Resin 101: Everything You Need to Know Before You Start
Updated Jun 2026TL;DR: Epoxy resin is a two-part chemical reaction, not a glue you can fudge. Get the ratio right, mix thoroughly, work in a warm room, and respect the cure window. Bubbles, tacky surfaces, soft cures, and yellowing all trace back to the same handful of root causes. This guide covers the chemistry, the ratios, the workflow, and the safety rules that keep resin work safe long-term.
Epoxy, UV, and polyester: what kind of resin are we talking about?
"Resin" covers three different chemistries in the craft world. They cure differently, behave differently, and are not interchangeable.
Epoxy resin. Two parts (resin and hardener) that react when mixed. Clear, hard, no shrinkage, low odour relative to the others, and forgiving for deeper pours. The default for coasters, jewellery, river tables, art castings, and anything that needs optical clarity. This is what most people mean when they say "resin" and it is what this guide focuses on.
UV resin. Single-part, cures in seconds under a UV lamp. Excellent for thin layers, jewellery bezels, and detail work where you want instant set. Brittle in thick pours, yellows faster than epoxy under sunlight, and the depth of cure is limited because UV light cannot penetrate far into the material.
Polyester resin. The fibreglass and boat-repair chemistry. Strong, cheap, fast, and aggressively smelly (styrene). Rarely used in craft because the fumes are punishing and the finish is dull compared to epoxy.
For everything that follows, assume epoxy unless we name otherwise.
A note on where to buy resin
YXE Creations does not stock two-part epoxy resin. Canada Post classifies it as hazmat and the shipping restrictions make it impractical to ship to most of our customers. Resin is widely available at local art supply shops, hardware stores, and specialty retailers, and that is where we send people for the chemical itself.
What we do stock is everything that surrounds the pour: graduated mixing cups, calibrated stir sticks, silicone molds in dozens of shapes, mica powders, alcohol inks, dried botanicals, glitter, and the dispensing tools that make accurate measurement possible. See the basic resin tools guide for the full kit list.
Mixing ratios: 1:1 vs 2:1, and why this is the number one cause of failure
Every epoxy resin has a specific ratio printed on the bottle. The two common ones are 1:1 (equal parts resin and hardener) and 2:1 (two parts resin to one part hardener). A few products use 3:1 or 4:1. Read the label before you mix anything.
Why it matters. Resin and hardener are not "the resin" and "the activator that makes it set". They are two halves of a chemical reaction. Every molecule of resin needs to find a molecule of hardener to react with. Get the ratio wrong and a portion of the mixture has nothing to bond to. That portion stays liquid or tacky forever.
The two common ratio errors.
- By volume vs by weight. Some products specify volume, some weight. They are not equivalent because the two components have different densities. If the label says "by weight", use a digital scale, not a measuring cup.
- Eyeballing the second pour. If the bottle says 2:1 and you pour close to 2:1, that is not close enough. A 5% error is enough to leave a sticky residue on the surface. Use graduated cups with clear markings or a scale.
If a piece cures hard underneath but stays tacky on the top, the ratio was off. There is no fix after the fact; the only options are sanding it down and pouring a fresh top coat, or scrapping the piece.
Pot life vs cure time
These are two different numbers and beginners confuse them constantly.
Pot life is how long you have, after mixing, before the resin starts to thicken in the cup. Typical pot life is 20 to 45 minutes for casting resin and as little as 5 minutes for fast-cure formulas. Once pot life ends, the resin gets hot in the cup (the exothermic reaction is accelerating), thickens fast, and stops self-levelling in the mold.
Cure time is how long until the piece is fully hard and demoldable. Typically 12 to 24 hours for handling, 48 to 72 hours for full cure. Some deep-pour resins take a week to reach final hardness.
Plan your pour around pot life, not cure time. If you have 30 minutes of pot life and you want to add three layers of colour, you have 10 minutes per layer. Mix smaller batches if you need more time per layer.
Temperature and humidity
Resin is sensitive to environment, more than most beginners expect.
Temperature. Most epoxies want 70 to 75 F (21 to 24 C) for both the working room and the resin itself. Below 65 F (18 C), the resin gets thick, bubbles refuse to rise, and cure slows or stalls. Above 80 F (27 C), pot life shrinks dramatically and the reaction can run away in the cup, generating enough heat to crack the piece or smoke.
Cold bottle problem. If the resin bottle was stored in a cold garage or basement, warm it before pouring. A 15-minute soak in a sink of warm water (bottle sealed) brings it up to working temperature. Cold resin is the most common cause of cloudy castings and stubborn bubbles.
Humidity. High humidity (above 75%) can cause a hazy, milky surface called amine blush on some resins. Work in a dry space if you can, or run a dehumidifier in the curing area.
Bubbles, and how to get rid of them
Mixing introduces air. Pouring introduces more. Bubbles trapped in the cured piece are the most common cosmetic flaw in beginner resin work.
Mix gently and slowly. Stir in slow figure-eight patterns, not fast circles. Scrape the sides and bottom of the cup to make sure unmixed resin from the corners gets incorporated. Most resins need 2 to 3 minutes of stirring.
Let the mix rest. After mixing, let the cup sit for 3 to 5 minutes before pouring. Many of the bubbles will rise and pop on their own.
Heat gun or torch on the pour. A quick pass with a heat gun or a culinary torch a few inches above the surface pops surface bubbles. Keep moving; lingering scorches the resin. Do not use this technique on silicone molds with a thin wall, the heat can deform them.
Pressure pot. A pressure pot pressurised to 40 to 60 psi during cure compresses any remaining bubbles down to invisible size. This is how professional jewellery and dice makers get glass-clear results.
Vacuum chamber. A vacuum chamber pulls bubbles out of the mixed resin before pouring. Useful for art casting and for resins that foam during mixing.
For a deeper dive on diagnosing bubbles, cloudiness, sticky surfaces, and soft spots, see troubleshooting common resin problems.
Demolding: when to pull the piece
Silicone molds release resin cleanly when the piece is fully cured. Pull too early and you get fingerprints, dents, and warped edges.
The thumbnail test. Press a thumbnail into a hidden corner of the piece while still in the mold. If it leaves a mark, the resin is not ready. No mark, fully hard, ready to demold.
Typical demold windows.
- Thin layer (under 5 mm): 12 to 18 hours
- Medium pour (5 to 20 mm): 24 to 36 hours
- Deep pour (above 20 mm): 48 to 72 hours, sometimes longer
Casting resins formulated for deep pours cure slowly on purpose to prevent overheating. Doing a deep pour with a fast cure resin will crack the piece or set off the smoke alarm.
Releasing the piece. Flex the mold gently from the outside in, working around the edges. Resist the urge to pull from the top; that distorts shapes. If a piece refuses to release, give it another 12 hours, the cure is not done.
Finishing: sanding and polishing
A demolded piece almost always has a flat dull bottom (the side that faced the mold opening) and crisp shiny sides (against the silicone). Most people want all sides glossy. That means sanding, then polishing.
Sanding sequence. Start at the lowest grit needed to flatten the surface (180 or 240 for a rough bottom, 400 for light cleanup) and work up through 600, 800, 1000, 1500, 2000, and 3000. Skipping grits leaves scratch marks that the next grit cannot remove. Wet sanding (a spray bottle of water and waterproof sandpaper) keeps the dust down and the surface cool.
Polishing. After 3000 grit, the surface is matte and uniform. A plastic polish or a car polishing compound on a soft cloth or a buffing wheel brings it back to glass. Two coats with a clean cloth between is typical.
The shortcut: doming coat. Pour a thin layer of fresh resin over the sanded surface. The new resin self-levels and cures glossy without polishing. Useful for coasters, art panels, and anything flat. Not useful for jewellery or anything with a complex shape.
Adding colour and inclusions
Mica powders, alcohol inks, pigment pastes, glitter, dried flowers, and other inclusions are added at the mixing stage. A few guidelines.
Pigment load. Most colourants want 1 to 6% of the total resin mass. Above 10%, the colourant interferes with the cure and the piece stays soft. Mica powders are the most forgiving; pigment pastes are the most likely to cause cure problems.
Alcohol inks. The alcohol carrier evaporates during cure and can leave streaks. Use sparingly; a few drops go a long way.
Inclusions. Dried botanicals and paper need to be fully dry; trapped moisture causes cloudy halos around the inclusion. Pre-seal porous inclusions with a thin coat of resin and let it cure before the main pour.
For more on choosing and using fillers, see comprehensive guide to sourcing fillers for resin art. For mica specifically, mica powder 101.
Safety
Epoxy resin is not toxic in the casual sense. It will not poison you from a single exposure. The real risk is repeated unprotected exposure, because epoxy can sensitise the skin over time. Sensitisation means the immune system has decided this substance is an enemy, and once sensitised, you develop a persistent contact allergy that does not go away. People who have been working with resin happily for years are not immune; sensitisation can show up at any point. Protect yourself from day one.
Nitrile gloves, not latex. Latex is permeable to epoxy and offers no real protection. Nitrile is the standard. Change them if they tear or if resin gets on the outside.
Respirator with organic vapour cartridges. A dust mask does nothing for resin fumes. A half-face respirator with organic vapour cartridges does. The cartridges have a shelf life once opened; replace them on schedule.
Ventilation. Work in a room with active airflow. A fan blowing across your workspace toward an open window is the minimum. A purpose-built fume extractor venting outside is better. This applies to every resin pour, not just the big ones; the fumes are the same.
No skin contact. If you get resin on your skin, do not use solvents to remove it; solvents drive the resin into your skin and worsen the exposure. Wipe with a dry paper towel first, then wash with soap and warm water.
Cured resin is inert. Once fully cured, epoxy is stable and safe to handle, sand (with dust protection), and wear against the skin. The hazard is the uncured liquid and the curing fumes, not the finished piece.
What to keep on hand
Beyond the resin itself (which you source locally), here is the support kit:
- Graduated mixing cups with clear markings, multiple sizes
- Calibrated stir sticks, ideally flat with a paddle end
- Nitrile gloves, a full box, change them often
- Half-face respirator with fresh organic vapour cartridges
- Digital scale that reads to 0.1 g
- Silicone molds in the shapes you want to make
- Mica powders, alcohol inks, or pigment pastes for colour
- Heat gun or culinary torch for bubble removal
- Drop sheet or silicone work mat
- Paper towels (more than you think)
- Sandpaper in the full grit range from 240 to 3000, plus polish
Frequently asked questions
Q: My resin cured tacky on the surface. What happened? A: Almost always one of three things. Mixing ratio was off (most common), the room was too cold during cure, or the resin and hardener were not stirred thoroughly enough. There is no fix after cure; sand the tacky layer off and pour a fresh thin top coat.
Q: How do I get the bubbles out? A: Mix gently, let the cup rest for a few minutes before pouring, and pass a heat gun or torch over the surface after pouring. For glass-clear results, a pressure pot during cure compresses any remaining bubbles invisibly small.
Q: Can I pour a thick piece in one go? A: Only with a casting resin formulated for deep pours. Standard "coating" or "doming" resins generate too much heat in thick pours and will crack, smoke, or yellow. Read the maximum pour depth on the bottle.
Q: Why is my resin yellowing? A: UV exposure, old resin (past its shelf life), or a resin formula that was not stabilised for UV. Store finished pieces out of direct sunlight, and check the bottle's expiry date before mixing.
Q: Do I really need a respirator for small pours? A: Yes. The fumes are the same chemistry whether the pour is one cup or ten. The risk is cumulative; small unprotected pours add up to sensitisation over time.
Q: How long does mixed resin keep? A: It does not. Once mixed, the reaction has started and the resin will harden in the cup whether you use it or not. Mix only what you will pour within the pot life window.
Q: Why does YXE Creations not sell the resin itself? A: Two-part epoxy resin is classified as hazmat for shipping, and Canada Post restrictions make it impractical to ship to most of our customers. We carry everything that goes around the pour (cups, molds, powders, fillers, dispensing tools) and we send people to local art and hardware stores for the resin itself.