yoga92829

Epoxies have a wide acceptance in the marine industry, but they haven't caught on in the wood shop as well as they should. Having been associated with the marine industry myself and with the use of epoxies for many years, I have developed a good working relationship with epoxies, and I use them quite often in place of other adhesives, especially when high strength and moisture resistance are factors.

To properly use epoxy, one must first understand the basics. Epoxy is a two part adhesive consisting of a resin and a hardener, and is primarily divided into two classes: quick-set and slow-set. They are further divided within these categories by the mixing ratios, which are designed by the manufacturer. They can be anything from 1:1 to as much as 16:1, depending on curing time, viscosity, ultimate strength and intended use.

Quick-sets are usually 1:1 by volume, so that equal amounts are squeezed from hypodermic-like syringes and mixed to a uniform color and consistency. They usually achieve their strength in 10 minutes or less, and a full cure within 24 hours, but they rarely reach the high strength that the slow sets do, and quite often retain some flexibility and resilience.

Slow-sets allow more open or working time, and can take up to 24 hours to cure. The advantages are superior strength, water resistance and gap filling capability. They don't take as much clamping pressure as other adhesives, and I have had success with only contact pressure. As a matter of fact, too much clamping pressure can force the epoxy out of the joint resulting in a lean or starved joint.

The gap filling capability is no excuse for poor workmanship, but if a mistake is made, epoxy can be very forgiving. The viscosity can be altered very easily by the addition of fillers such as sawdust, wood flour, talc, or colloidal silica. I use a product called "cabocil", which I get from my epoxy manufacturer, and in fact many epoxies are pre-filled with cabocil to moderate the consistency. In an emergency repair, I have even used copper wool as reinforcement, along with the cabocil, allowing a boat owner to get to his home port before making the permanent repair.

Epoxy cures through an exothermic polymerization, or heat producing chemical reaction in which there is very little moisture loss, resulting in less than 0.05% shrinkage, the main reason that epoxy is such a great gap filler.

Probably the greatest advantage in using epoxy is the ability to join dissimilar materials. The adhesion factor is as great on metal as it is on wood, but some non-porous materials need to be roughed up to enhance the bond.

Each manufacturer has his own specifications for mixing and using epoxy, and the instructions need to be followed closely. Too much or too little hardener can result in a gooey mess that never will cure.

Storage instructions must be followed also. Some hardeners will harden from exposure to air, and water in either resin or hardener is a definite taboo. When using epoxy that is approaching the limits of it's shelf life, the resin and the hardener should be stirred thoroughly prior to mixing together. If crystals have formed in the hardener, you can sometimes restore it by immersing the container in warm water to heat the hardener enough to dissolve the crystals.

Care must be taken to avoid excessive heat and contamination of the product with water. Stir the hardener to restore the consistency.

At as much as $50.00 per gallon, epoxies can be expensive, and because of limited shelf life, don't buy larger quantities than can be used in the recommended time frame.

Most epoxies are formulated for use in moderate weather conditions, between 50 and 90 degrees Fahrenheit. Cooler temperatures slow the curing time and warmer temperatures will accelerate it. This can be used to advantage by refrigerating the mixture to prolong pot life, or by warming the mixture to speed up the cure.

Depending on the use, application can be by roller, spray gun, trowel, or putty knife. Some are thin enough to be injected into joints with a hypodermic syringe. Clean up can be done with soap and warm water if done soon enough, or with acetone, lacquer thinner, or denatured alcohol. If using a spray gun, spray plenty of solvent through the gun to assure the complete flushing of the equipment. For safety and environmental reasons, spray the solvent into a container for proper disposal.

I am a retired professional woodworker with over 50 years experience in virtually all phases of the construction industry. I would like to pass on a few of the tips and tricks that I have learned through the years. I have written a few e-books on diverse subjects related to woodworking and construction, and am adding more all the time. Visit my store on eBay to see my books: I am now offering a limited selection of epoxies in my eBay store at: http://tinyurl.com/3chxox