This is Part 4 of a series of blog posts on how you can learn how to make resin artisan keycaps. In this post, I’ll use the two-part silicone mold from Part 3 to make a multi-shot resin keycap. I’ll discuss materials and equipment, safety, colorants, and techniques. In Part 5, we’ll cover the final finishing steps!
Important: Read Part 3 First
Please make sure you’ve completed Part 3: Making a Keycap Mold before proceeding.
The absolute most important thing about casting resin is SAFETY. Resin is highly toxic. The fumes are toxic to breathe. If it gets on your skin, it will cause chemical burns (viewer discretion advised). You do NOT want to get this stuff on literally anything except the intended receptacles. In fact, if at all possible, do not cast resin in your home. Some artisans have workshops set up in a garage or outbuilding. I know this isn’t always practical or even possible, but take the precautions seriously. This cannot be understated.
Resin is Dangerous!
Before you read any further, go back to Part 1 – Getting Started and Minimum Equipment and (re)read the section on how dangerous resin is. Before you even think about buying any resin, stock up on PPE and learn about precautions.
Do not, under any circumstances, cast urethane resin in your bedroom, dining room, kitchen, at your computer desk, or in any commonly used living space.
Make sure you have plenty of ventilation. Open doors and windows, and use fans to direct airflow outside.
Wear all the protection. Any time the resin is in a liquid state, wear a ventilator and nitrile gloves. Keep pets, children, spouses, and any other living beings besides yourself out of the vicinity.
Always practice diligence.
Resin Casting Materials
Did you read the section about safety? If not, go back and read it.
The materials necessary for casting resin keycaps are listed in Part 1 – Getting Started and Minimum Equipment in the Basic Resin Casting Supplies section. Rather than repeat the list ad nauseam, make sure to (re)read that part of the first article in this series.
In addition to the protective equipment, resin, colorants, and workspace materials, I recommend using mold release spray. I mentioned this in Part 3 – Making a Keycap Mold. You’ll want to use mold release on — you guessed it — your silicone mold. You’ll be able to remove the casted keycap from the mold more easily while also avoiding damage to any fiddly, intricate bits of the mold.
Preparing the Keycap Mold
In Part 3, I shared how to cast a two-part silicone mold: the stem cavity, and the sculpt mold. Lightly spray both inner parts of the mold with mold release. Use foam swabs or foam Q-tips to gently distribute the mold release to ensure nooks and crannies are coated, and to remove excess. Excess mold release will affect the texture of your finished castings, so use a light touch.
How to Cast Multi-Shot Resin Artisan Keycaps
As I’ve mentioned before, a multi-shot keycap is composed of several different resin coloring, mixing, and curing layers on top of one another. In the photos for this tutorial, I used Smooth-Cast 326 urethane resin which comes in two parts, has a pot life (liquid state) of 7-9 minutes, and a cure time of 60 minutes.
If this is your first time casting multi-shot keycaps, I actually recommend that you use Smooth-Cast 327, which has a slightly more generous pot life of 10-20 minutes (mainly dependent on ambient temperature; warmer means shorter pot life). The cure time is longer as well, so it requires a bit more patience. However, the wait is worth the additional workable time if you’re just getting started. Rushing leads to accidents, and accidents lead to injury. Mistakes resulting from impatience are unsafe and easily avoidable.
Prepare Your Materials
The pot life timer starts counting down as soon as the resin (Part A) and hardener (Part B) contact each other. Until then, the two parts are inert and you have as much time as you need to get ready. Take that time to make sure you have everything prepared so you can move efficiently once you start mixing.
Put on your PPE (ventilator, nitrile gloves) and get your workspace ready. Set out your Part A and Part B. Get out two small disposable or silicone containers. I use small plastic cups (one cup will be for measuring Part A, and one cup will be for measuring Part B and mixing Part B with colorant and then adding Part A).
Make sure your workspace is protected. Have shop towels handy. Place your silicone sculpt mold on some kind of moveable, cleanable surface like a glass or porcelain tile. This is especially important if you’re using a pressure pot, since you will need to quickly transport the mold into the pot while keeping it as stable as possible. Even if you aren’t using a pressure pot, using a tile to catch drips or overspill makes cleanup much easier.
Since this tutorial addresses multi-shot techniques, you will not cast resin into the stem cavity yet, so there’s no need to put it on the tile for the first shot.
Have your resin colorant ready. For the keycap in this tutorial series, I used UVO colorants, which are highly concentrated and opaque.
While Smooth-Cast does list volume-based mixing ratios, keycaps are so small that I generally work with very small amounts of resin at a time. I personally prefer to measure by weight with a sensitive scale because it’s more precise. I weigh to the hundredth of the ounce. I also use a calculator since the weight ratio is not 1:1. I have a table calculator because I don’t love getting resin on my phone.
You can measure by volume if you prefer, but make sure you use something like a pipette or a graduated cylinder to ensure accuracy. When dealing with small volumes, if the ratios are a little bit off, you may have problems during the curing phase. You likely won’t even know about the problems until you demold your keycap hours later, and find out that it never fully hardened (and never will). Mistakes made during mixing are often irreversible because you don’t realize your mistake until too late.
Get out a stir stick, two pipettes, a toothpick, and a couple of small foam Q-tips. If you’re measuring by weight, get out your scale and calculator. If you’re measuring by volume, you will need multiple measuring receptacles: one each for Parts A and B (since measuring them in the same container will cause residual amounts to touch and begin to cure).
Prepare Resin (Part A) and Hardener (Part B)
You will mix the colorant and Part B together, and then add Part A. I like to add colorant to the empty cup first. Because I use a toothpick to add drops of resin, adding the colorant first means I don’t need to worry about contaminating my colorant with resin accidentally.
Assuming you are casting one keycap, you won’t need very much colorant or resin, especially if you’re doing multiple shots. Use the toothpick to dab a drop or two of colorant into one of your empty mixing cups. It doesn’t take much — if you’re using UVO, it only takes 1% of colorant to resin to yield solid color. I used white colorant because the first shot was the eggs in the nest. Since your mold’s opening is on the bottom, you will layer your resin shots starting with the colors at the top of the sculpt and working your way inward and toward the bottom.
If you are measuring by weight (which is my preferred method), set the cup with the colorant in it on your scale and zero it.
Vigorously shake your Part B bottle before opening. After shaking, unscrew the cap for Part B and use a pipette to add a small amount of hardener to the cup with the colorant on the scale. Make sure you take note of the weight (or volume), as you will need to know this measurement in order to correctly measure Part A at the appropriate ratio.
Important: volume and weight mixing ratios are not the same! Check the instructions on your resin and make sure you adhere to the correct ratio.
Use a stir stick to thoroughly mix the colorant and Part B. Make sure it is uniform and there are no streaks. Once mixed, set it aside.
Place your other empty cup on the scale and zero it (if measuring by weight). Consult your resin’s instructions for the proper weight ratio of Part A to Part B. If you’re using SmoothCast 327 (or 325 or 326) as recommended, the ratio is 115A:100B. Since you dispensed Part B first, multiply the weight of Part B by 1.15 on your calculator. This will the target weight for Part A.
Vigorously shake the Part A bottle. Use a pipette to add Part A to your cup until it reaches the target weight. I usually then add a drop or two more to account for some of the liquid sticking to the sides of the cup when I pour it into the Part B cup.
Then add Part A to Part B. This is when the pot life timer starts. Stir thoroughly until the colorant is evenly distributed. Insufficient mixing will result in streaks of color in the finished product.
Working quickly but carefully, use a pipette to dispense resin into the area of your keycap mold that you want to be this color. For me, this was the cavity for the eggs. If you need to work with smaller amounts of resin, use a toothpick. Make sure resin is covering intended areas of the mold sufficiently.
If you get resin anywhere in the mold that you don’t want it to be, you can clean it up with a small foam Q-tip. Or if it isn’t touching the resin that you DO want, you can leave it alone to cure. Once cured, you can easily remove unwanted bits with tweezers.
Now let the resin cure. If you do not have a pressure pot, set your mold somewhere safe on your workspace. I like to cover it with a piece of paper so that it doesn’t collect any particles from the air. Anything that gets into your mold will be cured into the resin permanently (either now, or in a future shot).
If you have a pressure pot, transport the mold (on the tile) into the pot and seal it completely. Then pressurize the chamber. I usually pressurize to 40-45 PSI. Try not to jostle the pot, especially if it was made from a converted paint mixer and has wheels (like mine, shown below).
And now you wait! The cure time will be listed on the packaging for your resin. Set a timer for the amount of time in the instructions. Try not to go over the time for multi-shot keycaps if it’s not the final shot. If the resin cures fully and completely sets, it will be slippery where it was exposed and can sometimes cause the next shot not to adhere properly.
After the cure time has elapsed, get your sculpt mold out and prepare for the next resin shot.
Repeat for Every Resin Shot
At this point, repeat the steps above for each different colored shot of resin you want to layer on. My second shot was the brown nest.
The third shot was the beetle. This is a slightly awkward shot because it’s somewhat on the edge of the keycap. For filling small areas, use a toothpick and let capillary forces pull drops of resin into the cavity where it should flow. It will distribute itself if you add the right amount. It will be attracted to the silicone, so even if you have areas where it would turn a corner or climb an edge, it will be naturally drawn into the recesses of the mold.
You can cure with the mold on its side if necessary, to ensure the resin doesn’t drip. I cure the beetle at an angle by leaning the mold against a small object.
The Final Shot and Stem Cavity
While the penultimate shot is curing, prepare the stem cavity part of your silicone mold. Use a small amount of mold release. You can use a foam Q-tip to coat the inside of the stem cavity itself.
When you set out your sculpt mold, make note of the corner that is marked or shaped differently. This indicates how to line up the two parts of the mold. I like to set my stem cavity mold next to the sculpt mold with the marked corners lined up next to each other. This way, I can just flip the stem cavity over quickly to close the mold. Swiftness is always essential.
For the final shot, fill the mold all the way to the top. The stem cavity part of the mold will displace some of the resin, so make sure your mold is on the tile to collect overspill. Displaced resin will come out of the sprue holes in the stem cavity and drip. Err on the side of more rather than less. If you use too little resin, air will be trapped in the mold and cure into bubbles and flaws.
Using a pipette or even just a stir stick, fill the stem — and maker’s mark, if you have one — with resin. Tap it gently to encourage air bubbles to float to the top.
You can use a lighter or small butane torch to gently pop any tiny bubbles on the surface of the resin. Then quickly (but steadily to avoid spilling) place the stem cavity on the sculpt mold. Excess resin will come out of the sprue holes.
Set the mold for the final cure, either somewhere safe or in the pressure pot. For the last cure, I generally leave the keycap untouched for at least 15-30 minutes longer than the listed cure time.
The Exciting Part: Demolding
Now it’s time to demold your keycap. First make sure the resin is sufficiently cured by checking the state of any resin that spilled when closing the mold. It should be hard to the touch, though it may still be very slightly flexible. It should not hold fingerprints.
Gently remove the stem cavity and overspill. Then carefully extract your keycap.
Congratulations on casting a multi-shot resin keycap!
In the next part of the tutorial, I’ll share how to sand and finish your keycap and then you’ll be done!
I make artisan keycaps, miniature foods, charms and jewelry, dioramas, digital art, and sell things in my shop. I also write blog articles describing my process and showing tutorials, and announce new products, limited raffle sales, giveaways, and more on Bluesky, Instagram, and in my email newsletter.
If you have questions about the tutorials or inquiries about art pieces that might be available for sale, you can mention me on Blueksy or send me an email. (Please do not DM me on Instagram, as I no longer check DMs there.)