Some years ago I built a couple of two-tier tables out of pine. It was
my intention to paint them gloss white, but before I did so a house-mate
asked me, "why paint them?" I had no answer and never did paint them. In
fact, as I'd constructed them I filled in blemishes with fillers that
are somewhat unsightly, so in that respect I suppose the pieces do beg
for paint. Maybe someday.
Last year I constructed 3 large pine bookcases, and I again could have
left them unfinished but I instead decided to finish them. I did a fair
amount of research and decided on shellac. Actually, I'd gotten the idea
from a fellow in a store that sold pine bookcases (unfinished). He
recommended a white shellac, and I believe he was referring to a shellac
that when dry looks like white paint (has white pigmentation). Shellac
has the virtue of sealing effectively, so that resins do not exude from
knots, eventually spoiling the finish.
I did further research before embarking on the project. I decided to
finish the wood prior to assembling the bookcases (after cutting and
sanding however). I also decided to do a preconditioning with boiled
linseed oil - wipe on, let sit 15 minutes, wipe off thoroughly with
rags, and let sit for several days or a week or more to cure (dry to the
touch). This was said to accentuate the grain for a more pleasing effect
I chose an orange shellac and applied two full coats after a thinned
(with alcohol) shellac initial coat.
Lastly, a couple of applications of furniture wax with 00 steel wool,
followed by polishing with rags, gave a fine furniture look and feel.
I'm very pleased with the warm look of the finished bookcases, which I
just finished installing in their final location yesterday.
You may not want to do something like this if you are antsy to get these
installed, and I figure you probably are. Anyway, maybe you are
completely OK not finished them at all! :) I don't believe that it's
"necessary," and that was your question.