West System 205B Fast Epoxy Hardener (27.5 fl oz)

West System 205B Fast Epoxy Hardener (27.5 fl oz)

The West System 205 Fast Hardener is a medium-viscosity epoxy curing agent. It is useful in a majority of bonding situations, and at lower temperatures. This hardener produces a rapid epoxy cure that develops physical properties quickly at room temperature. Mix it with West System 105 Resin (sold separately) in a five-part resin to one-part hardener ratio. The resulting cured epoxy is a rigid, high-strength, moisture-resistant solid. The combination of 105 Resin/205 Fast Hardener has excellent bonding and coating properties. The West System 205 Fast Hardener is formulated to cure well at temperatures as low as 40-degree-F (4-degree-C). There are several things you can do to ensure a full cure when using epoxy in low temperatures.

Pre-Warm the Resin and Hardener

Cold temperatures increase an epoxy’s viscosity, making it harder to dispense, mix and apply. Warming resin and hardener reduces their viscosity, so they flow easily through their dispensing pumps. To pre-warm, place the resin and hardener containers under a warming lamp or in a warm-water bath. Pre-warmed resins and hardeners will not cling as much to your mixing equipment. They’ll also blend more easily, ensuring thorough mixing. A warmer, lower-viscosity mixture flows smoothly during application and readily penetrates porous surfaces.

Dispensing and Mixing Epoxy in Cold Temperatures

Always dispense 105 Resin (sold separately) and 205 Fast Hardener at the proper mixing ratio. Never alter the amount of hardener because this can seriously compromise the epoxy’s ultimate strength. Optional West System 300 Mini Pumps come ready to dispense the correct ratio of resin and hardener. One full pump-stroke of resin for every one full pump stroke of hardener is all you need to remember.

Preparing Surfaces

Between applying coats of epoxy, prepare the cured epoxy surfaces. When coating at cold temperatures, the slower cure can result in a waxy/greasy film on the surface of the cured epoxy, called amine blush. Remove this byproduct of the curing process before you apply the next coat of epoxy. Amine blush is easy to wash away with plain water and a 3M Scotchbrite pad. Don’t let the water evaporate. Dry the surface with plain white paper towels. Don’t use rags, because they can contaminate the surface with laundry softeners and anti-cling ingredients.

Allow the Epoxy Extra Time to Cure

Allow the epoxy additional time to cure before you remove clamps or stress the joints. As a general rule, double the cure time for every 18-degree-F (10-degree-C) drop in temperature. Allow even more cure time when for bonding pre-stressed joints, bent laminations, or joints that will undergo high loads. Elevate the temperature of the partially cured epoxy. This can help the resin and hardener complete their cross-linking. It’s a good way to boost the epoxy’s physical properties, even after a week at cold temperatures.