Why You Should Not Mix Old and New Batches of Resin

Do Not Mix Old and New Batches in the Same Container

Keeping your resin projects flawless means paying close attention to the materials you use. One common pitfall is combining old and new resin batches in the same container, which can threaten both the result and the long-term quality of your work.

Why Mixing Old and New Resin Batches Is Risky

Each batch of resin can have slight variations in composition due to age, potential contamination, or changes in storage conditions. Mixing an older resin with a newly opened one increases the risk of chemical imbalances, uneven curing, inconsistent clarity, or unwanted yellowing. It can also introduce dust or moisture that might have entered the old container, causing problems in setting and finish.

Best Practices for Resin Storage and Use

To avoid these issues, always use clean, clearly labelled containers for each batch. Store your resins tightly sealed in a cool, dry area, out of direct sunlight to minimise premature ageing. When starting a new project, measure and mix only what you need from a single, well-stored batch. If you occasionally have leftover resin, resist the temptation to pour it back into the main supply.

Label each bottle or pot with the date of opening.
Close containers immediately after use.
Do not transfer unused, mixed resin into original containers.

When This Matters Most

The risk of issues rises with projects that require maximum clarity, strength, or a uniform finish—like river tables or deep cast artistic pieces. For these, using a reliable product such as Epoxytable 10-Ten and handling it as recommended helps maintain stability and beauty.

Related guides

How To Store Resin

By keeping old and new resin batches separate and following smart storage practices, you give every casting and coating project its best chance for a consistent, professional result. For further advice on getting the most from your resin materials, see our full guide on how to store resin.