Recommended technique

Most sticky spots, soft patches, and cloudy cures come down to the same handful of technique mistakes — not a bad batch of resin. This guide covers the recommended technique for warming, measuring, mixing, and pouring so your cure comes out clear and fully hardened the first time.

Warm the resin before mixing (cold rooms only)

Epoxy reacts more slowly and flows less easily in a cold room, which makes it harder to mix evenly and pour cleanly. If your workspace is below 15°C, warm the resin (Part A) to around 30°C before mixing.

Two safe ways to do this:

• Warm water bath. Stand the sealed resin bottle in warm (not hot) water for a few minutes until it feels warm to the touch.
• Indirect room heat. Set the bottles a couple of feet from a space heater rather than right next to it, so they warm gradually rather than heating unevenly.

Don't overheat the resin. Warming it beyond a gentle warm-to-the-touch temperature shortens your working time and can cause the mix to start curing before you've finished pouring.

Measure by volume, not weight

Resin and hardener have different densities, so equal weights are not equal volumes — measuring by weight throws the ratio off even if your scale is accurate. Use graduated mixing cups and measure by volume instead.

Mixing ratios vary by product (for example, most Craft Resin lines are 1:1 by volume, Deep Pour is 2:1, and mould-making silicone is measured 1:1 by weight, which is the one exception). See our Mixing Ratio article for the exact ratio, working time, and cure schedule for each product before you start.

Mix thoroughly, scraping as you go

Under-mixing is the single most common cause of resin that stays soft or tacky. Pour both components into a clean container and stir slowly and deliberately — fast stirring introduces more air.

While you stir, repeatedly scrape the bottom and sides of the container with your mixing tool. Resin and hardener that cling to the edges of the vessel don't get caught up in the stir and never fully catalyze, which is exactly what causes soft, sticky patches later in the cure.

Keep in mind that larger batches give you less working time, not more — the exothermic reaction speeds up as volume increases. Mix in the batch size your product calls for rather than combining multiple kits at once.

Clear bubbles before the surface skins over

A quick, even pass of a torch or heat gun a few inches above the surface pops surface bubbles on thin coating layers (Arts & Crafts, Table Top). Keep the flame moving — don't linger in one spot, or you risk scorching or discolouring the resin.

This technique is for thin coating layers only. Never use a torch or heat gun on Deep Pour resin — the concentrated heat on a large mass can cause cracking and yellowing. Deep Pour benefits from covering the piece to keep dust off while it self-levels instead.

Pour cleanly

When you pour, leave the last bit of mixture in the container rather than scraping the sides and bottom into your pour. That residue is the same unmixed resin and hardener you were scraping loose while stirring — pouring it in defeats the point of scraping during mixing and reintroduces the risk of soft spots.

Step-by-step

1. Check the room temperature. Below 15°C, warm the resin to around 30°C before you start.
2. Measure resin and hardener by volume in graduated cups, using the ratio specified for your product.
3. Mix slowly and thoroughly, scraping the sides and bottom of the container repeatedly until the mixture is fully clear and streak-free.
4. Pour without scraping the container, leaving any residue behind rather than adding it to your project.
5. Clear surface bubbles with a quick torch pass on thin coating layers only — skip this step entirely for Deep Pour.

Related articles

• Mixing Ratio — How to Measure Resin and Hardener Correctly
• Why is my mixture getting hot?
• How to fix sticky spots of uncured resin