Friday, September 2, 2011

Carving Wax Shrinkage?

Q: How much does Carving Wax Shrink?

The only source of information I could find on this is from kwm at Atelier de Poupee. The post states ".02777%. Almost 3% shrinkage."

Why is there such limited information? Different combinations of ingredients are going to have different results.

The recipe I followed for my Carving Wax:

4.5 parts microcrystalline wax
4.5 parts paraffin wax
9 parts talc
1 part beeswax
1 part carnauba wax

The recipe for kwm's Carving Wax:

1 part paraffin
1 part microcrystalline wax
2 parts talc

Notice that we also have a slight different in the recipe for the carving wax. Basically, kwm omitted the use of beeswax and carnauba wax. How will that affect the difference in shrinkage?

So how do I test carving wax shrinkage? I am going to make a plaster mold of a tile that has a 5cm line that can be measured.



How reliable will that information be?  Just measuring one carving wax cast isn't going to be enough.  Although I could probably get more accurate numbers casting and measuring 100 times, I am not about to do that.  So I will just settle for casting 5 times and getting an average number.  Things like the heat of the mold, the heat of the wax, etc may all factor in to the calculation of shrinkage.  I will try to take in as many factors as possible, but there is a limit to how much I will test.  I am just trying to get a general number for shrinkage and not one for scientific application.

Why is knowing shrinkage important?  Lets suppose you first make a plaster mold of your original sculpture.  Then you cast with carving wax.  Then maybe after some work on that carving wax copy you make a junk moulage mold.  You cast another carving wax copy from that mold and work on it some more.  Maybe even after all that you want to make another junk moulage mold and cast in carving wax again.  Maybe you repeat that a few times.  Depending on carving wax's shrinkage, your original sculpt is getting smaller every time you make a new mold and cast it in carving wax.  This may not be a big deal if the size of the final copy does not matter.

Something else that needs to be factored is the mold's shrinkage.  Plaster mold has no shrinkage, but what about junk moulage molds?  It is recommended to use a moulage mold as soon as it is set and not to just store it for later use, but why?  Because of shrinkage.  So what kind of shrinkage are we talking about?  If I stored a moulage mold in an air tight container for a day, how much shrinkage are we talking about?  What if I stored it for a week?

So many questions that I want to find some basic answers for.

So what am I going to test for?

Plaster Mold
Test room temperature and warmed up plaster mold.  Test pouring 145 and 160 degree carving wax.  Cast 5 times per scenario.

Moulage Mold
Test room temperature mold.  Test pouring 145 and 160 degree carving wax.  Test using moulage mold immediately, 24 hours later, and x days later.  Cast 5 times per scenario.

Sounds like a lot of fun.

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