Refinishing old table for MIL. Table is small coffee table made of white
hard wood with walnut veneer on top everything stained with a med dark
stain. Cleaned the table with denatured alcohol and cleaned up 80% of finish
problems, on top used a finish remover, sanded, cleaned with denatured
alcohol. sprayed on water based poly this afternoon and the table has
turned white, looks like a poor paint job. Sprayed box made of oak and
maple yesterday and it looks good, same can of finish, Finish has been on
table about 5 hours and is still tacky, temp is 70 deg F and falling,
humidity is 79% with rain coming in. any suggestions on what went wrong (my
fault I'm sure) and what corrective measures to take.
You will get a lot of opinions here, so here's mine. You have some
contamination that has worked its way under your poly that isn't
You may have loosened up or dissolved some of the old finish when you
cleaned the surface with the alcohol and it remains on the top (under
your finish). There may have been something spilled on the table (who
knows when) that was fine with the old solvent based finish, but
without 100% removal, will not allow your new water based poly to dry.
If the alcohol bath didn't outright dissolve the original finish, then
it was probably one of the 1,000 different blends of lacquer. What
you did with the alcohol was simply clean the grime off the surface.
My solution to this would be what my solution always is on these
problems... start over. Go buy a good stripper, strip off ALL the
finish to make sure you leave no contaminates behind. Sand lightly as
needed to take off the remaining resins that redissisolved with the
stripper. Clean off the surface with lacquer thinner and really clean
rags. Apply final finish.
If the wood is really clean, you shouldn't need a barrier coat of
anything like shellac. If you have your doubts, a quick spit coat of
sanding sealer only takes a few minutes
to apply, and it is compatible with anything you want to put on top of
For me personally, my experience has been that when finishing/
refinishing wood that has a chance of contamination, I get better
results with a solvent based top coat.
I'm just seeing this thread for the first time and didn't bother to look up
the original post, so I may be a bit off base. So, what's new huh?
I'm not sure this sounds like contamination to me Robert. I'm not seeing
him complain about adhesion problems or any other indicators of
contamination or incompatibilites between finishes. This sounds like a
problem with the finish at hand. I'd like to know how heavy the finish was
sprayed on. Humidity level is high so I'd expect a water based poly to be
pretty slow under those conditions. Temp is fine, but it's more about
humidity with water based stuff.
I'd like to hear a little more detail from the OP on how he sprayed this.
What type of gun, how many coats, how long between coats, how heavy were the
coats? Was the OP seeing tack between coats or was this drying problem
evident throughout the spraying process? Any other incidentals like
tendency to run (indicating a way thin product), etc.
I too resort to this approach, but in this case I think I'd wait 24-48 hours
and see what the situation is. I'd probably throw a light at it too, in
attempt to encourage drying.
Tue, Dec 11, 2007, 5:31pm (EST-1) email@example.com
(sweet sawdust) 'did' ssayeth:
<snip> cleaned with denatured alcohol. <snip>
Dunno if it figured in, but thou did 'not' sayeth how long thou let
I do things I don't know how to do, so that I might learn how to do
Sounds to me like an oil/water reaction. Whether it was old finish
partially dissolved but not completely removed, or something in the
finish remover you were using, I don't know. But there was something on
the surface keeping that water based poly from drying like it should.
You can try starting over again, but you might have a problem getting
all the old finish off without sanding right through the veneer.
He's not reporting any adhesion problems which would be expected with an
oil/water reaction. No blisters, no lifting, no fisheye, nothing that
sounds like a contamination of any sort. I'm curious what you may have
experienced with water based poly that causes you to suggest this. One
never stops learning ya know.
I've never had that reaction with water based poly, but then I never put
it on over an old oil based finish I had tried to remove. Based on the
fact that he said he used the same batch of poly on another project
without problems, I ruled out problems with the finish itself or his
application. Simple deductive reasoning tells me it must be a problem
with something on the surface. I confess that oil/water reaction was a
guess. <g> The only other thing I could think of is that maybe he put
the poly on before the alcohol had dried.
Ah. Thanks. From his reply I'm thinking it is more a combination of his
application of light coats (before each coat cures) and the sorta high
humidity. It's not killer humidity and I've certainly sprayed a lot of
stuff at that level, but he did say rain was moving in and that'll hurt the
I agree with you about thicker coats.
For those of you like me, without spray equipment, I've had very good
success with the following technique if I want a really glass-smooth
surface: Apply several thick coats, allowing to dry completely and with
a light scuffing in between. Then sand this buildup down through 400 or
so, and apply the last coat carefully with a foam brush.
"In answer to the questions in the replays to my query:
The Alcohol did soften and remove most of the old finish but not all,
the finish acted like Shellac. The adhension of the new finish was good
except in one or two spots on the part that was washed only, I have since
sealed those spots. There was no tack between the first and second coats,
finish was soft but not tacky to the touch, you could dent it (barely) with
a fingernail but it would not stick to your hand or leave an imprint. Run
was slight to none the product had not been cut and was straight out of the
can. I used a HVLP spray gun on a light setting, I prefer several coats to
one or two heavy coats. From the final sanding after the last wash to
spraying was in excess of 24 hours, time between first spray and seconed
spray was about 4 hours. The veneer is getting thin and I would hate to
resand the top, probably be eaiser to make a new top.
After 14 hours of drying I checked the finish, it had gone from milky white
to crystal clear, still not a hard finish, can be dented with a fingernail
but not tacky. I sanded the finish and it sanded with out pills or loading
the sandpaper (220 grit). Surface of table was wavey not smooth, it looked
like the finish did not flow properly, the sanding gave it a smooth surface.
I resprayed and within 5 minutes the new finish was again the color of milk.
I am going to put a spot light on it to try to heat is slightly and see if
that helps. I am wondering if it is a combination of high humidity and
I don't spray water based poly so you'll have to correct me if the
manufacturer suggests something different, but I don't initially like the
idea of the first coat being soft when you shoot the second coat. If I'm
correct, this finish cures by evaporation - right? In that case you'd want
to put on a heavier coat and let it dry thoroughly. Scruff it and put on a
second coat. Poly does not burn in to the coats below it so when you apply
coats - even light coats over coats that are not fully cured, you are
trapping the carrier in there. It will make its way up and out but that is
going to delay the curing time of the subsequent coats.
As a rule, spraying light coats is not a preferred technique. Of course, we
all have our definitions of what is light and what is heavy, but a heavy
coat covers more evenly, and with less surface distortion caused by the
Hey Mike, how ya doin'? Don't see you around much anymore.
idea of the first coat being soft when you shoot the second >coat. If I'm
correct, this finish cures by evaporation - right?
In my personal experience, a tack or soft coat can be good for solvent
based finishes, but don't know anyone using that technique for water
based. (PING - Barry...) And of course, NONE of the manufacturers
endorse a tack coat for any of their final finishes.
I have read how some of the newer, more sophisticated water borne
finishes cure, and I'll tell you, you have to be a Chinese
mathmetician to understand the science of the the cobination of curing
polymers. I think in this case it actually depends on the type of
finish you use whether it is MLC, Target, Fuhr, etc.
trapping the carrier in there. It will make its way up and out >but that is
going to delay the curing time of the subsequent coats.
Nicely said. There is no reason to put on thin coats of poly unless
you can't control the finish texture. Put it on the manufacturer's
receommendation and follow up coats as directed. It sounds like you
were >right on the money< with this as he does say that it did cure
out later... so it seems this would be at least a large part of the
And check this out. One of the boys on WoodWeb described the hole he
fell into by using some of the new water based finishes with multiple
thin coats. After he put on one coat, he waited until it was tack
dry, then applied another, then another. In effect, what he did was
build a sandwich of layers that made it impossible (after the very top
of each coat dried) for the product to off gas and cure. Since the
first of four coats was down so deep, the solvents in the finish (see
below) may have discolored the wood! His project was sticky for some
time (couple of days?) as he screwed up the manufacturer's
instructions. Luckily, it cured out while he was frantically trying
to find out ways to keep from having to strip and start over.
A common mistake is to think that these water based products are
"safe". NOT SO. They are filled with different poisons, not much
better than the old solvent based stuff. Formaldhyde, ammonia(s),
alcohols, stereates, and all kinds of other nasty stuff are in these
mixtures. That's one reason I am not on water based stuff now.
Besides, I agree with Mike. The solvent based stuff does smell
better! I got a laugh out of that one! I am just thinking of a day
of spraying with a leaky mask.... YIPEEE!
I STILL think there was something left on the table top, even if it
was just some left over moisture held in the old finish. Cool
weather, mild temps, and the use of alcohol may have been a
contributor. After all, even though the alcohol was at 80%, that
means it was still 20% water he was washing with.
I didn't originally go to the contaminated finish/gun road as my
personal experience with contaminated finishes is that they are
erratic, and don't follow a pattern. A -uniform-, cloudy finish
seemed to point somewhere else.
Full, wet coats for MLC Ultrastar. No tacking, and don't build too many
coats. Once I'm happy with color, I'll usually go one coat of Zinnser
Seal Coat and two coats of Ultrastar. If I want a deeper build, I'll
use a second coat of shellac or add a coat of Ultrastar Sanding Sealer.
For solvent stuff, I flow-coat the last coat, but don't tack it. I've
really come to like the Kwick-Kleen "Fast Dry Poly" when I need more
durability than NC lacquer.
The big attraction for WB is no fire hazard, easy cleanup, and excellent
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