Working with epoxy

Along with these safety rules, there are several gluing techniques that will make epoxy a much stronger adhesive.

- Make sure that the surfaces you want to glue together are clean and free from contaminants. Sand them if needed to take off any surface dirt or unevenness. The surfaces don't have to be mirror smooth, in fact a little roughness, or "tooth", will make the bond stronger.
- When cured, some epoxy can be covered with an oily film called an amine blush that is a by-product of the chemical reaction. If left on the surface it can cause some paints to cure incompletely, and may weaken the bond between coats of epoxy. Read the information that comes with your epoxy for instructions on removing it.
- Mix the two parts of the epoxy thoroughly and in the proper ratio. Watch the epoxy when it comes out of the pumps to make sure they are working correctly. If it doesn't look like the proper ratio, stop and check it out. Always use a clean mixing cup, and scrape the sides of the mixing cup with your stick as you stir to make sure that the epoxy is mixed completely.
- Before you add any thickener to the epoxy mixture, brush a coat of the mixed, unthickened epoxy on both parts to be glued, particularly on plywood. This keeps the wood from absorbing too much of the epoxy out of the thickened mixture, causing a "glue starved" joint. Wait a few minutes and if it is all absorbed into the wood, brush on another coat.
- Stir in any required filler after the epoxy is thoroughly mixed. Add a little filler at a time and mix completely before adding more . Be careful when you are stirring to avoid getting the filler stirred into the air. To make an adhesive mixture, mix in filler until it is thick enogh to stay in place when you spread it. You don't want it to drip or sag, but you also want it to flow and fill any gaps in your glue joint.
- There are many types of thickeners that are used with epoxy resins. Some are quite low-tech, such as wood flour (fine sawdust) and milled cotton fibers, and others, like microballoons and graphite powder, make adhesive mixtures with specific properties. It is important to pick the right filler for your needs; high strength, easy sanding, pleasing color, etc. After you are finished gluing, however, don't forget that it is always easier to scrape off any excess epoxy mixture before it cures than to sand it off afterwards.
- Lastly, use unthickened epoxy to seal any area that water might soak into, especially any plywood edges. If the plywood edges are not sealed thoroughly, water will get between the layers of the plywood , causing swelling and delamination. After all the plywood edges are trimmed and sanded, brush on unthickened epoxy until the edges won't absorb any more.

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