I thought I would share this. 5 years ago I finished a mahogany transom
with minwax ipswitch pine and then topcoated with polycyclic. For some
reason it has held up well. Even though it is sold as an interior
product. Wood that got the polycrylic without the stain shed the
polycrylic in a couple of years and the wood turned grey.
Could the answer be the stain sealing the wood which allowed the
polycrylic to stay on the wood?
I came across this posting and he appears to have some similar
experience.
http://groups.google.com/group/rec.woodworking/browse_frm/thread/f9bc391afa2b325c/d2cce9aecda368a1?lnk=st&q=polycrylic+minwax+exterior&rnum=3&hl=en#d2cce9aecda368a1
'The plywood dart-board cabinet puzzles me. I painted the back with
exterior latex. Then, I applied a few coats of clear Minwax
Polycrylic (water-based *interior* finish). The Minwax label said not
to do this. Don't ask me why I did it -- just a crazy afternoon
playing with the chemistry set, I reckon. Anyway, after six years of
brutal Florida sun, rain, storms, hurricanes, humidity, etc., etc. --
that Polycrylic film looks brand new! I have no idea why; I had no
right to expect that kind of performance. But there it is. Go
figger. '
sdowney1 wrote:
> I thought I would share this. 5 years ago I finished a mahogany transom
> with minwax ipswitch pine and then topcoated with polycyclic. For some
> reason it has held up well. Even though it is sold as an interior
> product. Wood that got the polycrylic without the stain shed the
> polycrylic in a couple of years and the wood turned grey.
> Could the answer be the stain sealing the wood which allowed the
> polycrylic to stay on the wood?
I don't know if this is relevant in this particular situation or not.
But when we stain a door, we stain it as opaque as possible to keep the
UV off the wood. ALL clear exterior finishes are problematic when used
alone, and much research by (not sure it was them) the Thermatru
corporation as well as others has proven that there is much less damage
to the wood when UV is blocked, not just mitigated. Uv damaged wood
dries out faster, shrinks, and moves which destroys the top coat. As
the top coat gets older and more brittle, it is less elastic and starts
to break down with movement.
Bearing this out, doors we have stained an opaque color and finished
last much better than the ones we just put a toner in the finish and
apply.
Robert
sdowney1 wrote:
> I thought I would share this. 5 years ago I finished a mahogany transom
> with minwax ipswitch pine and then topcoated with polycyclic. For some
> reason it has held up well.
At a guess, your 'ipswitch pine' was a penetrating oil stain, and even
mahogany
can weather a bit better when oiled. Minor porosity in the varnish
would allow some
moisture in, and the oiled wood sheds that small amount of water while
un-oiled
wood might soak some up. The wet/dry/wet/freeze cycling can open up
major
cracks in the wood, and cause it to shed a finish.
Spar varnish (real spar varnish, intended for real spars back before
polymer science...)
was extra oily and gummy (and never really dried out). Folk who tried
it on indoor furniture
found it stuck to clothing... you may have replicated its virtues
without the drawbacks,
by doing those two layers of finish.