ambrosia maple table finish

[charlie spencer]

If I seal a table top with shellac, will lacquer or poly be waterproof and keep the shellac protected?

[Scott Holmes]

The shellac is fine by itself... It does not need poly or lacquer to make it a good vapor barrier.

As for protecting it; you will need to determine what you are protecting it from: shoes, use poly;
writing or eating; use a hard varnish, not a tough varnish.

Waterlox Original or Behlen's Rock Hard Table Top are both excellent phenolic resin varnishes which are much harder than poly. They cost a lot more than poly; they are worth every penny.

If you are using a light colored wood you may be better off with an Alkyd resin varnish, still much harder than poly and it does not yellow much at all and it goes on clear with very little amber. Sherwin Williams Classic Oil Varnish or my fav. Pratt & Lambert #38.

[Casey Gooding]

Unless you have stained the wood, there is no need to shellac before lacquer. If you have stained, there is no need to shellac before poly. In fact, if you do shellac before topcoat, you will weaken the topcoat. Probably not enough to be noticed, though. I don't understand the chemistry in that, but it's what Bob Flexner says.