Why Didn’t My Resin Cure? The Most Common Mistakes Behind It

When resin doesn't harden, it can be frustrating – time, materials, and effort go to waste. Here's a breakdown of the most common reasons why it happens and how to avoid it next time.

1. Incorrect mixing ratio

Every resin has a specific weight-based ratio of components A and B – both parts must be weighed accurately to the gram.

Sometimes, the wrong column in the ratio chart is used, A and B are reversed, or a volume ratio is mistakenly used instead of a weight ratio. Even small mistakes can prevent proper curing.

2. Too small amount

Always mix at least 50 g of resin. With smaller amounts, weighing errors are more likely – a half gram off makes a big difference when mixing just 10 grams. Also, the chemical reaction may not start properly in small quantities.

3. Inaccurate weighing

Precision is key – even a one-gram difference can ruin the result. Check if your scale is accurate: has it ever fallen? Are the batteries weak? Even without warnings, it may be inaccurate. We recommend replacing the batteries every 3 months.

4. Insufficient mixing

Mix thoroughly for at least 3 minutes – including the sides and bottom of the cup. Then pour into a second cup and mix again. Poorly mixed resin may not cure evenly or may remain uncured in some areas or casts.

5. Too much pigment

Each pigment has a maximum allowed volume in relation to the resin – we provide this information for all our colors. Too much pigment = disrupted chemical balance, resulting in soft or liquid resin.

This also includes using pigments that are not meant for resin.

6. Incorrect curing conditions

Each resin needs a specific curing time and temperature. Curing can take 12 to 72 hours – check the product info. This timing assumes correct temperature and proper mixing.

The temperature of both the environment and the resin should stay stable between 20–25 °C (not above 27 °C). Below 20 °C, the reaction slows or stops; above 25–27 °C, it may cure too fast. Temperature must remain steady throughout the curing process.

Also check humidity – it should be under 30–40 %. Higher humidity may cause surface blemishes or a sticky finish. Some resins like Fluid, 5-five, and EPOXYTABLE 10 have been tested up to 60 % humidity without damage.

7. Moisture or grease

Molds, tools, and workspace must be dry and clean. Moisture or grease can prevent proper curing.

8. Use of unsuitable materials

Never embed anything in resin that contains water, oils, waxes, or releases chemicals or dyes. Only use recommended pigments and decorations. If you're unsure, contact us and we'll help you choose the right materials.

Want to be sure your next resin project cures correctly? Follow the instructions, weigh carefully, monitor temperature – and don’t rush. Even a small mistake can cause major issues.