How to Mix Epoxy Resin Correctly: Ratio, Time and Tips

Almost every resin problem — sticky spots, soft centres, cloudy patches — starts in the mixing cup. The good news: mixing correctly is simple once you know the three things that matter. Measure by weight, mix long enough, and work at the right temperature. Here's exactly how to do each one.

Know your ratio: 2:1 or 3:1

The ratio on your kit tells you how much resin (Part A) to use for each part of hardener (Part B):

• 2:1 — 2 parts resin to 1 part hardener. Used by Vitro 2:1 for coating, trays, coasters and jewellery.
• 3:1 — 3 parts resin to 1 part hardener. Used by Flex 3:1 for deep pours and flower blocks.

Never mix resin from one ratio with hardener from another, and don't "add a little extra hardener" to make it set faster — the ratio is a chemical recipe, not a strength setting. Not sure which you need? Read 2:1 vs 3:1 Epoxy Resin.

Measure by weight, not by volume

Fusion Resin kits are formulated to be mixed by weight. Resin and hardener have slightly different densities, so 2 cups of resin and 1 cup of hardener is not the same as 2 g to 1 g. Using a scale removes the guesswork.

Quick weight chart

The formula: for 2:1, Part A = total × 2 ÷ 3. For 3:1, Part A = total × 3 ÷ 4. The rest is Part B.

💡 Pro tip: Place the cup on the scale and press tare (zero) before each part. Pour Part A first, tare again, then pour Part B. Pour slowly near the target — it's easy to overshoot.

How to mix, step by step

1. Use a clean, dry cup with straight sides and a flat bottom. Any water or dust ends up in your piece.
2. Stir slowly for 3–5 minutes. Fast whipping adds air bubbles. Slow, steady circles are better.
3. Scrape the sides and bottom every 30 seconds. Unmixed resin hides in the corners and causes sticky spots later.
4. Watch it turn clear. Streaks or swirly lines mean it's not mixed yet. Keep going until it looks uniform.
5. Double-cup it. Pour into a second clean cup and mix for one more minute. This is the single best habit for avoiding soft spots.
6. Add colours now, in small amounts, after the resin is fully mixed.

Working time: how long you have

Once Part A and Part B meet, the clock starts. Pot life is how long the mix stays pourable:

These are typical times at room temperature. In hot Indian summers resin thickens faster, and large batches heat up in the cup — so mix smaller amounts and pour soon after mixing.

Temperature and humidity in India

• Summer: work in the cooler part of the day, keep resin out of direct sun, and pour soon after mixing.
• Winter: cold resin turns thick and holds bubbles. Warm the sealed bottles in a bowl of warm water for 10–15 minutes before mixing (keep water away from the caps).
• Monsoon: humidity can cause cloudy or tacky surfaces. Work in a dry room, and cover pieces while they cure.

Mixing mistakes to avoid

• Measuring with spoons or by eye
• Stopping before the streaks disappear
• Scraping the leftover film from the cup walls into your pour after mixing
• Mixing a huge batch in one go when you only need a little at a time
• Adding too much pigment — keep colours to a small amount

If something has already gone wrong, see Why Is My Resin Sticky?

Clear instructions, simple ratios.

Vitro 2:1 for coating and Flex 3:1 for deep pours — both mixed by weight for a reliable cure.

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FAQs

How long should I mix epoxy resin?

Mix slowly for 3–5 minutes, scraping the sides and bottom, then transfer to a second cup and mix for another minute.

Can I mix resin by volume?

Fusion kits are designed to be mixed by weight. Measuring by volume can upset the ratio and lead to soft or sticky results.

What happens if I add more hardener?

It won't cure faster or harder. An off ratio usually leaves the resin sticky, soft or brittle. Always follow the ratio on the kit.

Why does my resin get hot in the cup?

Mixing starts a chemical reaction that gives off heat. Bigger batches heat up more, which shortens working time. Mix only what you can pour soon.