How to Mix Epoxy Resin Correctly: Ratio, Mixing Time, Bubbles and Curing
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Successful epoxy resin work begins with accurate measurement and complete mixing. A beautiful mould or pigment cannot compensate for an incorrect ratio or poorly mixed components. Always follow the instructions for your exact resin, including whether the ratio is by weight or volume.
1. Read the product instructions
Check the resin-to-hardener ratio, recommended batch size, working temperature, pot life, pour depth and cure time. A 2:1 ratio by weight is not necessarily the same as 2:1 by volume. Do not use a ratio from another resin product.
2. Prepare tools and workspace
Use a suitable scale or measuring system, clean mixing cups, stir sticks, gloves and a level work surface. Make sure the cups and mould are clean and dry. Keep the work area within the manufacturer's temperature range and provide the ventilation and protective equipment required by the product SDS.
3. Measure and mix
- Measure each component accurately using the specified ratio and units.
- Combine the components in a clean cup.
- Stir slowly but thoroughly for the time recommended, scraping the sides and bottom.
- If the manufacturer recommends a second-cup method, transfer the mixture to a fresh cup and mix again.
- Use the mixture within its stated working time. Do not assume pot life in the cup equals the time available in a thin pour.
Explore ArtOrnate resin and measuring and mixing tools. Different formulations have different working and curing requirements.
4. Reduce bubbles
- Stir steadily rather than whipping air into the mixture.
- Pour in a controlled, thin stream where the product instructions allow.
- For detailed moulds, consider a small initial layer to help wet out fine areas.
- Follow the resin manufacturer's advice on bubble removal. Do not apply a torch or heat gun unless the product, mould and project method permit it; excessive heat can damage moulds or create safety hazards.
- Use dry pigments and additives confirmed compatible with the resin.
5. Pour and cure correctly
Check that the mould is level and that the resin is suitable for the planned thickness. Coating resin, standard casting resin and deep-pour resin are not interchangeable. A thick mass can overheat if the product is not designed for that depth. Protect the pour from dust and leave it undisturbed for the full cure period specified by the manufacturer.
Common problems and checks
| Problem | What to check |
|---|---|
| Sticky or soft resin | Ratio, measuring units, incomplete mixing, temperature and cure time |
| Many bubbles | Mixing speed, moisture, pour method and product instructions |
| Cloudy finish | Moisture, temperature, contamination and resin compatibility |
| Cracks or overheating | Batch size, pour depth, temperature and suitability for casting thickness |
| Uneven cure | Accurate measurement, scraping sides and base, and full mixing |
Frequently asked questions
Can I add extra hardener to make resin cure faster?
No. Changing the specified ratio can cause a failed cure and may create other problems.
Can I mix resin by eye?
No. Use the measurement method and ratio stated by the manufacturer.
Why is resin still sticky?
Check the ratio, mixing, temperature and stated cure time. Do not coat or handle it as finished until the cause and safe next steps are clear.
Can all epoxy resins be poured thickly?
No. Check the maximum recommended pour depth and batch size for the exact formulation.
Related: choose resin for silicone mould casting, working time vs cure time and silicone moulds.
Use a repeatable mixing checklist
Before each batch, confirm the resin and hardener names, ratio, measurement units, recommended temperature, pot life and maximum batch size. Weigh components into separate containers if that helps prevent measurement mistakes, then combine them and mix for the specified duration. If the instructions call for transferring to a second cup, do so before pouring. Keep a note of the batch and the time mixing began.
When a test piece fails
Review one variable at a time: ratio, measurement method, mixing, room conditions, additive compatibility and cure time. Do not pour another layer over a failed piece until you have checked the resin maker's recovery advice. For additional diagnosis, use the resin troubleshooting guide and confirm that the selected product is appropriate for the casting depth.