Water based poly problem


Hello,
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 happened?
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?
Thanks, Brian
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Brian Mahaney wrote:

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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What brand poly were you using?

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On Tue, 21 Feb 2006 00:50:32 GMT, Rumpty wrote:

Ace Brand. From the hardware store, for experimentation.
Brian
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Brian Mahaney wrote:

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)
Dave
Dave
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On Tue, 21 Feb 2006 09:00:56 -0800, David wrote:

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.
Brian
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Brian Mahaney wrote:

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 finishing.
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.
Dave
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Many of the modern polys are not compatable with shellac. Some manufacturers will even recommend you use only their matching sealer.

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Suggest you ask that question at the site below. You need to register but it does not generate any spam. JG
http://www.homesteadfinishing.com/phpBB2/portal.php
Brian Mahaney wrote:

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On Mon, 20 Feb 2006 22:22:24 GMT, Brian Mahaney

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.
YMMV.
...John
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