AW Extra 3/14/13 - 11 Tips for Using Epoxy

Follow some basic rules

Epoxy is a two-part glue: a hardener and a resin that combine to form a hard, durable plastic. It’s important to follow the manufacturer’s recommendations and use correct ratios of resin and hardener to ensure the glue cures fully and reaches its maximum strength. Epoxy generates heat as it cures; in fact, the heat helps it cure. The larger the batch, the more heat it generates. It’s best to mix small batches to maximize your working time. If you need a large batch, pour the mixed epoxy into a large flat container, such as a pie pan. This has a cooling effect and increases your working time.

Working with epoxy does require that you take some precautions. Always wear protective clothing and safety glasses when you work with epoxy. Nitrile or Latex gloves are a must. Be sure to work in a wellventilated space or wear a respirator. Be careful to dispose of used rags in a covered metal container.

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Rescue a loose joint

We all have moments when we wish we had left that tenon just a whisker thicker. The gap-filling properties of epoxy make it the perfect solution. Epoxy can fill small and big gaps and still maintain full bonding strength. This is something no other glue or wood filler can match.

Tip: Plastic containers are ideal for mixing, because the epoxy simply peels out after it sets and the container can be reused.

Glue metal to wood

Epoxy bonds many kinds of materials to one another, including wood, metal, fiberglass, masonry, tile, concrete and plaster. It will not, however, bond to most plastics.

Tip: On anodized metal surfaces, such as aluminum T-track, you must sand off the coating before gluing. Epoxy doesn’t stick well to anodized surfaces.

Renew a stripped screw hole

Simply fill the hole with epoxy. When it has cured, predrill for the screws and reinstall the hinge. You can also let the epoxy cure with screws in place for a permanent attachment. If you want to make the screw removable, apply a coating of oil to the threads before pushing the screw into the wet epoxy.

Tip: On a vertical surface, it’s nice to have an epoxy that won’t run. Gel epoxy is the perfect choice. It has a consistency similar to that of petroleum jelly. You can even make your own gel epoxy by adding a thickener.

Make an epoxy inlay

Rout a 1/8-in. x 1/8-in. groove and mask around it with tape. Mix a batch of slow-setting epoxy and add a colorant. Powder tempera paint works well. Add thickener (see Sources, page 26) until the epoxy is the consistency of petroleum jelly. Apply enough epoxy to the groove so it sits slightly above the surface of the wood. After the epoxy sets but is still slightly soft, remove the tape. When the epoxy has fully cured, sand it level.

Use when clamping is awkward

Epoxy forms a mechanical bond and needs only contact pressure to adhere. Use quick-setting epoxy, press the parts into place with your fingers and the job will be done in only a couple of minutes.

Tip: Wood is a porous material that absorbs epoxy. Applying it to both surfaces will ensure that enough is left unabsorbed to bond the two parts together. If you do use clamps, don’t turn them too tight or you will squeeze out too much glue and starve the joint.

Waterproof outdoor projects

When used as an undercoat or sealer, brushable epoxy greatly reduces expansion and contraction in wood. Coat all parts prior to assembly and make sure epoxy gets down into the fastener holes. If the wood absorbs a lot of the epoxy, sand the first coat after it cures and apply a second coat. Epoxy is not UV-resistant, though, so you must topcoat your project with exterior varnish or paint. The extremely stable epoxy base coat also means that your topcoat will last much longer before refinishing is necessary.

Sources

(Note: Product availability and costs are subject to change since original publication date.)

Devcon, devcon.com, 800-933-8266, Fast- and slow-cure and gel epoxies.

Loctite, loctiteproducts.com, 800-321-0253, Fast- and slow-cure and gel epoxies.

Super Glue, pacertech.com, 800-538-3091, Fast- and slow-cure and gel epoxies.

System Three Resins Inc., systemthree.com, 800-333-5514, Fast- and slow-cure and brushable epoxies and fillers.

West System, westsystem.com, 866-937-8797, Fast- and slow-cure and brushable epoxies and fillers.

Zap, pacertech.com, 800-538-3091, Fast- and slow-cure and brushable and gel epoxies.

This story originally appeared in American Woodworker July 2005, issue #115.

July 2005, issue #115

Purchase this back issue.