Everything... and Nothing You Wanted to Know About Making a Mold 101

One Part Molds

Single Mold

Group Molds

Hello Micro Fans, Micro Doc here. Welcome to this ever so confused and lengthy explanation on the brain surgery... Umm wrong topic you say... I'm supposed to be talking about Making Molds? Well okay, I can talk about that too I guess. First off, here are some materials you may want to pick up for this project.

  • Containers of various sizes
  • Small wooden dowel. I usually use around about a quarter of an inch dowel
  • Hot Glue gun and glue sticks
  • Parts you want to make reproductions of
  • Exacto Knife
  • Several Liquid Measuring Cups
  • A Rubber Scrapper

I use products made by the Smooth-On Company. The largest reason I use these products is because they offer the simplicity of adding equal parts of A to Equal parts of B. It gets to be too much of a headache to measure out amounts based on a 1:8 or some other ratio .Smooth-On offers a wide range of products. If this is your first time casting and you have never ordered from Smooth-On, then you may want to take a look at their trial kits. However, once you buy a kit from them, you will have to find a distributor to purchase further materials from. I don't know why they just don't sell it themselves.

Where can you get casting and molding supplies from then? If you just want small supplies, then I recommend you go to Micro Mark (http://www.micromark.com) This online company gets it's casting and molding supplies from Smooth-On. The products have different names, but they are still the same. If you would like to order larger quantities of materials, you need to contact a distributors. Smooth-On has a list of distributors on their website. I use the following distributor

Eager Plastics 3350 West 48th Place Chicago, IL 60632 (773) 927-3484 http://www.eagerplastics.com

For this Demonstration, I'll be using the following molding materials from Smooth-On

  1. PMC 121/30 WET
  2. The equivalent from MicroMark is Liquid Silicone Rubber for Making Molds #82083
  3. Universal Mold Release (A release agent)

 

First you need to choose what item or items you would like to mold. Now this tutorial is going to cover how to make a one-part mold. Here are some points about the one part mold

  • One Part molds work best with a small object
  • The more solid the object the better
  • Open items such as the casket pieces are difficult to mold, but can be molded using the one part mold system.

 

Now we need to find an appropriate sized container to hold the object we are going to mold. For small items, a real simple container is a film canister. Film canisters can be picked up for free at most photo development places. Most of the time these places are more then happy to get rid of canisters. It saves them the trouble of having to dispose of the canisters at the local recycling facility. Here we see that I have chosen a few parts that might fit in the containers. When you choose a container, you must have ample room in the container for the mold material to entirely cover the part. That means that you must have space between the part and the container.

Here you see single mold containers. These film canisters will hold one item.

Now that we have picked out the parts we wanted to mold, we need to set them in the container to determine if the parts will have ample room. I think I'll just take a nap for a moment.

WHAT? no time for a nap, okay then.

This is a group mold. What is the reason for a group mold you ask. Well, lets say you want to make several parts for one figure. However, you don't want separate molds for each individual part. If you make a group mold, you can keep track of where all your molds are for that particular item.

The downfall though of group molds is that you use up a lot of excess mold material. This can get costly as you may need to replenish you mold material supply because you are using it up.

Now You need to take your knife and dowel and cut yourself some small segments. I usually try to keep my segments under a quarter inch in length. However, larger parts will need larger lengths. The reason for this is that the wooden dowel segments are going to be used for our sprues or tree structure. The sprues serve several purposes.

  • The sprues will hold the part away from the edges and bottom of the container
  • When the sprues are removed from the mold, you have holes for the air bubbles to pass through
  • When the sprues are removed from the mold, you have a hole to pour your material in.
Next you need to take your hot glue gun and add a small amount of glue to one end of the dowel. Now attach it to the part that you are going to cast. There is a pattern to my madness of attaching sprues. I always try to arrange my parts so that when they are molded, they are placed at an angle. This will allow the air bubbles later in the resin a direction to escape. I usually try to place my shortest sprues to the top of the part where the resin will be poured through.

Here you can see how I place my parts in a container. I angle the part. I place my shortest sprue at the top so the air bubbles can escape quickly. I then place another dowel or additional dowels to allow holes to pour in, or additional holes for air to escape
Now once you have the dowel hot glued onto your part, you need to hot glue the dowel to the container. Make sure you have plenty of room between your parts and the container walls. If you part touches any of these, resin will leak out of that area when you start casting parts.

Here is a close-up of two single mold containers waiting for the mold material. What you see here is a wooden dowel that was attached to the bottom of the part and goes all the way back to the bottom of the container. There is a dowel at the other end of the part to allow the air to escape. The dowel that you do see will make a hole that will be used for the resin to be poured through

 

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