WEST SYSTEM® | Epoxy Basics 02 of 11
Measure resin and hardener accurately, then mix for at least one minute. Most cure problems trace back to one of those two steps.
Whether the mixture is going on as a coating or being thickened with fillers and additives, the procedure below gives a controlled, complete transition to a high-strength epoxy solid.
Ratios from the WEST SYSTEM® 105 System data. Guide only — refer to the current technical data sheet for full product specifications and suitability.
Pumps or measured volume
Dispense resin and hardener into a clean plastic, metal or wax-free paper container. Do not use glass or foam containers, because of the danger from exothermic heat build-up.
Do not adjust cure time by altering the mix ratio. An accurate ratio is essential for a proper cure and the full development of physical properties. To change cure speed, change hardener or change the temperature.
Most cure problems trace back to the wrong ratio of resin to hardener, so ATL recommends calibrated WEST SYSTEM Mini Pumps, which are set to deliver the correct working ratio. Pump one full stroke of resin for each one full stroke of hardener. Depress each pump head fully and let it return completely to the top before the next stroke — partial strokes give the wrong ratio.
Read the pump instructions before use, and verify the ratio according to those instructions before the first mixture goes on the project. Re-check the ratio any time you have a curing problem.
| Resin | Hardener | Measure | Ratio |
|---|---|---|---|
| 105 Epoxy Resin | 205 Fast or 206 Slow | By weight or volume | 5 : 1 |
| 105 Epoxy Resin | 207 Special Clear or 209 Extra Slow | By volume | 3 : 1 |
Confirm the ratio for your pack against the current product label and technical data sheet before mixing.
4 steps
Clean plastic, metal or wax-free paper. No glass, no foam. Size the batch to what you can apply within the open time for the temperature you are working in.
Scrape the sides and the bottom of the pot as you mix, and use the flat end of the mixing stick to reach the inside corner. Mix longer in cooler temperatures. If you are using a power mixer, still scrape the sides and corners as you go.
Pour the mixture into a roller tray as soon as it is mixed. Spreading it out dissipates exothermic heat and extends the open time; leaving it in the pot does the opposite.
Mix the resin and hardener completely first, then blend in fillers or additives. See Modifying Epoxy with Fillers and Additives.
Warning — curing epoxy generates heat. Do not fill voids or cast layers thicker than 12.7 mm (½ in), thinner again if enclosed by foam or other insulating material. Several centimetres of mixed epoxy in a confined mass such as a mixing cup will generate enough heat to melt the cup, burn skin or ignite combustible materials if left to stand for its full pot life. Do not use foam or glass containers, and do not pour into confined spaces. If a pot begins to exotherm, move it outdoors immediately, avoid the fumes, and leave it until the reaction is complete and it has cooled.
Test before you commit
Mix a small test batch before anything goes on the project. It shows you the hardener's open time at the temperature you are working in, and confirms the resin and hardener are being metered correctly. Small batches are the cheapest way to learn how the mixture handles.
If you cannot find an answer about selecting or using WEST SYSTEM products, contact ATL Composites on +61 7 5563 1222 or [email protected].
Laminating & pours
Most work is done in small batches of a few hundred millilitres, and that covers the large majority of jobs. Large laminating jobs are different, and they need planning, because a large batch cures faster than a small one.
Further reading: Big Batch Epoxy Mixing at Epoxyworks.
4 questions
No. The ratio is fixed by the chemistry, and altering it prevents a proper cure and the full development of physical properties. To cure faster, use a faster hardener or raise the temperature.
105 Epoxy Resin mixes 5:1 by weight or volume with 205 Fast or 206 Slow Hardener, and 3:1 by volume with 207 Special Clear or 209 Extra Slow Hardener. With calibrated Mini Pumps it is always one full stroke of each.
At least one minute, and longer in cool conditions. Scrape the sides, the bottom and the inside corner of the pot while mixing — unmixed material clinging to the wall is a common cause of soft or sticky patches.
The usual causes are an inaccurate ratio, incomplete mixing, or curing below the hardener's minimum recommended temperature. Re-check the pump ratio against the pump instructions, mix for longer, and confirm the working temperature suits the hardener.
Supplied by ATL Composites
Resin & hardeners
105 Epoxy Resin with 205 Fast, 206 Slow, 207 Special Clear and 209 Extra Slow Hardeners.
Dispensing
301 and 303 Mini Pumps, calibrated to deliver the correct working ratio of resin to hardener.
Fillers
Australian range: 410 Microlight, 411 Microsphere Blend, 413 Microfibre Blend and 417 Low Density Filler.
Additives
423 Graphite Powder, and 501 and 502 Pigments to tint the epoxy mixture.
Application tools
Static mixers, mixing sticks, flexible plastic squeegees, roller frames and covers, and mini syringes.
ATL Composites manufactures and distributes WEST SYSTEM epoxy in Australia.
View the WEST SYSTEM rangeGuide only. Refer to the current technical data sheet for full product specifications and suitability. Adapted from WEST SYSTEM instructional material (original guide). Read the product label and the current technical and safety data sheets before use.
Guide 02 of 11
Talk to ATL Composites about your process on +61 7 5563 1222 or [email protected].
WEST SYSTEM®, 105 Epoxy Resin®, 205 Fast Hardener®, 206 Slow Hardener®, 207 Special Clear Hardener® and 209 Extra Slow Hardener® are registered trademarks of Gougeon Brothers, Inc., USA. Diagrams and instructions courtesy of WEST SYSTEM. Manufactured and distributed in Australia by ATL Composites Pty Ltd.
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