Finish Crazing

[John TenEyck]

I just finished a piece, as follows:

Sprayed 2 coats of shellac/dye toner, let cure over night
OB Gel Stain glaze, wiped on/off, let dry 24 hours
Sprayed SealCoat shellac sealer, let cure 3 hours
Sprayed 2 coats of GF Clear Poly

Everything was fine until I sprayed the first coat of GF Clear Poly. After it dried for about 3 hours I sanded it lightly with a 320 mesh sanding sponge. At that point I noticed spider lines in a few areas. Most areas were perfect, but where the spider lines were they were easy to see because the white sanding dust accented them. After I vacuumed and wiped everything with a microfiber cloth I sprayed the second coat of finish. That coat came out fine, but you can still see the spider lines underneath if you look very closely.

So, any idea why this happened?

John

[Steve Jenkins]

It's possible it could be the fault of the gel stain. I had a similar problem using a glaze under conversion varnish I found that I needed to use a vinyl sealser between the glaze and the topcoat. My thought is that if the gelstain wasn't wiped off completely it could act kind of like a glaze not truly hardening.

[Jim Rimmer]

John, you are one of the guys I would ask if this happened to me. :eek: :D I hope you figure it out and let us know.

[Prashun Patel]

Is your Sealcoat bad? If yes, then is it possible that 3 hours wasn't enough to dry such that when you put the fast drying GF poly on top, the shellac continued to dry and shrink causing the GF Poly to craze?

I got similar results with Sealcoat under Target USL a couple years ago. I read on Target's website of suspected incompatibilities between dewaxed shellac and Target USL, but I think my problem was just moving too quickly between the coats.

I agree with Jim. This is rocking my world a little...

[Rich Engelhardt]

The "what" is easy - there's a loss of adhesion between two coats.

The "which two coats" is the hard part. Any way you can use a magnifying glass or something to try and see which coats separated?
It should be pretty easy to see if it's the gel stain separating from what's under it.
The others - not so much.

[John TenEyck]

Thanks for the replies, all. I confirmed the SealCoat is good. The gel stain was wiped super well since I was trying to put it in the pores of the wood only. I haven't tried looking at it with a magnifying glass, but that's a good idea Rich and I will do so. More to follow.

John

[John TenEyck]

OK, I looked at the finish under a magnifying glass, but it was inconclusive. Here's a photo that you might be able to see the little spider lines I'm talking about:

300093

I think I might have an explanation for what happened. The temp. in my shop was 64 F when I sprayed that first coat. The minimum application temp. is 60 F. The temp. outside was in the 50's and outside air was back-flowing through the exhaust duct onto the piece after I sprayed it, because I forgot to close off the damper when I shut down the fan. I think maybe the temp. got too cold and that's what caused the finish to craze. Make sense?

John

[Rich Engelhardt]

Could very well be.
A lot of the newer finishes can be real touchy about temperatures.

(by "newer" I mean anything made in the last 20 years or so)

[Phil Thien]

John, you are one of the guys I would ask if this happened to me. :eek: :D I hope you figure it out and let us know.

Exactly what I was thinking.

[Rich Engelhardt]

OT - but - congrats old buddy!
Just in time for the SMC Holiday gala eh?
I hear they pick you up in a limo, take you to the airport where the SMC private jet whisks all the staff off for a weekend in the Bahamas - where they pass out the $100,000.00 bonus checks for being on staff! ;)..

(Either that, or you zigged when you should have zagged and got caught mot being able to say no and run!)

"Prashun Patel (http://www.sawmillcreek.org/member.php?17220-Prashun-Patel)
http://www.sawmillcreek.org/images/statusicon/user-offline.pngModerator"

[Conrad Fiore]

Is your Sealcoat bad? If yes, then is it possible that 3 hours wasn't enough to dry such that when you put the fast drying GF poly on top, the shellac continued to dry and shrink causing the GF Poly to craze?

I got similar results with Sealcoat under Target USL a couple years ago. I read on Target's website of suspected incompatibilities between dewaxed shellac and Target USL, but I think my problem was just moving too quickly between the coats.



I agree with Jim. This is rocking my world a little...

It wasn't a problem with dewaxed mixed from flake, it was a problem with SealCoat and the Target products. There are instances with incompatibility due to a pH issue between SealCoat and Target products, especially when the SealCoat was applied in a heavy film.
If you continue to have issues, I would first test the GF over just the SealCoat and if that is the problem, put a barrier coat of dewaxed shellac from flake over the SealCoat.

[Prashun Patel]

That's interesting. What is different between Sealcoat and shellac from flake? Does Sealcoat contain additional ingredients in its solvent besides denatured ethanol?

[Conrad Fiore]

That's interesting. What is different between Sealcoat and shellac from flake? Does Sealcoat contain additional ingredients in its solvent besides denatured ethanol?

I believe it does to increase shelf life.

[John TenEyck]

How can SealCoat have a pH? There's no water in it. No water = no pH. There may be a compatibility problem between SealCoat and Target's product(s), but it can't be due to pH.

John

[Conrad Fiore]

I'm repeating what the owner and developer of Target products has stated. I'm not a chemist, just repeating what has been hashed out at the old Target forum many times.

[Rich Engelhardt]

How can SealCoat have a pH? There's no water in it. No water = no pH. There may be a compatibility problem between SealCoat and Target's product(s), but it can't be due to pH.

Technically - you're correct.
Shellac has no pH - but - shellac is an acid.
You run into a compatibility issue with the acid shellac going over the basic Target.

[Ethan Melad]

For what its worth, I was recently told by Target that their products will be compatible with 1# shellac - Zinsser Sealcoat is a 2#, so it just needs to be cut. Maybe GF has the same issue?