Problem with Finish

[Fudgester]

I'm currently finishing my first bass project (just the back at the moment) and I cant figure out why an area of the wood just won't take the polish.

The strangest part is that I had this problem earlier, but I overcame it (not exactly sure how).

This is the stuff I am using:

The solvent:
http://www.imagehosting.com/

Unfinished side (front):
http://www.imagehosting.com/

Finished side (back):
http://www.imagehosting.com/

And the problem:
http://www.imagehosting.com/

Any help would be appreciated.

Thanks in advance!

 

[vbasscustom]

non of the pictures showed up actually. i probably couldnt help you anyway, the most intricate finish ive done is a hand rubbed tru oil

 

[Fudgester]

Damn thing, proberbly because they're too high res.
Well basically the 'french polish' has refused to go on just a small area of the bass, it has happened before but I (somehow)managed to repair it.
I'm lonely and confused.
Please help me!

 

[leswatts]

Your'e french polishing a bass body? With dewaxed shellac?
Wow.

Perhaps some oil of some kind got on the wood in a spot before you started?

Or is the wood just drinking up the finish in a spot?

A retry in posting the pictures at lower res will help...

Les
L M Watts Technology

 

[Fudgester]

I will do that!
and it's ready mixed stuff with shellac, so it's not terrorbly diffucult.

 

[Fudgester]

[Invalid or Expired Link Removed]

 

[vbasscustom]

is that life magazine i see? :/

 

[leswatts]

Ah...ok. You mean that bubbly spot on the bottom of the picture in the roundover area?

I teach french polishing from time to time. It looks like some kind of open pore exudation or something.

Let me ask a couple more questions:

Are you using Behlen Qualasole? If not what brand?

Are you doing the traditional french polish with the hundreds of coats put on with a dry rubber that makes circular halos
where you rubbed that last about a second?

I see some cotton balls in the upper left. Did you put fairly wet coats on with those?

In any event if it's just a rough spot you can sand it. Some rubbed on coatings soak in open pores then exude back out later, making a crater. Normally a traditional french polish doesn't do this though.

Tell me more about the bad spot.

Les
L M Watts Technology

 

[SDB Guitars]

I'm guessing when he's talking about the problem spot, he means the dry-looking patch in the right-center area of the back...

 

[62bass]

If it's not sticking in that large area then I'd suspect something in the wood like oil or silicone or glue is causing it. Usually I'd suggest sealing that with a de-waxed shellac and then finishing over that, which usually solves the problem. My experience is with varnishes though. Since you're already using a shellac product I would expect it to stick quite well, but possibly the oil in the french polishing blend you're using is preventing it. However, you might give that a try. Give the bass a very light sanding with 600 grit paper and wipe all the dust off. Seal the entire body with a coat of de-waxed shellac. You can get this in a quart can. It's called Zinnser's Bulls Eye Seal Coat. Otherwise you have to make it up yourself from dry shellac and solvent. Use the Seal Coat. It makes life a lot simpler. It's a 2 lb cut clear shellac in a can. Most high end paint stores should be able to get it for you. Give it a very light sanding when dry and then try another coat of french polish.

I just paused here to consult my "bible" on finishing-Jeff Jewit's "Hand Applied Finishes" and he cites two examples of french polish not sticking. One is caused by too much oil in the polish and can be corrected by wiping the oil off with naptha (lighter fluid is a good source for small amounts of naptha), then continue applying finish. The other is caused by working one area too much and each subsequent coat pulls off the previous coat. You might want to check your application technique. Also, make sure you're giving the lacquer enough time to dry between coats.

Note that he is talking about traditional French Polish and not padding lacquer which is a bit different. And I'm not an expert in using padding lacquer.

If none of this helps, wait for an expert in using padding lacquer to show up here. Maybe leswatts will know.

 

[praisegig]

Jeff Jewit's "Hand Applied Finishes" and he cites two examples of french polish not sticking. One is caused by too much oil in the polish and can be corrected by wiping the oil off with naptha (lighter fluid is a good source for small amounts of naptha), then continue applying finish. The other is caused by working one area too much and each subsequent coat pulls off the previous coat. You might want to check your application technique. Also, make sure you're giving the lacquer enough time to dry between coats.

Note that he is talking about traditional French Polish and not padding lacquer which is a bit different. And I'm not an expert in using padding lacquer.

If none of this helps, wait for an expert in using padding lacquer to show up here. Maybe leswatts will know.

Both examples could be happening. If you are using ready mixed padding lacquer, no addition oil is needed on the pad. You also need to continually keep the pad moving, but not over the same spot. Move in a figure 8 pattern, and when starting/stopping, be sure to go off over an edge (much like an airplane landing on an aircraft carrier). Using a sealer coat of shellac can provide a quick film build, to allow bite for the padding lacquer. Shellac will also seal in any contaminate that may be present, I would do 2 or 4 washings of naptha (using a clean cloth wit each washing) to clean the area, before sealing with shellac.