Greg Guarino wrote in
:

4.The timing.

The online instructions say to wait 4-6 hours between coats. So again,
what happens if we don't wait long enough, "long enough" perhaps being
lengthened by the ambient temperature during the first hour outside?
Does the second coat prevent enough oxygen from getting to the first
coat, perhaps?

Like you, finishing isn't really my strong suit. But my
understanding is that, if you recoat too soon, you're basically
just creating one very thick coat. Since the solvent has to
evaporate, and that happens very slowly once a skin forms on
the finish, very thick coats are not recommended...

(I note that professional finishers often spray on coats on a
much shorter schedule than 4-6 hours. But they're spraying, so
a much thinner coat to start with).

Perhaps, given the apartment setting and his infant son, a water-borne
poly would have been a good choice. I thought I read somewhere that
despite being *carried* by water, the poly is still poly.

Water-borne poly is just that, regular poly carried by water.
To be specific, it's regular poly in an emulsion in water.
Once the water evaporates, you're left with the normal poly
solvents (just much less of them).

The only non-hazardous finish that comes to mind is shellac.
But as someone pointed out (and I'd forgotten), that's not
such a good choice with the heat from the radiator.

John