What is Resin?
All resins are a two part system, consisting of the base resin and the hardener (or catalyst). By themselves, they are inert compounds, but when mixed, a chemical reaction occurs where they cure and harden.
There are a few main types I’ll talk about, all with Pros & Cons.
Pot time: 10-15 Minutes
Cure time: 1-2 Hours (dependent on temperature & humidity)
Cost: $-$$ (especially cheaper if you use a polyester resin marketed for a commercial industry such as boats and vessels)
Safety: Can be dangerous. Extremely noxious smell. You must wear a respirator and work with a hood or in a well ventilated area (outside, a balcony, or in an open garage).
Pros: Cures to a very hard finish which can be sanded and buffed to achieve a shiny, clear surface. If the surface becomes scratched, that same surface can be polished once again. Pieces made from polyester can be bonded with more polyester resin to create larger pieces.
Cons: Uses drops of a catalyst liquid, which is often hard to measure correctly. Not UV light resistant, and so will yellow with time. Because it does cure very hard, polyester resin projects have a high chance of breaking if dropped or hit on a hard surface.
Best For: Larger/Thicker projects where you don’t care about it breaking, or if you can’t afford Polyurethane Resin
Pot time: 5-10 Minutes
Cure time: 30 min-4 Hours (dependent on temperature & humidity)
Cost: $$-$$$ (Epoxy gets more expensive the clearer you want your finished casting.)
Safety: Pretty safe. Just wear gloves, and have some ventilation (open windows). A respirator is not required (but be safe and use one anyways).
Pros: It’s widely available. Best all purpose resin.
Cons: Only for smaller things like gems and jewelry, as it gets too hot to cure properly in larger molds. It cannot be buffed to get a smooth finish, you must finish it with an additional layer of resin or a resin sealer spray to get a glossy finish.
Best For: Small projects like gems & jewlery.
Examples: EasyCast Epoxy Resin
Pot time: 2-10 Minutes
Cure time: 15 Minutes to an Hour
Cost: $$$ (Polyurethanes also get more expensive with an increase in clarity and for water clear versions.)
Safety: Can be dangerous. Some polyurethanes must be used with a respirator and ventilation hood. Read the safety instructions that come with your product to be sure.
Pros: Some come with a very quick cure time (under 1 hour). You can buy in large volumes. Most types are extremely strong & durable. Polyurethane is a good choice for larger projects, blades, spikes, etc. Generally comes in clear, black, & white, and is what most propmakers use for casting copies of things they’ve made.
Cons: Very moisture sensitive. May not cure well in humid climates. Some color additives do not also work well if they are not specifically designed for polyurethane resin (such as food coloring).
Best For: Large/Thick projects where you don’t want it to break, high quality products, and crystal clear gems.
Molds & Moldmaking
So you’ve picked a resin! Now I assume you’re wanting to cast something. First you need a mold of the piece you’re planning on casting to pour the resin into. That may be a premade plastic mold for resin, a silicone mold that was originally meant for baking, or even a mold you made yourself!
There are many great molds of all shapes out there for jewelry & baking, however, when purchasing a plastic mold, make sure to check that it’s resin safe or you may find that you are unable to get your resin out (often molds for chocolate have this problem). You’re pretty safe with any mold that’s made of silicone, as resin doesn’t stick to that.
What’s that? You have something that you want to cast that isn’t like any of the premade molds? It’s time to learn how to make your own mold!
Prep time: 30 Minutes-1 Hour
Cure time: Overnight
How To: Tutorial here.
Pros: Fast, cheap in comparison to other mold systems, effective when procedures are followed, these molds can be used to cast wax, plaster, plastics, concrete, and more.
Cons: Strong vinegar odor (Acetic Acid), small margin of error (it won’t work if you don’t follow directions carefully), your detail is limited in comparison to other silicone mold types. Can only be used for 1 part molds.
Best For: When you have no money but need a small – medium mold (I don’t recommend this method).
Prep time: 5 Minutes
Cure time: 2-4 Hours
How To: Silicone putty is a 2 part putty that you mix together like clay and then squish over the item you wish to make a mold of.
Pros: Fast, cheap, and easy. Moderate detail.
Cons: Can only be used to make small 1 part molds. Mold degrades quickly, and you only get 10-20 good uses out of it.
Best For: When you have some money and need a small mold. This is a good method for beginners who don’t need to make anything big.
Example: Alumilite Amazing Silicone Putty
Prep time: 5-15 Minutes
Cure time: 1-4 Hours
Pros: Is generally easy to use, keeps most if not all detail. This can be used to make 1 or 2 part molds. A great introduction to more complex mold-making methods & techniques. Good for larger & more detailed molds.
Cons: More expensive, you generally use more of it, has to be in equal parts and mixed well to properly set.
Best For: Making larger & more complicated molds, or lots of small molds in one go.
Example: Oomoo 25/30 from Smooth-on
Making Molds with Pourable Silicone
This is my simple method of making a one part/single sided mold using Oomoo 25, a liquid silicone.
- Find the object that you are molding (known as the mold master) and secure it to a flat & smooth surface.
- Make a mold box around your master to make a container or wall that the silicone can’t leak from. I have used Legos, foam/cardboard, and clay.
- Figure out the approximate volume of the space in your mold box, and measure out 1/2 that volume for each part of the silicone (For Oomoo, one part is pink, the other is blue). Make sure they are poured into a mixing cup in a 1:1 ratio by volume.
- Carefully stir the mix as to not get any air bubbles, for several minutes, or until everything is thoroughly mixed (if you’re using Oomoo, it should be a pale purple color at this point).
- Pour this mixture carefully over your master.
- Wait for the silicone to fully set before removing the mold box and the original master.
- Trim any bits that leaked or are in the way of the mold cavity, and you’re all ready to start casting!
You can also check out my advanced video on 2-part Molds & Casting with LEDs here for more information and a look at the general process as I do it.
Casting with Resin
Casting resin is actually pretty easy. The only things that can really go wrong are if you use too much of one part and not enough of the other, which can either lead to a casting that’s super brittle, or a cast that doesn’t fully set, is gooey, and can ruin your plastic molds (you can generally salvage your silicone molds). Just triple check the ratio you use, and you should be fine.
- Collect your supplies, you’ll need a mixing cup with volume measurements on the side, popsicle sticks to mix with, your resin of choice, your mold, and whatever colorant you’re using.
- Follow the mixing instructions of your resin. In my case I use Smoothcast 326, so I use 1 part A & 1 part B in a 1:1 ratio by volume.
- Thoroughly mix the two parts together for 1-2 minutes, or until fully combined.
- Add your colorant and/or glitter and mix that in completely.
- Pour your resin into the mold.
- (Optional) Add LEDs
- Wait for your resin to cure, then Tadaa! Gems.
Hooray! You can now do basic casting with resin. Wait… you don’t want clear gems? Keep scrolling for more information on adding color, glitter, & LEDs to your gems and casts.
Coloring Your Resin
One thing you’ll probably want to do if you’re making gemstones is to have them be pretty colors. There are a lot of ways to do this, and it’s really up to personal preference.
Liquid Resin Dye
Pros: Can be transparent or opaque. Mixes easily with resin. Many colors & varieties available including sparkles & neon.
Cons: Sometimes sticky. If you use too much it can keep your resin from hardening. Can be pricy.
Best For: Making opaque gems, gems with embedded sparkles & glitter
Pros: Cheap, and you get a whole bunch in the smallest size. Glows in the dark & under UV light! It distributes light really well if you’re using LEDs.
Cons: Sometimes the powder clumps up or doesn’t fully dissolve in the resin. Only comes in five neon colors that I know of.
Best For: LED gems, things you want to glow in the dark.
Examples: Slice of the Moon UV Powder
Pros: Can be really glittery & customizable to whatever nail polish or paint you have lying around.
Cons: When viewed from the side , the gem looks clear. LEDs look like points of light. Can be expensive if you use a lot of nail polish.
Best For: Sparkly gems without LEDs.
Use: You cast clear gems and then color the back side with nail polish.
Examples: Sinful Colors Nail Polish.
Other Things You Can Add
You can add all sorts of glitter to your resin. In the example on the left, I used big chunks of cellophane glitter and a couple of liquid resin dyes to make this ‘Blue Opal’ bangle. Be careful to not add too much or the resin may not cure properly.
You can get Cellophane Glitter here.
I do a lot of work with embedded LEDs in resin because so many of my cosplays require glowing gems or daggers. The simple version is that while your resin is curing, you stick an LED into it with the prongs of the legs out. Later you can wire it up to a simple or complex circuit, and voila, a glowing gem!
I plan on making a more in-depth tutorial about LEDs & resin a bit farther down the road.
Check out my Materials & Tools page for which LEDs & electronics I use.