Re: Wax Shrinkage


Bramblebush ForumsFAQ

Posted by Jesse Brennan on April 08, 19100 at 17:17:37:

In Reply to: Wax Shrinkage posted by PhilB on April 07, 19100 at 12:15:57:

First thing go further down on this forum and check out casting wax and investment casting. Also where are you

located? How big are the objects you are casting and with what process. open molds- closed molds ?? How much

wax are you using? The more information you post the more help you can get. See:

"candle wax" is probably mostly or all paraffin wax which is a terrible molding wax . It is a perfect straight chain

hydrocarbon with no side branching. The molecules slide on each other like rubbing the back sides of two pieces


sand paper together.

Add some side branching and it is like rubbing the sandy sides together. Paraffin is cheap. Bees wax is added or

used for some candles but it is soft and very sticky and more expensive.

Sculpting wax today will use a microcrystylene wax as a base. This is also a petroleum by product along with

paraffin but has been refined to produce other properties.

Industrial investment casting wax pattern are produced in metal molds in a process similar or identical to

pressurized plastic injection molding. Waxes are hard and will contain some polyethylene and maybe some


The specialty waxes for small jewelry sized objects are produced in rubber molds with a pressurized wax feed.

Bruce's waxes with rosin will make a stiffer wax but it will may be sticky. I make up witches brews that include

polyethylene to stiffen up some batches. The wax is 100% consumed so I don't worry much about a recipe I add

something to get what I want.

Firm for a non sagging base material softer and sometimes a little sticky for modeling. Bruce does a lot of large

professional sculptures - I do smaller stuff with about 6 pounds of wax consumed at a time. I am a retired

engineer and know a little about what is going on but I don't have problems with what I am doing so I leave it that


Casting wax in molds is no different than metal casting - the part and molding process has to be designed to control

material shrinkage .


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