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Water base finish effecting top and back seams
http://www-.luthiersforum.com/forum/viewtopic.php?f=10101&t=41048		 Page 1 of 1
Author:  Bryan Bear [ Mon Aug 05, 2013 10:32 am ]
Post subject:  Water base finish effecting top and back seams
I am trying a water base finish (poly whey) for the first time and having some trouble. Anticipating problems with water, I sealed with a few spit coats of shellac so I am confused as to what is going on. The finish is building fine and I’m happy with it so, though I'm still getting used to it. The problem is that all the plate seams, which were joined with HHG, are showing a distinct line in the finish. The joints are good, without the color/grain change, I couldn’t locate them by eye until I started finishing. Obviously, water is getting into the wood and swelling it. I assume the joints themselves are not compromised, but I am not sure if I should keep building and then level sand, or if that will cause more problems. How long do I need to wait before I level so that I know moisture is equilibrated? After I level sand, I will need to do at least one more coat (won’t I?) will this just reintroduce the problem (or is the problem caused by the first application and sealed thereafter)? I know a lot of you have used various water based finishes before (not necessarily poly whey), how common is this problem and what are the solutions?
Author:  brazil66 [ Mon Aug 05, 2013 11:19 am ]
Post subject:  Re: Water base finish effecting top and back seams
Is it dewaxed shellac? Are you thinning the PolyWhey (don't)? What version of the PolyWhey is it.?
Author:  B. Howard [ Mon Aug 05, 2013 11:29 am ]
Post subject:  Re: Water base finish effecting top and back seams
Shellac does not seal against water very well, even of it is dewaxed.
Author:  Bryan Bear [ Mon Aug 05, 2013 12:40 pm ]
Post subject:  Re: Water base finish effecting top and back seams
Yes, dewaxed, pumice pore fill. Luthier's blend gloss poly whey un-thinned. I'm applying with a foam brush.
Author:  SteveSmith [ Mon Aug 05, 2013 12:46 pm ]
Post subject:  Re: Water base finish effecting top and back seams
Same issue here with PolyWhey. On a headplate that was joined with fish glue or HHG, I don't remember which. I've been able to cover up about half the line by sanding back, another seal coat of shellac (yes it's dewaxed) and more PolyWhey (luthier's blend and,no, it's not thinned). Very annoying, to say the least and could end up being a showstopper for this finish. I never encountered this problem with EM6000, or for that matter, the one other time I used Polywhey.

Top is joined with HHG and have seen no issues there.
Author:  Michael.N. [ Mon Aug 05, 2013 12:48 pm ]
Post subject:  Re: Water base finish effecting top and back seams
Shellac should be sufficient to seal against a water based finish surely. Perhaps you need more seal coats of Shellac.
I sometimes see a similar problem with wet sanding and cutting through the finish. More shellac cures the problem, it builds and seals the glue lines but then again I'm not using a water based finish.
Author:  Bryan Bear [ Mon Aug 05, 2013 1:38 pm ]
Post subject:  Re: Water base finish effecting top and back seams
Steve, did you sand back to bare wood or just to level the finish?
Author:  Mike Collins [ Mon Aug 05, 2013 2:03 pm ]
Post subject:  Re: Water base finish effecting top and back seams
I use a thick shellac coat.
Two coats.
Maybe a 3lbcut.

Then let dry & sand back to the wood.
Then apply another thin coat.
Let dry & finish with the waterbase.

Was your HHG fresh?
To thin a shellac mix may have allowed the
Alcohol to attack the HHG.

Mike
Author:  Tony_in_NYC [ Mon Aug 05, 2013 2:16 pm ]
Post subject:  Re: Water base finish effecting top and back seams
Allow me to interject my two cents having never used this product or experienced this problem.
It sounds like the glue line is sunken versus the surrounding wood, is that correct?
It sounds like the wood that has glue in it is not expanding, while the rest of the wood is expanding from the moisture/ water content in the finish.

If shellac is not sufficient to prevent this, would not a spit coat of lacquer be enough? I have brushed on very thinned coats of lacquer as a sealer when I knew the box would sit around a while before final finishing, just to prevent it from getting dirty. Worked great. Might do the trick here too.
Author:  SteveSmith [ Mon Aug 05, 2013 2:35 pm ]
Post subject:  Re: Water base finish effecting top and back seams
Bryan Bear wrote:
Steve, did you sand back to bare wood or just to level the finish?


Bryan,

This was after I level sanded with P600, carefully. Before that was:
1. ZPoxy, sanded to bare wood
2. 2 coats of about 2# ish cut of shellac
3. 4 coats of polywhey
4. Sand back with P400
5. 4 coats of polywhey.

The guitar sat in the drying rack for about 16 days before I started sanding on it.

No way this should have done what it did, it's in the center of the headstock in an area that is highly unlikely to get sand-throughs. Very strange. I thought I had some kind of weird contamination or something. Kind of happy and sorry at the same time to see someone else having the same problem. I've seen no other problems on the guitar but binding and rosette were installed with CA.

I'm about ready to go buy a gallon of nitro. [headinwall]

I may try putting some more shellac on it, then put some CA over it, then more shellac and more polywhey. Not sure at the moment.
Author:  Bryan Bear [ Mon Aug 05, 2013 4:06 pm ]
Post subject:  Re: Water base finish effecting top and back seams
The HHG was fresh. I don't think the alcohol was the issue because I have never had this problem before when using shellac and I have used more alcohol for pore filling in the past than I did here. Further, the problem didn't show until I started to use the poly whey.

Tony, I'm not 100% sure what is going on. The line is so thin I can't really say. Either the poly whey is not sticking to/repelled by the glue line, or the glue line shrunk, or didn't swell.
Author:  Bob Menzel [ Mon Aug 05, 2013 4:35 pm ]
Post subject:  Re: Water base finish effecting top and back seams
Quote:
To thin a shellac mix may have allowed the
Alcohol to attack the HHG.


Never heard about this before. Alcohol attacks HHG??
Author:  SteveSmith [ Mon Aug 05, 2013 4:49 pm ]
Post subject:  Re: Water base finish effecting top and back seams
My shellac is fresh and about a 2# cut made with dewaxed flakes and Everclear. Can't see that being a problem.

Also, the only new material in my finishing this time was the Luthier's blend Polywhey.
Author:  mhammond [ Mon Aug 05, 2013 11:27 pm ]
Post subject:  Re: Water base finish effecting top and back seams
I have noticed the same thing with water based. I think the HHG is swelling with the moisture, it seems to shrink back with time. When it sits a week or three for hardening/buffing purposes it will go back to flat or very close. It really freaked me out the first time, but 40 some instruments later, I don't worry too much about the little lines.

Mikey
Author:  Mike Collins [ Tue Aug 06, 2013 11:05 am ]
Post subject:  Re: Water base finish effecting top and back seams
Everclear is 5%water.
Mike
Author:  SteveSmith [ Tue Aug 06, 2013 11:55 am ]
Post subject:  Re: Water base finish effecting top and back seams
Mike Collins wrote:
Everclear is 5%water.
Mike


I understand that, just was pointing out I didn't mix with DNA from the big box store which I expect has a lot more water in it.

Are you thnking that 2# cut shellac made with Everclear is "too thin"?
Author:  Mike Collins [ Tue Aug 06, 2013 1:10 pm ]
Post subject:  Re: Water base finish effecting top and back seams
The alcohol evaporates fast & leaves the water.
Do a search for water free alcohol & use that.
A thicker mix is better as a sealer.
Just allow drying time.

A first lite coat will raise the grain.
Then let dry.
Sand with nothing finer then 320.
If ya go through wipe on some Shellac with a lint free cloth.
Then add the thicker coats.
Let dry!
Scratch them up with Synthetic steelwool.
Then add your top coats.
Mike
Author:  SteveSmith [ Tue Aug 06, 2013 3:02 pm ]
Post subject:  Re: Water base finish effecting top and back seams
Mike Collins wrote:
The alcohol evaporates fast & leaves the water.
Do a search for water free alcohol & use that.
A thicker mix is better as a sealer.
Just allow drying time.

A first lite coat will raise the grain.
Then let dry.
Sand with nothing finer then 320.
If ya go through wipe on some Shellac with a lint free cloth.
Then add the thicker coats.
Let dry!
Scratch them up with Synthetic steelwool.
Then add your top coats.
Mike


Thanks Mike!

Edit: found some and got it on order.
Author:  Bryan Bear [ Tue Aug 06, 2013 3:41 pm ]
Post subject:  Re: Water base finish effecting top and back seams
Won't 100% alcohol become about 96% alcohol shortly after opening the bottle and exposing it to RH??
Author:  WaddyThomson [ Tue Aug 06, 2013 3:44 pm ]
Post subject:  Re: Water base finish effecting top and back seams
It's the "denaturant" (may not be a word!) that keeps it stable.
Author:  Colin North [ Wed Aug 07, 2013 12:28 pm ]
Post subject:  Re: Water base finish effecting top and back seams
Mike Collins wrote:
The alcohol evaporates fast & leaves the water.

Mike

Actually, that may not be true.
"Water and ethanol form an azeotrope - a mixture whose composition can't be changed by distillation - at a ratio of 95.6 : 4.4 ethanol : water.
In this mixture, the vapour has the same constituent ratio as the solution."
Author:  Mike Collins [ Wed Aug 07, 2013 12:57 pm ]
Post subject:  Re: Water base finish effecting top and back seams
I understand.
But denatured can have any amount of water or who knows
what in it.
No two are the same mix!
Mike
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