Greetings Mash3! Painting over shellac can be accomplished
successfully but I would suggest lightly sanding the shellaced areas
with a fine sandpaper (220 would work well) and then priming the wood
before painting over it. This process will take longer but will
ensure a uniform surface.
After choosing the color of your paint, have the paint shop add that
color to your primer. This produces a much better end result. I
recently painted my kitchen - I painted over wallpaper. The paper
couldn't be successfully removed because it had been directly placed
onto the sheetrock with no sizing underneath. To remove it would have
brought pieces of the sheetrock off with the paper. I painted the
kitchen a deep red so I had the paint shop add the red pigment to my
can of primer. The primed surface was so easy to paint over!
Painting over shellac will sometimes cause flashing which are shiny
spots unlike the rest of the painted surface. However, "this problem
will correct itself in a few days. The shellac seals the surface which
causes the paint film on top of it to dry very slowly. You will have
shiny spots for a few days or for however long it takes the paint to
dry." This advice is from
http://www.netpei.com/carvells/html/flash.html. They also suggest
that if you miss a spot during painting, do not go back and fill it
until the paint has dried. I can concur with this because when I have
done that, the drying paint is sticky and reapplying the paint when
it's partially dry will cause the brush to remove some of the already
drying paint.
As for the difference between water- and oil-based paints, oil-based
is much more hardy and sturdy for surface cleaning. Many people
choose oil-based enamel to paint baseboards, kitchen cabinets and
heavy work area cabinets and surfaces. However, oil-based enamels
require cleaning brushes with paint thinners as opposed to just
washing them in water.
From http://www.servicemagic.com/painting_and_staining/paint_preparation.html:
"The vast majority of finishes used today are water-based latex. Oil
based paints are rarely used for finishes anymore because the
Environmental Protection Agency (EPA) has put a limit on the amount of
volatile chemicals that can be used.
"The first thing to understand is that paints have different gloss
ratings (or sheens), from flat to lo-sheen, eggshell, semi-gloss and
finally, gloss. Flat has little or no sheen and is used primarily for
walls and ceilings. The remaining are considered enamels and can range
from a five to 85 percent sheen rating – the higher the rating, the
higher the shine. These are used for trim, cabinets and walls in
kitchens, bathrooms and laundry rooms. Many homeowners use enamels on
all their walls because they are more durable and easier to clean, but
I recommend lo-sheen because it is more attractive than shinier
enamels."
Another reason to use a lo-sheen paint is because the shinier the
paint, the more imperfections will be noticed on the painted area.
Because your surface is pine boards, you might consider a lo-sheen so
that the knot areas will not be prominent after painting.
You didn't specify whether or not the boards were on a floor on on a
wall. If they are floor boards, I would recommend you use an
oil-based paint because it would be the most durable. Then you could
choose to seal over the paint with a thin coat of polyurethane to
futher protect the painted surface. If you are painting wall boards,
I would recommend latex (water-based) paint.
Should you need clarification of any of the information I have
provided, please request a clarification and I will be happy to
conduct further research.
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