordered some gypsum cement.  Hopefully that will work better.  I've poured so many rocks and never had this issue before.  Thanks for the suggestions!



Edited by Garden Rock Art
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Both USG (Untied States Gypsum) and GP (Georgia Pacific) sell their products in 50lbs paper bags. If your plaster was in a plastic bag, in a cardboard box, it means your supplier is repackaging the plaster. This prevents you from knowing hold old your plaster is. (All 50lbs bags are dated with the factory "packing" date.)

If it's not too much to bear I would suggest you buy a 50lbs bag. That way you will know how old your plaster is and you can learn about the effect of age on plaster. 

The fact that your plaster mixed quickly means it is old or it has been exposed to moisture at some point. If you buy your plaster in 50lbs bags you can better control how the plaster is stored.  




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