On 12/18/2012 11:52 AM, Greg Guarino wrote:
On 12/18/2012 11:58 AM, Larry Blanchard wrote:
On Tue, 18 Dec 2012 09:19:29 -0500, Baron wrote:

Context:Plywood built-in bookcases.

I assume I should seal all surfaces in some way, even though the top,
bottom, back and one side will never be seen. True? If so, what should
I use? If it simply doesn't matter, I'll probably try to use up some
cans of whatever is on hand.

Shellac.

Dewaxed.

My experience is limited and I don't think I've used shellac since the
jewelry box I made in the 7th grade. (seriously, 1970) It's hard to
remember, and things may have changed. So tell me why I should buy some
for the unseen areas, other than to have yet another thing to finish
test pieces with.

uneven migration of moisture causes warping. the rule is to finish all
sides of everything, including non-visible areas to prevent that.