"bent" wrote:

Is there a good chemical for helping to remove a few layers of
Minwax
Helmsman Spar Urethane clear Satin finish that may be one to several
years
old.
snip

Your basic paint remover is basically Sodium Hydroxide (Noah) AKA:
"Caustic", with an inert carrier.

It should be neutralized when finished with acid, usually phosphoric,
and finally water..

If you not careful, caustic will soften the pulpy part of the wood
being cleaned. Don't leave on and forget about it.

I'd start with so 60 grit to cut thru the dirt and the bulk of the
varnish, then use NaOH.

The commercial paint removers will have a carrier to hold them in
place.

Apply with a chip brush.

BTW, SFWIW, acetone is probably the most powerful of all the keytones.

Lew