Dispensing and Mixing
Careful measuring of epoxy resin and hardener and thorough mixing are essential for a proper cure. Whether the resin/hardener mixture is applied as a coating or modified with fillers and additives, observing the following procedures will assure a controlled and thorough chemical transition to a high-strength epoxy solid.
Dispense the correct proportions of resin and hardener into a clean plastic, metal or wax-free paper container. Don’t use glass or foam containers because of the potential danger from exothermic heat buildup.
DO NOT attempt to adjust the epoxy cure time by altering the mix ratio. An accurate ratio is essential for a proper cure and full development of physical properties.
Most problems related to curing of the epoxy can be traced to the wrong ratio of resin and hardener. To simplify dispensing and reduce the possibility of errors, we recommend using calibrated WEST SYSTEM Dispensing Pumps to meter the correct working ratio of resin to hardener.
Pump one full pump stroke of resin for each one full pump stroke of hardener. Depress each pump head fully and allow the head to come completely back to the top before beginning the next stroke. Partial strokes will give the wrong ratio. Read the pump instructions before using the pumps.
Before you use the first mixture on a project, verify the correct ratio according to the instructions that come with the pumps. Recheck the ratio anytime you experience problems with curing.
To measure 105 Resin and 205 or 206 Hardener by weight or volume, combine 5 parts resin with 1 part hardener. To measure 105 Resin with 207 or 209 Hardener by volume, combine 3 parts resin with 1 part hardener ( by weight, combine 3.5 parts of resin with 1 part of hardener).
If this is the first time you have used WEST SYSTEM epoxy, begin with a small batch test to get the feel for the mixing and curing process, before applying the mixture to your project. This will demonstrate the hardener’s open time for the temperature you are working in and assure you that the resin/hardener ratio is metered properly. Mix small batches until you are confident of the mixture’s handling characteristics.
Stir the two ingredients together thoroughly – at least 1 minute – longer in cooler temperatures. To assure thorough mixing, scrape the sides and bottom of the pot as you mix. Use the flat end of the mixing stick to reach the inside corner of the pot. If you are using a power mixer, occasionally scrape the sides and corners of the mixing pot while mixing. If you are going to be using the mixture for coating, quickly pour it into a roller tray to extend the open time.
WARNING: Curing epoxy generates heat. Do not fill voids or cast layers of epoxy thicker than 12mm – thinner if enclosed by foam or other insulating material. Several centimeters of mixed epoxy in a confined mass (such as a mixing cup) will generate enough heat to melt a plastic cup, burn your skin or ignite combustible materials if left to stand for its full pot life. For this reason, do not use foam or glass mixing containers or pour into confined spaces. If the pot of mixed epoxy begins to exotherm (heat up), quickly move it outdoors.
Avoid breathing the fumes. Do not dispose of the mixture until the reaction is complete and has cooled.