Welcome to the world of mold making and casting! This class will teach you the ins and outs of how to make easy molds, enabling you to cast unlimited reproductions of almost any object in a variety of materials.
You will finish with a solid understanding of fundamental techniques that will empower you to tackle new and exciting mold making projects moving forward!
Here's a list of tools that you'll need to get started on your path to becoming a mold making and casting pro! Purchase links have been provided both here and *in the detailed descriptions that follow -- below the lists, I'll go over each item individually and explain their function in the mold making and casting process.
The materials used for mold making and casting vary from safe to not so safe. Even when using materials from the least harmful end of the spectrum, it is always best practice to be as cautious as possible when working with any mold making and casting material.
Things you'll need to ensure your safe return from any mold making adventure:
*Only necessary when working with powdered materials.
**Recommended when working with resins, polyurethanes, etc.. All material's packaging and safety data sheet (SDS) will tell you whether or not a respirator is required.
Try not to work in your kitchen. If you must, COMPLETELY cover your work areas in a few layers of butcher paper or newspaper and definitely never use containers and utensils you use for food to mix or stir any mold making or casting material. (If you're mixing soap or chocolate for casting, that's an exception to the rule!)
A mold board is a piece of rigid and perfectly flat material that you make your mold on. Building the mold on a separate (and smaller) work surface allows you to:
The materials I recommend using for mold boards are:
*Do not use hardboard for plaster molds.
The reason you want to build your molds on a rigid surface is that if you used a flexible plastic for instance, like a roll up cutting board, there is more of a chance of a portion lifting up, resulting in a break in the seal and the mold material spilling out.
I keep a variety of sizes on hand, but I find the two most useful sizes are 14" x 14" and 10" x 14". The rule of thumb for size is that you want the build board to be at least 2-3" bigger all the way around than your mold walls. This gives you plenty of room to add sealing material AND catch the flow of any runaway mold material if something goes wrong.
Mold retaining walls, also known as 'forms' or 'boxes', are used to create the support structure that the mold material is poured into.
I like to make my own mold boxes and retaining walls, as opposed to using old food containers or the like, because I can better customize how the box/walls fit around the model. The better and more customized the fit, the less mold material you'll need to use, which means substantial savings!
There are four different kinds of retaining wall materials I like to use to create custom mold forms/boxes:
All but the corrugated sheet plastic are re-usable.
Corrugated Sheet Plastic
The corrugated plastic is the most customizable of all the wall materials. You can easily cut it to the height you need (1/2" higher than the model PLUS at least another 1/2" to prevent any overflow) and by cutting halfway through the material (cutting one side only) you create a hinge, allowing you to make simple shape walls/forms (like pictured above) or complex ones.
Cutting alternate sides lets you bend the material in both directions to follow a model's contour.
This rigid material is best used for making smaller molds that are square or rectangular. It comes in all sorts of colors, but I choose clear because being able to see what is happing behind the walls is mondo helpful.
You can cut the walls to size yourself from a larger sheet that is 3/16" or 1/4" thick (using this tool and a straight edge) or have your local plastics shop cut to size.
Styrene or Clear Polycarbonate Sheets
These flexible and tough sheets are so incredibly handy for making cylindrical molds for round or roundish models! You can easily cut it to the height you need (1/2" higher than the model PLUS at least another 1/2" to prevent any overflow) and roll it up to the exact diameter you need!
The strongest cylinder shape is created by making sure that the sheet goes around slightly more than twice so that the wall is two layers thick and has an overlap for taping. I show you how to make this kind of mold wall in the Flexible Block Mold lesson!
5/8" Laminate Boards
These guys were my go-to for plaster mold making for my slip cast ceramic business. They are sturdy and adjustable, which allowed me to use them over and over again for many different sized pieces. I won't be using these in this class, as the casts I'm making are all too small for their larger size. What is the saying? Don't bring a gun to a knife fight? Yes, these were just too big for this class's projects, but this style of mold wall is so useful and practical that I felt it important to share their magic with you just in case you ever need it!
Here's a quick visual tutorial on how to whip up your own set of 4 clamp-able mold walls for larger molds.
Tool & Supply List:
*If you don't have a table saw, you can have the boards cut at the hardware store for a very small fee.
Now all that's left to do is watch the little animation below to see how to set up, adjust and secure the walls!
To prevent any potentially harmful mold making or casting materials from getting on your work surface, cover all the surfaces you'll be using in several layers of kraft paper or newsprint.
I use plaster and silicone for most of my mold making, both of which dry/cure, making container clean out a snap. This is why I prefer to use plastic mixing containers with measurement marks on them. It saves me from having to weigh out my materials and wasting containers.
But if you will be mixing materials that won't be easily cleaned out, then I recommend using wax lined paper ones, as the environmental impact of disposing of these is less than the plastic.
There are more mold making techniques and materials than can be covered in a beginner class, so I chose to focus on silicone rubber due to how easy it is to work with and how versatile it is in what you can cast into it.
Having said that, I think it's important to be aware of the other options out there. The basic mold construction techniques I'm teaching here will be similar, if not exactly the same, for other materials – but be sure to read the instructions that come with each material and research mold making techniques specific to that material, to be sure you're doing it correctly and safely.
Molds can be made from the following materials:
*suitable for making molds of body parts
The world of casting materials is full of fun options! The three I use in this class: water to make ice, soap, and plaster are just a few examples of the MANY choices out there!
If you make a food-safe silicone rubber mold, you can cast:
In the same food-safe mold and any other silicone mold, you can cast:
In an unsealed plaster mold, you can cast:
In an alginate mold you can cast:
NOTE: DO NOT cast Polyurethane Rubber in an alginate mold. It will not set in such a moist mold.
The hot glue gun definitely wins the award for the most versatile tool in the making/crafting world. For our purposes, we'll use it to secure models and mold walls to mold boards.
This is an invaluable member of your mold making tool team! This oil based clay is sulphur-free so that it won't interfere with the curing process of platinum based silicone rubbers (yes, that's a thing) and it never dries, so you can walk away from your project and come back with no worries that you'll have to start again due to dry, cracked clay! I use it to:
It's seriously useful stuff!
Disposable stir sticks are necessary for all material mixing, no matter the kind. Keep a supply of (L TO R):
Different amounts and types of mold and casting material will require different shapes and sizes sticks!
Masking tape is just generally useful, but specifically awesome at securing both the corrugated plastic and flexible sheet plastic mold walls.
These are used to hold together two or multiple part molds. I use heavy duty rubber bands for smaller molds and Universal webbing straps (on the right) for larger ones.
My scraper is a little long in the tooth and is probably due for a shiny new replacement, but whether new or old, this tool is super helpful in removing both cured molds and hot glue from the mold boards and walls. This allows you to keep using them both over and over again.
These are necessary to cut the flexible mold walls down to size, cut mold walls free of their hot glue seal, and cut models out of flexible block molds.
These are my two favorite tools from an inexpensive kit of sculpting tools. The sharp point with a flat edge guy on the left is a whiz at cleaning up edges when making a two part mold and the round end of the one on the right is perfect for creating keys for two part molds (I explain what keys are in the lesson on two part molds).
These office helpers are very useful in this world too! They will get used to measure and mark mold wall locations, mark mold material depth on mold walls, and calculate/keep track of model and mold volumes.
This kitchen staple is invaluable in keeping mold making and casting materials off of surfaces and hands. Even though both should be covered already, it's important to make it easy to keep your work area clean and drip free. Paper towels will generously help you with that!!
Sometimes it's necessary to add a mold release to a model before pouring on the mold material – or to the first half of a mold when making a two part mold so the two halves don't stick together.
These small friends are used to brush away bubbles that can sometimes form on models when using cooking oil spray as a mold release and to add thin layers of mold material to highly detailed areas of a model to ensure total coverage before pouring the mold.
This one is VERY important!! Keeping mold and casting materials off your hands is a safety imperative and these inexpensive gloves are the best way to do it. Make sure to buy LATEX FREE gloves. The curing process of some silicone mold material is adversely affected when put in contact with latex.
NOTE: Buy the correct size for your hands!
To protect your eyes from any errant splashes or flinging drips of potentially irritating materials, please always wear safety glasses with side shields. I don't know about you, but I use my eyes a lot (almost daily) and this is a very small expense/hassle for safeguarding their awesomeness.
These are only necessary if the material you're working with requires them. I always wear a dust mask when working with powdered materials and I know folks who do a lot of silicone, resin and urethane work who ALWAYS wear a respirator with the proper NOSH filters – and sometimes also work in a ventilated spray booth.
Always use your best judgement. Read and follow the safety guidelines of each material you choose to work with. Your health is worth the extra bit of effort!
Wearing an apron or other protective clothing is another way to keep yourself safe (and protect your favorite shirt). Make sure it's made of a washable material and try not to wipe your hands on it if they have any non-organic material on them. Use paper towels for that instead. Your apron is just a backup plan!
Now that you have a good understanding of how and why the tools this process needs are used, it's time to learn about the foundational concepts of mold making and casting! Onwards ho!
Share a photo of your finished project with the class!
Nice work! You've completed the class project