Robert11 wrote:
Hello:

Saw in HD the other day some 1-1/2 or so laminated, butcher block type,
blocks that would make a really nice table top if stained.

Question: If I use Min-Wax poly on it, or something similar, is it a good
idea, or necessary, to do the underside also ?

While not necessary, it is a good idea.

Why ?

Of every piece that I have repaired or refinished, none have been
finished on the underneath surface. This is the tradition. It may be
desirable, however because it will further protect the wood. One
purpose of the finish is to help prevent the expansion and contraction
of the wood. One must assume that finishing the underneath would
further aid in this goal. If you were making this in a factory or
commercial shop then finishing the underneath would be unlikely. for
your own personal project, it can quite certainly be done. It is quite
a bit of extra trouble, however.

Also: for a "hard" finish as it'll be a desk top, is Min Wax Polyurethane
the best bet, or...

I am not knowledgable in the minute details of different finishes but I
have had good experience with all of the poly finishes.