Working With Epoxy - Part 1 of 3

by Morten Olesen

Often messy and sometimes complicated, working with epoxy can be one of the most difficult parts of bringing your boat plans into reality. Especially for beginners, learning a few basics of working with epoxy can help avoid many struggles and mistakes. In the first of this three-part series, we'll discuss cautions you need to be aware of, as well as the three stages of epoxy. In part two, we'll cover epoxy techniques and in part three we'll do some epoxy troubleshooting.

Take Caution

The first rule of working the epoxy is to avoid skin contact with uncured material. If you've ever seen hardened epoxy, you can just imagine how dangerous this substance can be if it touches and/or hardens on your skin. This hazard is greatly reduced as the epoxy cures, but is still present when sanding partially cured epoxy. Wear protective gloves, clothing and glasses. Never use solvents to remove epoxy from your skin. You'll want to have on hand a special resin-removing cream for this purpose.

Always use ample ventilation when working with epoxy. You don't want to breathe vapors or sanding dust.

One trick is to use sand or clay cat litter to absorb spilled epoxy. However, take note to never use sawdust or similar materials for spills as spontaneous combustion can occur. Also, according to West Systems, manufacturers of epoxy products, "Large volumes of curing epoxy can become hot enough to ignite surrounding combustible materials and produce hazardous fumes. Place containers of mixed epoxy in a safe and ventilated area away from workers and combustible materials. Dispose of the solid mass when the cure is complete and the mass has cooled."

Three Stages of Epoxy

Hardener cure speed, epoxy temperature and the volume of epoxy mixed will all contribute to the overall open time (time available for mixing, applying, smoothing and shaping) and cure time. In warmer conditions, use a slower hardener mixed in smaller batches to increase your open time. You can even get extra-slow hardeners so you can work with epoxy in temperatures as high as 110 F (43°C). In cooler conditions, use a faster hardener or a heat lamp to speed up curing. NOTE: If you use a heat source, do so carefully, as too much heat can melt the epoxy causing it to run or in the worst case spontaneously combust.

From the time epoxy is mixed until it hardens fast, epoxy goes through three stages.

1. Liquid (Open Time) - During the open time (also called working time), epoxy is suitable for application. All assembly should take place during the liquid phase to achieve the strongest bond.

2. Gel - As the epoxy begins to cure (the "green phase" or "cure phase") it becomes no longer pliable. If the epoxy is still tacky, you can still bond additional epoxy to it. At this phase dry sanding is not possible.

3. Solid - During the final cure phase, the epoxy becomes a hard solid. It can now be dry sanded and shaped.

The process can go quickly depending on temperature and other factors, so you'll want to have everything you need readily available. It is also wise to have conducted a test run or to have mentally reviewed the process you'll follow before beginning to mix your epoxy. This is especially true for first-time users.

It is advisable to have the following available:

· Protective gloves, clothing and glasses

· Epoxy (Resin)

· Hardener

· Fillers (Thickeners)

· Plastic or metal cups or containers (do not use paper or Styrofoam)

· Wooden or plastic spoons or spatulas

Understanding the basics always helps to ensure a smoother start to any project involving boat plans. Practice with scrap materials until you are confident in your ability to carefully and quickly work with epoxy. When you're ready, you can move forward in developing proper epoxy techniques.

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