The word “resin” is a general term that refers to viscous liquids that can permanently harden. But in the crafting world, we are generally referring to a thick, clear liquid that cures to create a crystal-clear layer. You’ll recognize brand names such as Easy Cast, Envirotex Lite, Lisa Pavelka’s Magic Glos, and Solarez. You might have seen this type of material coating tables in restaurants or coating small pendants. It’s also poured or cast into molds to create resin items such as paperweights, jewelry, or tiny figurines. But increasingly we’re using this material as a coating on polymer clay.
A note about the links. I’ve linked to an Amazon listing for the items in this article so that you can see what I’m talking about. Doing this saves me from having to take a photo. Obviously, shop around and order from whatever supplier makes sense where you live. If you’re outside the US, don’t order from Amazon.com! The links to Amazon, btw, are affiliate links which means they’ll pay me a little bit if you do order from them. But please don’t feel that it’s necessary. Buy from your favorite retailer!
What are the types of resin that you can use with polymer clay?
Two main types of resin are used with polymer clay. Both are used as a coating to protect the finish and give a thick, glossy shine. One is UV resin, and the other is epoxy resin. Both types of resin contain a plastic compound that will undergo a chemical reaction and become hard. The difference is what causes, or catalyzes, that chemical reaction.
UV resin uses ultraviolet light to trigger, or catalyze, the chemical reaction that causes the resin to become hard. You can use a light with a special ultraviolet bulb, such as a nail lamp or an ultraviolet flashlight. Because the sun also emits ultraviolet light, you can use the sun to cure your UV resin as well. I have the Lisa Pavelka UV Light and it works well.
UV resin usually hardens with five or ten minutes of light exposure. The stronger the light source, the faster the UV resin will cure. While sunlight will work, be aware that weak winter light and cloudy days can mean a slow or incomplete cure. Using sunlight to cure UV resin means you’ll have to go outside. Be aware that transporting your resin-coated pieces can be tricky. Also, it’s often just windy enough outside that you risk your lightweight polymer clay pieces being flipped over, ruining the resin.
Don’t pour your UV resin while sitting near a sunny window or even with strong light. Even ambient light has some ability to begin the cure process. UV Resin should always be kept in a dark cabinet and preferably in a dark bottle because strong light can cause it to cure, especially over time.
Brands of UV Cure Resin
Common brands of UV resin are Lisa Pavelka’s Magic Glos and this really fast-curing resin from China (their branding needs some work, but we all recognize that label design). Many people also love to use UltraDome resin, but I’ve not tried it.
Epoxy resin has two parts, one part being the resin material and the other part being the hardener (the catalyst). When the two parts (typically labeled A and B) are mixed in the correct proportions, the chemical reaction is catalyzed, and hardening begins.
Epoxy resin usually takes from 12 to 36 hours to cure. This is somewhat temperature dependent, and your pieces will cure faster in a warm room. But don’t assume that more heat is always better. You can’t speed-cure in an oven, for example.
For many processes with polymer clay, it would be great to be able to add more polymer clay after you’ve used resin and bake it once again. Can you do that? Sort of. Some brands of UV resin do have some heat tolerance, and you can give them a short, cool-ish bake. But you risk the resin turning yellow or even cracking and degrading. You should never bake epoxy resin.
Brands of Epoxy Resin
Doming, Coating, and Casting Resins
You’ll notice these terms are often applied to various brands of resin. Let me be clear. These are merely labels that describe how a resin behaves. These names don’t refer to chemical categories. For example, Easy Cast (a casting resin) and Envirotex Lite (a coating resin) have the same ingredients. There is also much overlap within these broad categories. You can easily use a doming resin to make small casts or use a casting resin as a coating. But there are some general points to be aware of.
(Note: there are many types of casting resins such as PMMA, acetal resin, and polyester resin, but they’re entirely different chemicals and usually used for completely different purposes than epoxy and UV resins.)
What is Doming Resin?
As resin hardens, it contracts and shrinks. This allows a thick coating of resin to sort of hump up as it cures, causing a doming effect. Some brands of resin have a stronger shrinkage factor than others. Resin with a strong shrink factor will produce a stronger doming effect.
A drawback of the doming effect is that some resins will pull away from the edges of what you’re coating. They’ll contract and bead up, even to the point of looking like drops of water on a freshly waxed car. If this happens, you’ll often need to apply several coats of resin to get even coverage.
Both doming and coating resins contract during the curing process and some brands are worse than others at giving poor coating coverage. If you’re frustrated with one brand, try another. Also be aware that some brands of polymer clay will be better at “grabbing” the resin than others. Doming resin can also cause thin polymer clay pieces to curl upward.
Coating vs. Casting Resin
The reason this distinction is sometimes made is because resin cures with an exothermic reaction. This means that one of the chemical by-products is heat. If a particular resin formulation is strongly exothermic, it cannot be used as a casting resin. Doing so means there’s too much heat in one space and you’ll get massive amounts of bubbles as the resin degrades while it cures. If you need to create a large casting, make sure to use a resin that’s specifically intended for casting.
While some resins are very thick and are formulated for casting, others are thin and intended to be used as a brush-on coating. Nail salons have been using UV resin for years. You can use UV-cure nail polish on polymer clay, in fact. Clear UV-cure topcoats are a great way to get a clear coating on polymer clay.
Troubles with Resin
While resin is an excellent clear coating, it does have some rather substantial drawbacks. Aside from being expensive and it’s messy to work with, here are some other issues.
Both epoxy and UV resins have a short shelf life, typically a year or less. Older resin turns yellow while in the bottle and if it’s old enough, might not cure completely.
Speaking of yellowing, uncured epoxy resin tends to turn yellow in the bottle with time. This doesn’t matter much when using resin over dark items. But the yellowing of resin will be very apparent over white polymer clay. After curing, ALL epoxy and UV resin will eventually take on a yellow color. This will happen much faster if the cured resin is exposed to high heat or UV light. Keep resin materials out of sunlight.
Soft or Sticky Incomplete Curing
If the resin material doesn’t cure properly (either due to age or improper mixing ratio), it will never fully harden and even can be sticky. Once that happens, it’s difficult or impossible to remove without ruining your item. If the item is only just a tiny bit sticky, you can sometimes make a new batch of resin and give it a thin coat on the surface. Be aware, however, that this layer can sometimes peel off in the future. (Adding a second coat to well-cured resin doesn’t seem to have the problem, however.)
Key to Better Mixing of Epoxy Resin
To get a complete cure with epoxy resin, you need to thoroughly mix perfect proportions. You’ll have less error if you mix up larger volumes. So save up several items so you can pour them all at once. Everyone has their own favorite ways to work with a material, but here are some tips that have worked for me.
- Measure the two parts into a marked medicine cup. Don’t dump out the first part before adding part two. Just add it to the top, using the correct lines on the cup. (eg. pour part A to the 10ml marking, then add part B to reach the 20ml mark) Try to use measuring cups that don’t have little tabs around the inside bottom. That makes it hard to scrape out the resin.
- Pour the cup’s contents into a clean disposable cup. Paper or plastic Dixie cups work nicely for this. (But buy them at the grocery, not Amazon…whoa they’re pricey there!) Use a stir stick to scrape as much out of the medicine cup as possible. Rather than popsicle sticks, use wooden coffee stirrers. They have a square bottom.
- Mix the resin together in a scooping motion, taking care to avoid whipping bubbles into the mix.
- Pour this mixture into another Dixie cup, scraping as much out of the previous cup as possible.
- Using a new stir stick, mix this resin mixture thoroughly. Doing this second cup and stick solves most mixing errors.
- Pour from this cup.
Resin is messy. It’s the kind of thing that you want to do in a dedicated space where children and pets have no access. It also takes a bit of concentration, so you don’t want to be interrupted while dealing with resin. Make sure to have a clean box to put over your epoxy-resin-coated items to keep dust from falling onto them during the 24-hour cure.
Resin flows like syrup, and if your surface isn’t level, the resin will spill over and make a mess. Make sure the table you’re pouring onto is level.
While spills clean up easily with rubbing alcohol, it’s easy to miss little spills because it’s clear. Wear an apron while you work with resin. It can get messy fast.
Due to the mixing process of epoxy resin or just due to the act of pouring itself, it’s common for resin to have lots of small bubbles. These need to be popped before you cure the resin. The best way I’ve found to remove bubbles is as follows:
- Get a pair of magnifying glasses so you can see up close.
- Let the piece sit for a few minutes so the resin can self-level, and the bubbles can rise to the surface.
- Use a heat gun or a candle lighter (the long type) and pass quickly over the surface. This will pop most of the bubbles. You can also use your breath through a straw. You’ll see bubbles pop that you didn’t even know were there. Be careful that you don’t make the resin overflow by blowing it around.
- Inspect again with the magnifying glasses. Look for any bubbles that are lodged down in crevices or textures. Use a needle tool to encourage them to surface.
- Repeat the heat gun step.
- Let self-level for a few minutes. Then cure.
Is Resin Toxic?
Neither epoxy nor UV resin is acutely toxic. Respirators are not required, and although the materials tend to smell bad, the fumes will not poison you. But you should minimize skin exposure and use proper ventilation when mixing and pouring resin. This is because the material tends to create hypersensitivity reactions in some people. In other words, it’s not toxic, but you can become very sensitive or allergic to it.
Two brands of epoxy resin, Little Windows Brilliant Resin and another one called Art Resin both advertise that they’re non-toxic. They’re not made from something particularly unique. They’re both made of the same general ingredients as the other brands of epoxy resin.
Mixing Things into Resin
You can mix mica powders into resin to make a beautiful shimmer. Powdered chalks or pigments can color resin as well, but can be grainy. Alcohol ink can be used to color resin. Most of the “resin pigments” that you see advertised on online marketplaces (such as this) are actually just packets of mica and pigment powder.
If you color UV resin with any powders or pigments, you might block the light’s ability to reach the resin and cure it.
Speaking of powders…have you seen my new Guide to using Powders with Polymer Clay?
Is Resin Compatible with Polymer Clay?
Because some materials like varnishes, paints, and glues can be softened by the plasticizers in polymer clay, compatibility with polymer clay is a common concern for clayers. Rest assured, both UV and epoxy resin work perfectly well on cured polymer clay. There are no short or long term interactions.
When Should You Use Resin?
Resin is best used when a thick, glassy layer is desired. Adding resin has somewhat of a magnifying effect and can make shimmery, sparkly polymer clay projects appear even brighter. It’s the perfect coating for the Holo Effect Technique. Resin also works well to fill shallow depressions to give the appearance of water in fairy gardens or to make dewdrops on leaves and petals.
Resin can make a good shiny coating, but if your item has a lot of texture, you’ll be happier using a varnish for this. Even light-bodied resin is still quite viscous and can make subtle texture disappear.
If your item is fairly smooth and you want a glass-like shine, any resin can give you this effect. Thin coats of brushed-on resin work well for this, too, but only if you have already removed the surface flaws. Brushing resin over bumpy work will just accentuate the bumps.
For alternatives to resin, check out my article on Understanding Clearcoats with Polymer Clay. You can also sand and buff smooth surfaces. While resin is faster, it has a very different effect. Sanding and buffing is only hard and time-consuming if you’re doing it wrong. Luckily, I have a Sanding and Buffing eBook that can help turn that around. I sand and buff some things and I resin coat others. They’re not interchangeable alternatives. Either way, you’ll love using resin with your polymer clay projects.