DIYbanter - View Single Post - Water-based poly?

wrote:
On 26 Oct 2004 15:26:56 GMT, Gary Fritz wrote:

Gary Fritz wrote:
No matter what the 'purists' say . . . I like water-based poly
for finishing a 'working' surface, like your kitchen table. It's
both hard and relatively impervious to liquids & damage.

Hm. Does it harden as it cures? I just looked at the table and I
can fairly easily scratch/dent the finish with a fingernail. That
would NEVER stand up to my kids.

it takes a while.

there are two things going on. first, the water used as a carrier has
to evaporate. that takes anywhere from a few minutes to an hour or
so. at that point it's dry to the touch, can be sanded and recoated
and the new layer will bond chemically. second, there is a cure
process where the polyurethane/acrylic does it's crosslinking bit
and releases it's primary solvent, usually one of the slower
alcohols. this takes a few days, during which it becomes harder and
more chemically inert. once this is complete new layers no longer
bond chemically, and witness lines and delamination start to become
problems.

[snip]

In my experience it took 7-21 days depending of the humidity, after that
surfaces were as good as pre-poly varnishes.

Josie