| Epoxies have a wide acceptance in the marine | | | | reaction in which there is very little |
| industry, but they haven't caught on in the | | | | moisture loss, resulting in less than 0.05% |
| wood shop as well as they should. Having been | | | | shrinkage, the main reason that epoxy is such |
| associated with the marine industry myself | | | | a great gap filler. |
| and with the use of epoxies for many years, I | | | | |
| have developed a good working relationship | | | | Probably the greatest advantage in using |
| with epoxies, and I use them quite often in | | | | epoxy is the ability to join dissimilar |
| place of other adhesives, especially when | | | | materials. The adhesion factor is as great on |
| high strength and moisture resistance are | | | | metal as it is on wood, but some non-porous |
| factors. | | | | materials need to be roughed up to enhance |
| | | | the bond. |
| To properly use epoxy, one must first | | | | |
| understand the basics. Epoxy is a two part | | | | Each manufacturer has his own specifications |
| adhesive consisting of a resin and a | | | | for mixing and using epoxy, and the |
| hardener, and is primarily divided into two | | | | instructions need to be followed closely. Too |
| classes: quick-set and slow-set. They are | | | | much or too little hardener can result in a |
| further divided within these categories by | | | | gooey mess that never will cure. |
| the mixing ratios, which are designed by the | | | | |
| manufacturer. They can be anything from 1:1 | | | | Storage instructions must be followed also. |
| to as much as 16:1, depending on curing time, | | | | Some hardeners will harden from exposure to |
| viscosity, ultimate strength and intended | | | | air, and water in either resin or hardener is |
| use. | | | | a definite taboo. When using epoxy that is |
| | | | approaching the limits of it's shelf life, |
| Quick-sets are usually 1:1 by volume, so that | | | | the resin and the hardener should be stirred |
| equal amounts are squeezed from | | | | thoroughly prior to mixing together. If |
| hypodermic-like syringes and mixed to a | | | | crystals have formed in the hardener, you can |
| uniform color and consistency. They usually | | | | sometimes restore it by immersing the |
| achieve their strength in 10 minutes or less, | | | | container in warm water to heat the hardener |
| and a full cure within 24 hours, but they | | | | enough to dissolve the crystals. |
| rarely reach the high strength that the slow | | | | |
| sets do, and quite often retain some | | | | Care must be taken to avoid excessive heat |
| flexibility and resilience. | | | | and contamination of the product with water. |
| | | | Stir the hardener to restore the consistency. |
| Slow-sets allow more open or working time, | | | | |
| and can take up to 24 hours to cure. The | | | | At as much as $50.00 per gallon, epoxies can |
| advantages are superior strength, water | | | | be expensive, and because of limited shelf |
| resistance and gap filling capability. They | | | | life, don't buy larger quantities than can be |
| don't take as much clamping pressure as other | | | | used in the recommended time frame. |
| adhesives, and I have had success with only | | | | |
| contact pressure. As a matter of fact, too | | | | Most epoxies are formulated for use in |
| much clamping pressure can force the epoxy | | | | moderate weather conditions, between 50 and |
| out of the joint resulting in a lean or | | | | 90 degrees Fahrenheit. Cooler temperatures |
| starved joint. | | | | slow the curing time and warmer temperatures |
| | | | will accelerate it. This can be used to |
| The gap filling capability is no excuse for | | | | advantage by refrigerating the mixture to |
| poor workmanship, but if a mistake is made, | | | | prolong pot life, or by warming the mixture |
| epoxy can be very forgiving. The viscosity | | | | to speed up the cure. |
| can be altered very easily by the addition of | | | | |
| fillers such as sawdust, wood flour, talc, or | | | | Depending on the use, application can be by |
| colloidal silica. I use a product called | | | | roller, spray gun, trowel, or putty knife. |
| "cabocil", which I get from my epoxy | | | | Some are thin enough to be injected into |
| manufacturer, and in fact many epoxies are | | | | joints with a hypodermic syringe. Clean up |
| pre-filled with cabocil to moderate the | | | | can be done with soap and warm water if done |
| consistency. In an emergency repair, I have | | | | soon enough, or with acetone, lacquer |
| even used copper wool as reinforcement, along | | | | thinner, or denatured alcohol. If using a |
| with the cabocil, allowing a boat owner to | | | | spray gun, spray plenty of solvent through |
| get to his home port before making the | | | | the gun to assure the complete flushing of |
| permanent repair. | | | | the equipment. For safety and environmental |
| | | | reasons, spray the solvent into a container |
| Epoxy cures through an exothermic | | | | for proper disposal. |
| polymerization, or heat producing chemical | | | | |