Correct Dosing Ratios for Polyester Resin Catalyst

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Getting the catalyst ratio right is essential for strong, reliable results when working with polyester resin. An accurate mix ensures your repairs or builds are durable and properly cured.

Understanding Standard Ratios

The usual dosing range for polyester resin catalyst (hardener) is between 2% and 3% of the resin’s weight or volume. This means that for every 100g of resin, you should add 2–3g of catalyst. Precision is important, as too little can prevent full curing, while too much can lead to excessive heat and a brittle finish. Always confirm the manufacturer’s recommended ratio for your specific product before mixing.

Safe and Simple Measuring Techniques

To achieve the correct ratio, use digital kitchen scales for accuracy or measuring syringes if dosing by volume. Mix thoroughly to ensure the catalyst is evenly distributed. Many ready-to-use kits, such as the Resin Fibreglass Repair Kit – Complete Polyester Resin and Hardener Set, provide pre-measured resin and hardener to take out the guesswork—simply follow the included instructions for a smooth process.

When Precise Dosing Matters

For repairs on boats or pools, proper curing is critical for water and impact resistance.
When applying resin in cool or humid conditions, careful dosing ensures a consistent cure.
For beginners, kits with measured components can greatly reduce mistakes.

Related guides

How To Dose Polyester Resin Catalyst

Following accurate catalyst ratios is the foundation for every strong polyester resin repair. If you’re ready for a straightforward experience, consider a complete repair kit that includes the correct hardener proportions. For more guidance, see our hub on how to dose polyester resin catalyst.