Wednesday, June 6, 2007

Quick How To on Mold Making - May 31, 2007

As I mentioned in my intro to this website, a majority of my time will be spent actually manufacturing products from my kitchen under a makeshift hood. In the spirit of education, I want to walk you through the step-by-step process I use to make a mold. Pardon the picture quality, but my digi cam was at a friend’s house, and I had to use my phone cam.


Pick an object to make a mold of, but be careful to pick something that is relatively simple in design. For instance, a block is a lot easier to make a mold of then an action figure that is holding a sword. Objects that have many complicated angles, “limbs”, or holes in them will be hard to make molds of.

Here is the object I chose (it’s a wooden knob):


Take the object and glue it down to a piece of cardboard. I use glue that is made for sealing cracks in gutters on houses. It’s great because it works instantly, and takes very little time to dry. I think any silicon based glue would work well for this too.

After you glue the object to the piece of cardboard, you will need to build a wall around it. The wall needs to be high enough to cover at least ½” higher than the top of your object. Also, be sure also not to build walls that are farther than 1 ½” from your object either. I’ll explain later.

In the picture below, I took the wooden knobs, and glued them to the cardboard, then glued sections of PVC pipe around them to act as walls.


Once you have your object glued down, and walls surrounding it, you will need to spray a release agent into it so that when you pour the rubber, or whatever you want, into it, the mold making material doesn’t stick. I use this stuff called Universal Release Spray.


Mix up whatever mold making material you bought, and pour it into your molds.I use a product from Smooth-On called PMC 121/30.

BTW, I buy all my supplies in San Francisco from this place called Douglass and Sturgess.

Now wait! Overnight!!!!!

….and be sure to ventilate….the stuff gets smelly (see fan)


Time to get your mold!!!!!!!!!!!!!!

So you had the patience to wait long enough for your material to set overnight, and it’s ready to be released.

Gently tear your object and makeshift walls away from the cardboard. You will be left with this. Notice your object is still stuck inside the mold, and stuck inside the walls you made around it.

Thank god you sprayed the release spray. Right?!?!
Simply push the mold out of the wall you put around it, or tear the walls away.


Time to rip out the object embedded in your mold. This takes a little patience, especially since it is sealed inside the rubber.

Side Note: Oh sweet sweet rubber, how I love your stretchy properties.

In order to get your object out, you will need to push it out of the mold. Depending on what type of object you have in there, you might be able to simply push it out, but because my knob is mushroom shaped, I will have to cut it out.

In order to cut it our, simply cut from the base of the object, where it was glued to the cardboard, and slice through the rubber in an “S” pattern (as not to cause more tearing than necessary in the long run). DO NOT cut all the way to the bottom, only cut enough to get the object out.


Once the object is out, you are free to make as many molds as you want from that mold. Just remember to ALWAYS use release spray inside the negative space in the mold, otherwise whatever you pour inside will get stuck.