there are many things that are "varnish". Polyurethane is AN example of
varnish. Varnish, in general, is simply a mixture of oil and resin. In
that article he talks about using a "short oil varnish" (IIRC). This type
of mixture is (obviously) a greater percentage of resin vs. oil, so it cures
harder. The type of oil and type of resin are important, and that's why
there are so many types of varnish out there. In that article, he used a
varnish with an alkyd resin. This differs from others using phenolic resin.
Polyurethane varnish is made with (you guessed it) polyurethane resin (and
usually, i think, is mixed in some part with alkyd resin).
Various properties vary, such as bonding propeties, cured appearance (hence
the boloney out there about polyurethane looking like plastic - it's
possible, but not a definitive property), yellowing character, etc.
In short, the varnish in that article was a short-oil alkyd varnish, so, no,
it wasn't polyurethane.
That's a good question, and one I'm afraid I don't know. I haven't ever
used an alkyd varnish myself. That article had a can of one showing, did
you search on that name (I don't have the article in front me, so I don't
remember what it was). I'm sure someone here can tell you.
By the way, I found this article which might prove helpful to you as well:
I found this one:
look at the "Old Masters Super Varnish" towards the bottom of the page.
Honestly, as long as you don't get a spar varnish, and let the varnish cure
sufficiently (I'd say at least a week if not two), then you should be ok for
indoor use. The resin type is probably less important. If you want a
really hard surface, try a rockhard tabletop finish - most of which I've
seen are polyurethane varnishes. As always, you need to experiment with the
specific products you have in your hands and see how the finish looks to you
on the items you're working on.
Thanks for the info Mike, finishing is where I'm still experimenting and
learning. I've been woodworking for about 3 yrs. and finally getting the
shop set up with decent tools. I've used poly, wipe on poly, shellac and
several others including Waterlox finish. I started out using cheap pine,
then the pondorosa pine which is a little better and now that I have a
planer and jointer I'm getting into the hardwoods. Projects I'm working on
now are red oak.
Again thanks and have a great weekend.
Most varnishes in the home centers / paint stores today are alkyld, or, as
pointed out above, an alkyld - poly blend. Very few have any phenolic
resins in them, and those tend to be marine. For a few years now, the CAS
numbers of the produc's components have been listed on the labels, and they
will call out the different resins, sometimes more than one of the same type
(for instance, two different CAS numbers for alkyld resins). The natural
resins tend to remain slightly soft - as a matter of fact, the Epifanes guys
(best marine varnish in the world, IMHO) like to say that a natural resin
film isn't completely cured until it's peeling off. Polys on the other hand
do get hard, which makes them attractive for high-abuse areas: floors and
Varnishing red oak can be a real pain, because of the very open pores. I
recently went through the exercise with a couple truck loads of 8/4 edge
glued red oak table tops for a restaurant/bar. Without some sort of
filler/sealer, the pores just will not build a film and give you a smooth
surface. (Six coats later, they were still absorbing finish.) Also,
without a sealer, pinholing of the finish over the pores can be an issue.
(As I understand this issue, the pores suck in finsih and the evaporating
solvent creates a bubble and then a pinhole as it escapes).
Yes, we stained the tops with a witches' brew, then sealed and varnished.
The sanding sealer was made by the varnish manufaturer. After some hours on
the phone with our varnish manufactuer's tech guys, this is what I can
-- Compatibility is guaranteed only by testing.
-- With the advent of the low VOC regulations and the consequent product
reformulations, manufacturers test for compatibility only within a narrow
spectrum of products, typically their own. So, if you're doing what we did,
which was stain with Minwax and varnish with McCloskey, caveat emptor. (We
now use SolarLux stains and dyes, no longer Minwax. That job was an
interior renovation, so we had to match the existing colors and didn't have
time to develop new formulas with different products.)
-- Talk to the manufacturer's tech support. They are (usually) happy to
help you head off problems rather than deal with them afterwards.
-- Compatibility is guaranteed only by testing.
I took a finishing class taught by a guy with 20 something years as a
finishing products sales engineer. Part of his job during that time
was to help his customers, which were cabinet and furniture shops,
rather than retail customers, figure out what went wrong.
He emphasized "systemizing" with finishing products. In other words,
use one manufacturer's products from start to finish, whenever
possible. He never talked WHICH manufacturer, he encouraged us to
make our own decisions.
If a systemizing wasn't possible, just as Tim mentions above,
thoroughly test it first! Another point the instructor mentioned was
that the best tests have some time after them, before declaring the
test a success. He mentioned seeing combos that seemed OK for a day
or two, only to fail a week or two, or even longer down the road, as
one of the components finished curing.
Why does everyone and their copulatin' brother want a SMOOTH
finish on a nicely textured wood? Why don't you all just use
a smooth, closed-pore wood if you want a copulatin' mirror?
There. I feel better. (Sorry, Tim.)
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Well, sometimes you want to know that the wood's pores are not sucking in
oil from spilled french fries, or milk shakes, or coffee, etc. What's the
real risk? Low, probably, but you're not the one who has to convince the
Health Department inspectors when they come to renew the yearly license.
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