I've never tried a water-based poly until today, and I have run into a
problem. Admittedly, I am experimenting a bit. The problem is a crackled
finish. Here are the details of what I did.
I volumteered to refinish my parent's kitchen table as payback for my Dad
helping me deliver finished projects to customers. I started out by
sanding the entire table top down to bare wood. I finish sanded it up to
220. I applied a coat of shellac as a seal coat. That dried over night.
Next day I applied a water-based glaze tinted with Transtint dyes. That
dried over night. I was only doing the top, so I was trying to get to the
color of the rest of the table and chairs. I felt that I needed to warm up
the tone a bit, so I tinted the water-based poly with Transtint dyes, and
sprayed a coat. It sprayed great despite being a brushing product. As it
dried I began to notice some issues. Slowly it began to crackle. It looks
kind of cool, but this is not what I was going for. Any clue why this
Other contributing factors may have been: Temperature in the shop (it was
very cool in the early day, but I had the heat on for hours before I
started). Heating with kerosene. Could that have contaminated the
surface? Anyone experienced this?
It reticulated. Possible causes...
1. Final coat wasn't compatible with previous.
2. Previous coat wasn't totally dry. When the last coat was sprayed and
dried it shrunk and cracked as the coat beneath it continued to dry.
3. Same as #2 but both coats were the final one; i.e., sprayed,
partially dried, sprayed again with same material.
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Brian, I doubt that it's the reason for your problem but you do know NOT
to use waxy shellac as an undercoat, right? Always used de-waxed
shellac under other finishes. I use a compatible sealer when I spray
waterborne polys and I've never had any issues with cracking, bubbling,
peeling, blushing, or any other surface defect so I'm not too good at
diagnosing problems as I've not had to solve any. (Now with regards to
regular poly...that's another story)
The shellac was dewaxed, but it did occur to me that I ran a tack cloth
over the whole thing just before I sprayed. It was one of those ones you
get at the hardware store. I forgot about that. Could that have left
stearates on the surface? Would that have caused the problem. I may never
know, but I'll change a variable next time and see what happens. I'm going
to sand the finish off soon and try again.
It could leave OIL on the surface. That shouldn't cause the cracking, as
far as I know. Jeff Jewitt and Bob Flexner both have excellent books on
I use sterated papers between coats of WB poly and never have a
problem. Now the same paper, when used with Minwhacks poly causes me no
end of problem with cratering. I'm not a fan of using tack cloths and
have abandoned their use altogether. I use a combination of a type of
cloth who's type and composition I can't describe, other to say it's
sort of "waffle" looking, and compressed air. I like blowing out pores
before and between sanded coats of finish. You can wipe a surface all
day long and not remove debris from the pores.
I'd suspect the kerosene.
I once finished a piece in water-based poly, and another in oil based
poly. I set them to dry within a few feet of each other, and the
water based piece finish got really messed up. I'm pretty sure it
reacted to the volatile solvents in the air from the oil-based poly.
On other occasions with the conditions in the room the same, the
water-based poly OR the oil-based poly finish turned out fine when
they were drying alone.
Kerosene heaters leave a fine oil film, so this may have reacted with
the water-based poly like the oil-based poly solvents did.
I'm now careful to keep water and oil based poly apart, but wonder if
I just happened to use a formulation of water-based poly that has that
reaction. The stuff I used was Minwax Polycrylic on maple.
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