: When I initially finished my kayak a couple years ago, I was burnt out and
: couldn't face using real varnish and having to wait a day between coats
: and then sand, and then clean up and re-varnish, sand again, etc., so I
: sprayed the bugger with several coats of Minwax Spar Polyurethane clear
: satin and got out paddling.

: Now, I want to brush on several coats of the same poly, but I was under the
: assumption that I could re-coat each hour or two without sanding as I was
: able to do with the spray.

: Upon reading the label, it says to wait 4 hours between coats and then sand
: with 220 grit before applying the next coat.

: What I'm wondering is, if I wait only, say, 2 hours between coats could I
: re-coat without sanding and get a good chemical bond, like we do with
: epoxy that is re-coated within a short time period?

: If the answer is no, you have to sand first, then should I use wet sandpaper
: at 220 grit? Thanks for your help.

Hi Randy,
The answer is no. Varnish uses oxygen to cure fully, adding another coat before slows the curing process. Epoxy cures by chemical reaction, overcoating while fresh allows the chemical reaction to cross link the layers.

Sanding varnish isn't bad, it only needs keying not leveling.
Wet sanding with 220 would work fine, though I dry sand with a light touch, it's easier to see where you've sanded, then I wipe down wet.

Mike Savage
South West Cork