Dispensing and mixing WEST SYSTEM epoxy
To achieve a high-strength epoxy solid, it is essential to measure quantities of resin and hardener carefully and mix them thoroughly.
To obtain full cure, the curing process must be a controlled to ensure a thorough chemical transition into a solid. The following procedures apply whether applying the resin/hardener mix directly as a coating or modifying with fillers or additives.
This page covers:
Introduction to dispensing
Dispensing using WEST SYSTEM® Mini Pumps
Dispensing using weight or volume measures
Mixing resin and hardener
Tip for first-time users: try mixing small test batches first
Safety warning: curing epoxy generates heat
An accurate ratio is essential for a proper cure and the full development of physical properties. Dispense the correct proportions of resin and hardener into a clean plastic, metal or wax-free paper container. It is important not to use glass or foam containers. Doing so might cause exothermic heat build-up. Do not alter the mix ratio to try and adjust the cure time.
Dispense the correct proportions of resin and hardener.
Most problems related to the curing of epoxy can be traced to the wrong ratio of resin and hardener. To simplify metering, use calibrated WEST SYSTEM Mini Pumps to dispense the correct working ratio of resin and hardener.
WEST SYSTEM Mini Pumps have been specially designed to make dispensing the right amount of resin and hardener easier. Simply use one full pump stroke of hardener for one full pump stroke of resin. One full depression of each pump will give approximately 24g of mixed epoxy. Depress each pump head fully and allow the head to return completely before beginning the next stroke. Partial strokes will give an incorrect ratio.
Often, curing problems are caused by incorrect ratios so check you have it right before using the resin/hardener mixture on your project.
With Mini Pumps, use one full pump stroke of resin to one full pump stroke of hardener to get the correct ratio.
To measure 105 Epoxy Resin, 207 Special Clear Hardener™ or 209 Extra Slow Hardener™ by volume, combine three parts resin with one part hardener. By weight this would amount to 3.5 parts resin : 1 part hardener.
Thoroughly blend the two ingredients for 2 minutes or for longer in cooler temperatures. Be sure to scrape the sides and bottom of the pot with your stirrer when mixing. If you’re planning on using the mix for coating, quickly pour it into a roller pan to extend the open time after mixing.
Stir resin and hardener together thoroughly. Stir for at least 1 minute longer in cooler temperatures.
If you are using WEST SYSTEM epoxy for the first time, we recommend that you start with a small test batch before applying a mix to the job in hand. This will give you a feel for the mixing and curing process. It will also demonstrate the open time for the resin/hardener mix at the ambient temperature in your workshop. Once you are confident of the handling characteristics of the epoxy and that the mix ratio is correctly metered, move on to a larger batch.
It is important not to fill or cast layers of epoxy thicker than 10 to 12mm (or thinner if enclosed by foam or another insulating material). If you leave the mixed epoxy to stand for the full pot life in a plastic mixing cup, it will generate enough heat to melt the plastic.
If a pot of mixed epoxy begins to heat up, quickly move it outdoors and avoid breathing in the fumes. Wait until the material has cooled and the reaction is complete before disposing of the mixture.