The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

Chapter 15 – Coating and Finishing 161
Applying Paint and Varnish
We are always reluctant to spray paint or varnish
because of the health hazards involved in the application
method and have usually relied on the roller-brush
method of painting and varnishing. With some experience
and the benefit of a good material, this technique
can rival a quality sprayed finish, but you must develop
your skills. We hope that the following comments will
help. See Chapter 26 for details on applying varnish
and paints to interiors.
Before you begin coating, prepare your final sanded
surface. It must be free of all dust, dirt, sanding residue,
and contaminants. We suggest using a four-step surface
preparation procedure:
1. Wipe down the hull using a large sponge, continually
rinsing it out in a large bucket of water. Try to
keep it as clean as possible as you remove the
majority of the loose material from the hull surface.
2. Wipe the wet hull dry with soft, clean rags or paper
towels.
3. Wipe the hull down again, following the paint
manufacturer’s recommendations for final surface
preparation.
4. If recommended by the paint manufacturer, use a
tack rag to remove any remaining dust or dirt from
the hull surface. (Use a tack rag again just prior to
applying paint to the surface.)
Dust control can sometimes be a difficult problem in a
wooden boatshop. Usually, you should discontinue all
wood sawing or machining operations well in advance
of the actual painting operation. It is a good idea to wet
down the entire boatshop floor with a light spray of
water. This will not only help keep dust down on the
floor, but will also attract dust from the air.
Use the same foam sponge rollers to apply the paint
film that you used to apply WEST SYSTEM epoxy and for
the same reason: control. This type of roller does an
excellent job of applying a controlled film thickness
over a large area in a minimum amount of time.
<strong>The</strong> primary uses of a brush are to smooth out the
stipple finish which the roller leaves and to paint those
areas that are difficult for the roller to reach. Even application
of paint to a surface is difficult with a brush
because of the problem of controlling the film thickness.
<strong>The</strong> painting job is best split up between two people,
and this is without question the fastest method. Arm
one person with a roller and roller pan and the other
with a 3" or 4" (75mm or 100mm) wide brush and a
small container of paint. <strong>The</strong> “roller” begins application
of the paint, using long, steady strokes to cover a
specific area before the roller is again filled in the paint
tray. It is important to learn early the approximate
surface area you can cover with a roller full of paint as
you apply it to the hull surface. Once you have developed
a feel for “area,” you will be able to plan the
rolling application better. <strong>The</strong>n you won’t get in trouble
with too much paint collected in a given area and no
place to move it to. A common error is to discover that
you are a little light on paint film in one area, but in
correcting the situation you make it much worse by
applying much more paint than the area can handle
without running. <strong>The</strong> solution is to learn how to get
just a little paint out of the roller pan with the roller,
just as you might control the amount of paint on a
paint brush by scraping it against the sides of a paint
can. It’s harder to do with the roller, but can be done.
Immediately after the paint is rolled on, the “brush
person” follows with a slightly wet-out brush, stroking
the surface vertically or horizontally with only enough
pressure to smooth the coating. Finer brushes will
produce the smoothest surfaces with the best chance for
flow out, and we suggest that you use only high-quality
brushes. <strong>The</strong> “brusher” should follow the “roller” as
closely as possible without getting in his way, so that
the time span from initial roller application to final
brushing is as short as possible. This gives the paint
film the best chance to flow out before the solvent
content of the paint film begins to evaporate. For best
results, always finish your brush stroke in the previously
applied “wet” paint area.
Paints are usually composed of 40% to 60% solvents,
most of which will evaporate before the paint film
cures. <strong>The</strong>se solvents play a key role in the successful
development of the surface finish. Immediately after
you apply paint to a surface, the solvents it contains
will begin to evaporate, and a cure or drying out of the
paint film begins. <strong>The</strong> rate at which the solvents evaporate
is crucial to the roller-brush application process. If
the solvents evaporate too fast, the paint film will not
have a chance to flow out smoothly. Brush or roller
marks will remain visible. If too much solvent is used,