Wednesday, December 29, 2010
Mold Making Tutorial
Mold Making Tutorial by Donn Kinney of Bishonen House.
All the links I have ever found for this tutorial have been broken, for example:
> A Resin Casting How-To
> Bishonen House Mold Making Tutorial
> Donn shows you how he makes his molds.
This information was saved by a member of The Joint, and recently made available. It seems to have come from Archive.Org.
I am posting this tutorial for educational purposes, and because it is difficult to find, otherwise. I do not guarantee that this information is currently useful or correct.
I have edited the tutorial to correct typos, misspellings, and so forth. The tutorial begins here:
Making a basic silicone mold with a core.
Please excuse typos/misspellings/rants etc.
This is far from a polished page, but as I've been promising about 2 dozen people a tutorial on how to mold hollow parts I decided that I really needed to get this page up. (I'm sorry it's not more complete.)
Here we start with a finished proto body sculpt. (Getting to this point is a whole other tutorial, we'll skip that one for now.)
The first stage to making a production mold is dividing off your sculpture into sections. Usually body parts can be divided off into a 2-part mold with a front and a back.
I built up a wall out of WED clay (a water based, slow-drying clay).
Most water-based pottery clays will also work.
(Remember when molding with silicone always do a small sample experiment first to determine if the material you're using contains sulfur.)
Notice how I add acrylic hemispheres, and a channel wall, to the clay dividing wall?
These will make sure that both halves of the finished mold line up perfectly.
This would also be a good time to point out the built-up column at the base of the body.
This will be the area that the core mold forms into and attaches to (you'll see later).
After the clay wall is built up, and a perfect clean dividing line is created where the waterclay meets the chest sculpt, build up a cardboard wall around the edge, using hot glue. (This will hold in the silicone, so make sure it's completely sealed and strong.)
You do not want $100 dollars worth of silicone to end up on the floor and your master sculpt ruined!
Once you're sure you've created a sealed mold wall, mix up and pour in the silicone.
For my master molds I use MoldMax30 silicone from smoothon.com
Please note if you do not have a vacuum chamber to degass your mixed silicone
you will not be able to get bubble free molds using the high strength pro silicones.
(Using vacuum chambers is enough info for another tutorial.)
MISSING 2 PICS
The next step is to wait 24 hours for the silicone to set up.
Once the silicone is set up, flip over the mold and take the bottom piece of cardboard off.
Be carefull not to tear the cardboard on the sides! You still need that.
Now carefully dig out the waterclay, (you don't want to scratch your master sculpt) except for the thick column under the body.
We want to leave this because it will be the channel for a our core mold.
Once all the waterclay is removed, use a litle water on a stiff brush to get every bit of the water clay off of your sculpt and the part of the silicone that is exposed.
Once your model and the mold are all cleaned, coat the exposed silicone thoroughly with
a release agent.
This is very important!!! Remember, silicone will only stick to one thing, and that's silicone!
Once the exposed silicone is coated with release agent, then mix up more silicone and pour the other half of your mold.
After waiting another 24 hours, peel off the cardboard and gently pry apart your finished front and back body mold. Once you pull out your sculpt and put it someplace safe it's a good idea to put the mold back together (always store your molds closed) and let it sit for 4 or 5 days so that it fully cures.
If you're in a hurry you can bake it at 100 degrees Fahrenheit for 5 or 6 hours.
After the mold is fully cured take it apart and begin to build up waterclay where you want your resin to build up.
My bodies are hollow in the midsection so I'll leave a nice hollowed out area there, ..(do this to both sides of the mold)
NOTE: There's no clay in the upper body in this pic but that's because the hollow area is going to be sealed, so that when i pour the core from the bottom, no silicone will flow into it.
Once you have both sides of your mold built up with clay, where you want your resin to be, fit them back together (this may take a while). Shave down and build up clay so that they fit together perfectly again. Once you have them together, use a tool or you fingers to smooth the halves of the clay buildups together so that when you pour in the silicone for the core it won't leak into your mold.
(This would be realllly bad!)
Build up a cardboard wall around the bottom of your mold.
You can hotglue cardboard to silicone, it won't stick permanantly.
If you don't fiddle with it, it will hold and be leakproof just long enough for your silicone to cure.
Coat the exposed silicone with release agent
Then pour in your silicone and wait 24 hours
Once your silicone has cured, gently tear off all the cardboard (The small hole in the mold was made later so that resin could be pored into it.)
(Making pour holes/vents is yet another tutorial.)
Now take apart your mold and wash all the water clay out and dry your mold thoroughly.
You now have a 3 piece mold; the 2 sides, and a rather lewd looking core that keeps
the lower half of your casting hollow.
Here's a look at a prototype head mold and its core.
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported License.