One of the bummers on working with plaster to mold stuff is that it breaks, either if you’ve dropped it, or put a weird pressure on it, or even by simply demolding it.
Step 1: Burlap
You can use burlap in between layers to add strength to it.
Step 2: Mixing the Plaster Like a PRO
You can mix the plaster properly by adding water FIRST, and dust the plaster on top UNTIL all water is absorbed and it ends up looking like a dry soil, then mix it throughly to use.
Step 3: Prepping for Mold
You can avoid cut areas that would lock a mold.
Step 4: Intensify Plaster's Curing Process
You can spray some water after the mold starts to cure, then cover with a plastic, so the reaction of the plaster will "kick in" stronger, and the mold ends up firmer (Rob Freitas tips).
But sometimes, your mold just breaks! And that sucks!
Step 5: Products & Tools
The misshapen can be fixed by mixing some more of your plaster, and just patching the holes. However, as I do work the minimum as I possible can with plaster, hence I hate the mess it makes, I’ve come up with a fairly obvious solution: using a paste that is close in chemicals of your plaster to patch those holes.
Since I use plaster of paris or stone in most of my molds (mainly because this is what I can find on the country I live), the paste that would best work together is Spackling Paste, which is made to fill holes in walls, and stuff like that.
So basically what you'll need:
• Spackling paste;
• Clean Spatulas; and
• Broken Mold.
In this video you can see exactly how simple it is to fix a mold with it. And mind you, my mold was in a dreadful state.
Per usual, I do let my molds dry for 24 hours so any water on the mold can evaporate. You don’t necessarily need to do this, but I do see a difference on the casting of the products when I wait.
Another alternative to spackling paste is: Acryl 60 mixed with the plaster of choice (it works with ultracal, so I guess it works with others).
I hope you found this post useful. Let me know if you do break your molds as often as I do, and how to you usually fix them!
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