Shellac not sticking to one spot

[Satnam Singh]

I'm trying to finish an ash telecaster body. I decided to go simple, no pore fill, maybe 3 coats of Waterlox, but first I wanted to experiment with getting a butterscotch blonde color by mixing up some Mixol (yellow, white and dark red, with a touch of amber/brown). I don't like the way oil stains look, so I decided I would try putting the Mixol in a light cut of shellac before the Waterlox (I did put down on coat of Waterlox as a sealer before going with the color).

I tried using Preval sprayer, but I got so much sputtering that I gave up. I decide to wipe on the color/shellac, knowing full well the pitfalls of wiping color in shellac.

I'm not expecting a professional finish (no pore fill, wipe on translucent finish), but I'm still trying to get the best I can.

I'm satisfied with the result save for one area, maybe 3" by 5" on the back, that just doesn't seem to take shellac/color. Contamination? I thought shellac is the premier barrier coat. Over sanding in that one spot? I tried roughing up with 220 grit.

BTW, the mottled look on the area in question is do to a latest attempt to dab on shellac/color, that failed.

Any ideas?

[David King]

It seems like your first coat of waterlox maybe didn't dry in that spot. Can you smell the waterlox in that area? Apart from that it's going to be a lovely guitar.

[Satnam Singh]

Thanks, David.

I wouldn't think it was a drying issue. It's been about a month since the Waterlox was applied. In the meantime, I had been Waterloxing a couple of necks, applied Tru-oil style (multiple, thin coats), in the garage. The body seemed sufficiently dry and odor free that I had been able to bring it into the house.

[Dennis Weaver]

Don't mistake me for someone who knows what's what, but just a thought I had-

Maybe it is nothing to do with what you did. Maybe it is glue from the Fender factory which they used to glue the body boards up with and it sufficed to have a remnant of it in the wood for their finishing but not your clear finishing.

In which case you might have to sand the whole back down like 1/32" and refinish. Might have to do that anyhow regardless.

See what some people who are more qualified say perhaps. I would think- strip and redo and if doesn't match then sand.

Or... darker finish?

[Satnam Singh]

Thanks for the ideas, Dennis. I'm no expert either, but my thought here is that the color coat is a surface thing, rather than a dye which would soak into the wood fibers. I realize some shellac/alcohol would migrate into the wood, but between the color coat being on the surface, and the sealer coat of Waterlox, I thought I would have sealed out a glue or other contaminant issue.

I think it was on this forum, years ago, I saw Rick Turner comment that he used Waterlox as a tie coat between coats of different finishes. It may be that I didn't use enough sealer/Waterlox. It was just one heavy coat, which soaked completely into the wood.

[Barry Daniels]

It almost looks like what happens to lacquer on silicone contaminated wood which results in fisheye. In that situation, the finish is repelled from the wood and you can't get surface build in that area. Could you have gotten any wax on the wood that wasn't removed in the sanding and prep stages?

[Satnam Singh]

Hmmm. You've given me some ideas. While I don't think I introduced something in the prep stage, a couple of possibilities:

After the preval sputtered on me, I did some sanding to even out the splatter before continuing with the wiping. I used a rather fine grit, 400 or 600. Could I have burnished the wood in that spot to have caused such problem?

Or, could the wrong type of sandpaper introduced something into the would to cause a problem? Does silicon carbide paper cause such issues?

If one of these issues is causing my problem, what is the solution? I'm guessing shellac doesn't seal out a silicon issue. Would sanding with 220 resolve either issue?

Am I off base?

[Peter Wilcox]

It seems like there is a contaminent in the wood, whether it is internal (it came that way) or external (something you did.) Frankly, you're spending time trying to correct the defect that might be better spent removing what's there and starting fresh. If it were me, I'd sand the back to wood and start over with the finish - but that's easy for me to say, since I have a drum sander. Alternatively, you could wipe the back with alcohol and get off what you can and see what it looks like. For whatever reason, I don't think you're going to get that spot to match the rest by simply treating that area.

[Satnam Singh]

Yeah, I've been coming to the same conclusion. Probably a contaminant, may never figure just what is was, but I have to get rid of it.

I've been searching the web, and seen Jeff Jewitt quoted as suggesting wiping it down with a 50/50 alcohol/water mix. Other suggest a solvent compatible with the finish (I guess that would be alcohol again). As to the sanding option, I'm working by hand; any suggestion as to what grit?

I'm guessing after a finish the contaminant removal phase, I can watch the first coats of alcohol/color to confirm the contamination was successfully removed.

It's still curious to me that shellac is sometimes recommended to seal contaminant for other finishes. Guess I'm just learning the art the hard way.

Thanks again.

[Peter Wilcox]

As to the sanding option, I'm working by hand; any suggestion as to what grit?

I would do 120, then 220 and 400. Before I got the drum sander, I used to use a belt sander for the first stage of a job like this because I'm lazy.

[Michael Lewis]

It is unclear from your photo due to the "hot spot" of reflected light, but you mentioned sanding with very fine grit. That can 'polish' the harder areas of the wood, like the hard late wood, and that can cause stain resistance because the color can't get in. Generally 220 grit is used to even this issue. You need a scratch pattern (like 220 grit paper) in the wood surface to give the harder and more resistant areas some 'tooth' for holding the color.

If your shellac is crawling away from the area it could be one of two causes: grease or oil contamination, or too much alcohol. Alcohol tends to crawl away from a pool, and leaves a border around the wet area. You can see this happen if you apply alcohol solvent finish too heavily.

[Mark Swanson]

I would have put the shellac on before anything else, starting with a wash coat of clear shellac first. I think you are having problems since you first put down a waterlox coat, and then shellac, and the waterlox sealed that area better than other areas. I think I'd sand it back and re-apply the entire back.

[Satnam Singh]

Regarding Waterlox as sealer, certainly a possibility. This project was sort of a test case in that regard.

The body is a USA Custom Guitars "web special." It appears that there is some worm hole filling on the back. It may be the filler used affected the Waterlox/shellac from adhearing, but it doesn't seem that most of the filling is in the same area.

I may never figure out what the cause is, but I did take the finish off the back with alcohol (20 minutes work), then followed up by sanding with 220 grit. I hope to start reapplying shellac/mixol color today to see if I get better results.

[Jim Hepler]

Satnam,
I've had that problem a couple of times. It's hard to be sure, but I've come to believe that my sandpaper from the local hardware store had some contaminant in it, possibly to help it keep from clogging. My experience was that when I had a spot that wouldn't take shellac, I would sand it back fairly aggressively, and the problem was at least as bad. I switched to scraping the area with thin scrapers that Lee Valley sells. I like to grind the corners a little round to prevent accidental digging in. They say they are good for scraping finishes. Once I had thoroughly scraped the area, I was able to apply shellac no problem. Incidentally, I also found that when I got some ridges in my finish (I'm just learning about applying shellac), I could use the scrapers to flatten the high spots just by going pretty gently. My experience with scrapers has yielded my best finishes so far, so I think I'll continue to explore that way of doing things. I'm not an expert, but that's my 2 cents.
jim

[Satnam Singh]

A belated update:

"If your shellac is crawling away from the area it could be one of two causes: grease or oil contamination, or too much alcohol. Alcohol tends to crawl away from a pool, and leaves a border around the wet area. You can see this happen if you apply alcohol solvent finish too heavily."

We have a winner. I had mixed a very light cut of shellac, thinking just enough shellac to serve as a binder for the Mixol color. Having removed the color on the back and started over. Worked ok until I got a little heavy in one spot. Same issue different spot.

Started over again, this time rather slow, french polish style. Much better.

Thanks