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J. Clarke[_4_]

In article ,
says...

On Friday, July 31, 2015 at 3:22:48 PM UTC-4, dadiOH wrote:
DerbyDad03 wrote:
On Friday, July 31, 2015 at 10:28:04 AM UTC-4, John McCoy wrote:

If I'm not mistaken, polyurethanes take 100 hours or more to
completely cure. So you should be safe applying a new coat
within that time without sanding, it will chemically bond to
the coat below. Of course, it likely does vary between varnish
types and brands. As Mike says, check the manufacture's
instructions (altho those are probably conservative).

I assume by "conservative" that you mean they probably want you to
wait longer than is actually necessary.

The problem is, the Minwax WOP says to sand it after 2-3 hours. After
2-3 hours, in my experience, the WOP still seems to be too
wet/tacky/sticky (pick a term) to sand. 2-3 hours seems - at least to
me - to be a far cry from conservative.

You've never said whether you are using oil or water base varnish but still
sticky after 2-3 hours would indicate oil, right?

Actually, I never said I was using varnish. I am not. I am using Minwax Wipe On Poly, but yes, it's the oil based version.

Are you leaving a film like you would with brushed on, or are you
rubbing it in? If you're leaving a film, try rubbing it in instead.

If so I don't see
anything wrong, wait until it isn't sticky to sand if you just gotta sand
and that is going to be more that 2-3 hours.

OK, sort of...

It still doesn't make sense to me that the instructions on the Minwax product say to sand in 2-3 hours but no one in the real world agrees with that.

In any case, I should be around this weekend which will give me time to keep an eye on the dry time and apply more coats without the need to sand. Since wipe on poly goes on a lot thinner than brush on, I want to make sure I use enough, especially on the top of the nightstand.

400,000 cycles per month of a cell phone sliding on and off the nightstand will wear down the finish pretty quickly. After all, it is for a college student. ;-)

But if you ARE going to sand, I'd wait longer - at least 24 hours - and if
you are after a baby butt smooth surface, wait two weeks to sand before the
last coat...it takes at least that long for oil poly to cure; if you sand
and recoat before it is totally cured, the thicker layer left in the pores
will continue to cure and shrink and there goes the flawless surface.
__________________________

FWIW, these are my experience with poly...

OIL
The only thing I've used oil poly on for years is my Saltillo tile floor (I
use lacquer or oil on furniture). I have 4000+ sq.ft. of it and
all except baseboards and trim (they are Saltillo too) has 3-4 (I try for
four) coats. It is generally applied ratherheavily...I pour out a line
about 5-6' wide and start pulling it around with a mohair applicator. As
soon as I can walk on it barefoot without sticking, I apply the next coat;
that time is never less that 3 hours, rarely much more that 4.

WATER
I have used it but don't like it. Things covered by it look dull and it
doesn't wear nearly as well as the oil base. I use it to keep a finish as
light as possible or (sometimes) to top coat acrylic "enamel" so stuff
doesn't stick to it. I did use it as an after thought on an oak dining
table; originally, I used BLO but some months later decided I wanted
somethng more durable so wiped on a few coats of water poly. There, it
looks OK because the oil provided color to the wood.

When I wipe it on, one coat follows another in an hour or less.
________________

Apropos to what John said about poly being a mix of poly and acrylic, I
believe that is correct for water base but IIRC the oil base is a mix of
poly and alkyd.