Pot life of 2 pack paints

Posted in Firwood Hints and Tips by Firwood Paints Ltd on July 27th 2015

Paints cure by differing methods and for two pack paints the curing mechanism is a chemical reaction between the base paint and the curing agent.

When mixing two pack paints there is a limited time period from initial mixing when the paint is suitable for application and this is known as the pot life.A two part paint consists of a base component and a catalyst or hardener component.The two components are mixed together to activate a chemical curing process.The pot life of the paint is the period of time from first combining / mixing the two parts of a paint system to the point that the paint is no longer useable.The material may still be liquid after this time and appear to be useable but the properties will be affected after the stated pot life. Users of two pack paints should refer to the product instructions to ensure that any paint they mix can be applied within the time limitation of the pot life.

The pot life of a two pack paint can be found on the Technical Data Sheet relating to the product and the package label. This is a guideline only; it is based on application of the paint at a temperature of 20°C.The pot life will be extended at lower temperatures but drops significantly at higher temperatures. Typically a pot life of two hours at 20°C will drop by half for every increase in temperature of 10°C. So the same material will have a pot life of 1 hour at 30°C and 30 minutes at 40°C.

For some product such as high solid paints the end of pot life is indicated by an increase in viscosity of the coating. It will eventually become too thick to apply, however, not all paint systems increase in viscosity after the pot life has expired.These coatings may initially look fine if they are applied after their pot life but will fail after the curing process. An experienced paint sprayer will always mix just enough paint to comfortably apply within the pot life of the coating so as to reduce product wastage.

Coatings such as 100% solids epoxies will significantly increase in temperature when first mixed. This is as a consequence of the chemical reaction between base paint and curing agent. Care should be taken when handling the mixed paint as the product will be hot to touch.

To use a two pack coating beyond the product pot life will affect the flow of the product, the finished gloss level and will significantly affect the performance of the paint. Save money, time and a poor finish by paying attention to this important issue when using two pack paints.

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