Applying Finishes Over Epoxy Coated Surfaces

by Glen-L Marine Designs

As a general rule, we advise against spray application of paint systems unless already an expert and has the proper facilities to assure sound, safe results. With a good paint system, properly applied, excellent results are possible by the amateur without using spraying methods (rollers and brushes work well with many systems).

Some builders ask the question about pigmenting one or all of the various coats of POXY-SHIELD® used with the GLEN-L Epoxy Encapsulation System. Pigments should not be used with the first coat as this can effect penetration ability. Pigmenting of the resin is optional and has drawbacks as well as a couple of advantages. Any pigment used must be compatible with epoxy resins. Pigmenting may increase the viscosity of the resin so don't add more than about 2% by volume. The depth and intensity of most pigments are not enough to eliminate the need for paints which have much higher pigment content. Also, pigments may decrease the resin's moisture absorbing resistance. The addition of pigments will not make resin into a paint; it will still need to be sanded, sometimes resulting in an uneven color.

Adding pigments can serve as a guide when sanding a coat of resin, since over-sanded areas turn lighter indicating that no more sanding should be done in that area. Pigments also allow visual control of the coating thickness being applied. Pigments can also be added to the final coating to match the color of the final paint system, giving a pre-colored paint base perhaps eliminating the need for undercoats. In short, pigments can be used, but they are far from a necessity, and will not eliminate the need for a final paint coating.

Before doing any finish work or applying finishes, allow the last coat of epoxy to cure 5 to 7 days at 70 degrees F, longer at colder temperatures. Wipe down the hull with a water/ammonia dampened rag or sponge. This will eliminate the greasy feeling amine blush to make final finish sanding easier and minimize clogging of the abrasive.

lf you have been careful in your application of resin with all coats, making sure each is evenly applied, and have taken care to prevent runs and sags, and to correct mistakes along the way, the finishing process should be relatively easy. Final finish work will vary depending on the quality of surface which is desired, whether the surface will be naturally finished or painted, and whether or not a sanding undercoat will be used.

Final finish sanding is usually done with either an orbital sander or hand sanding block. lf you wish to use a disc sander, equip it with one of the foam backing disc pads which will minimize gouges. lf you have not used a disc sander, some practice may be in order since these can easily damage a surface. The rpm of the disc sander should be kept relatively low (around 2000 rpm) since it is possible to scorch the resin surface if rpm's are too high.

Start out sanding with a 60 to 80 grit open coat paper, advancing to a 120 to 180 grit. For many builders, this will yield good enough results for painting, but for a high-gloss natural finish, work up through finer grits as required, ending off with a 220 to 280 or even finer grit wet-or-dry paper using wet sanding techniques. Be careful not to remove too much resin by sanding, and if it looks as though too much sanding will have to be done, it may be better to apply more coats of POXY-SHIELD®.

Note that POXY-SHIELD® will not in itself provide a perfect "bar top" finish, even when flow coating. Although the epoxy has high gloss properties, it is not a final finish. An ultimate final high-gloss brightwork finish is best achieved through finish sanding and coating with varnish or comparable clear coating products, and such is required for all exterior use for U-V protection.

lf using varnish, apply at least two coats (more is usually better) of a U-V stabilized varnish or clear polyurethane product. lf your surfaces are to be naturally finished, it is preferred to use only Fast hardener for all coats for a faster cure and better long-term clarity. lf the resin cures more slowly, such as with the use of the Slow hardeners, a potential exists for clouding of the clear coating in the presence of moisture.

CLEAN UP, SOLVENTS, & THINNERS

Epoxy resin products can be messy and get on surfaces where they are not wanted. They should be removed before they cure to avoid having to grind them away later. This is especially important when gluing around interior areas or on surfaces where visual appearance will be important. While the resin should be cleaned up before it cures, there is no particular rush to remove immediately as it exudes from a joint. In fact, as it stiffens up a bit, removal is actually easier since there won't be as great a tendency to spread it around while it is still fluid, especially the with POXY-SHIELD® due to its thinner viscosity. However, don't wait too long or the resin will cure hard. Nothing can remove the resin at this point other than sanding.

Excess resin can be removed with thin sticks of wood, putty knives, or similar tools. Don't let the uncured epoxy fall to the ground or floor where it will stick to anything and everything or get tracked around; scrape it off into a container. Then wipe surfaces that are to be cleaned using a lint-free rag soaked with a proper solvent.

DENATURED ALCOHOL is the best and probably the safest solvent from a bodily contact standpoint (although it is flammable). Ordinary mineral spirits (paint thinner) is also relatively safe. Other solvents are more hazardous, from a vapor inhalation and/or flammability standpoint, as well as from long-term health affects.

ACETONE is a very effective solvent but has a relatively high evaporation rate, making it necessary to keep the container closed at all times when not in use for safety and economy. The main problem with acetone is that it is highly flammable. Any wood boatbuilding situation offers the potential of a fire hazard, and therefore fire safety is always important.

LAQUER THINNERS are a generic group of solvents which function similarly to acetone, however, there are different formulations. Fumes are also easily detectable in most, but they are not quite as volatile as acetone, yet still considered highly flammable.

TOLUENE, a common constituent of lacquer thinners, is not quite as flammable as acetone nor as volatile, but can reach anesthetic affects at much lower levels. A 50/50 mix of toluene and acetone is sometimes used as a solvent to moderate the qualities of each.

Just about all solvents are dangerous products from one or more respects, and costly. Skin contact should be avoided, especially when working around epoxy products. Most of these products tend to open the skin pores and remove protective skin oils, driving both the solvents and the resin more deeply into the skin and perhaps ultimately into the system of the user. The results are a much greater risk of skin reactions of greater severity.

For personal clean-up of uncured resin from skin, ordinary water and soaps or detergents (including ammonia), or denatured alcohol can be used. However, we prefer the use of waterless hand cleaner products which are specifically intended for use with resin products. These usually have added protective oils that keep the resin from being absorbed by the skin and don't tend to dry the skin. Of course, personal clean-up is much easier if barrier cream has been applied-and protective clothing and gloves worn.

Again it should be emphasized that neither POXY-SHIELD® or POXY-GRIP® products should be thinned with solvents or thinners. This will distort and adversely affect the properties of the resin, perhaps to the point where they simply will not work.

Editor's Note: Glen-L now can supply you with "Water-Based Marine Paint For a Professional Finish That Will Knock Your Socks Off!"

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