West System 207 Special Clear Hardener

Blush-free 207 Special Clear Hardener was developed for coating and fiberglass cloth application where an exceptionally clear, moisture-resistant, natural wood finish is desired. Blended with 105 Epoxy Resin, 207 Hardener will not blush or turn cloudy in humid conditions. Thin film applications roll out and tip off smoothly, requiring less sanding in preparation for finish coatings. 105/207 Epoxy has strong physical properties, so it can be used as a structural adhesive for gluing and laminating. 

Warm Weather Bonding with 207 Special Clear Hardener
WEST SYSTEM Epoxy’s cure times are based on an ambient temperature of 72°F. In warmer temperatures, epoxy cures faster. Here is what you need to know to ensure adequate working time when using epoxy in warm conditions:

Epoxy cures by a chemical reaction between the resin and hardener that releases heat, called an exothermic reaction. The larger the volume of epoxy the more heat that is generated. Many epoxy users have seen pots of epoxy smoke and bubble due to uncontrolled exotherm. The good news is you can prevent this. A good rule of thumb for gauging cure speed is that for every 18°F increase above 72°F, the working time and pot life will be cut in half. To maximize the working time of the epoxy, consider how much time you need and what temperature you’ll be working at, then select the hardener accordingly. For hot temperatures, we recommend 209 Hardener.

Warming the resin and hardener to about 80°F before dispensing will lower the epoxy’s viscosity, enhancing 207 Special Clear Hardener’s good flow characteristics. Epoxy resin and hardener cans may be safely warmed in a water bath.

Consider the temperature of your work area when deciding how deep to pour. At warmer ambient temperatures, the epoxy will cure faster and generate more heat. Again, limit the depth of each pour, especially when working in warm conditions.

Pouring
Limit the depth of the pour to ¼”. If a thicker layer is desired, allow the lower layer to set up before adding a new layer. Casting epoxy too thickly in a single pour, or casting more epoxy over a layer that has not set up can cause uncontrolled exotherm. This will ruin your project and could possibly destroy pieces of memorabilia you’ve placed in the casting.

Group Size A Hardener - use with 105-A Resin

Group Size B Hardener - use with 105-B Resin

Helpful tip: Use 300 Mini Pumps to always dispense 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.