Moisture-damaged finish

Ouch, was it in it's case when it got rained on?

 

What's the finish?

You can test to see if it's finished with shellac (aka "spirit varnish"), by moistening a rag with denatured alcohol and testing in an inconspicuous area; if the alcohol softens or dissolves the finish, it's shellac.

 

In my book, a varnish is a transparent protective coating. Usually made with resins or gums dissolved in a solvent. A spirit varnish has the resins or gums dissolved in alcohol. An oil varnish has the resins or gums in an oil/turpentine base. An epoxy varnish is different again.

Yeah, that looks like a spirit varnish containing shellac.

 

There has been a lot of discussion over the years (centuries perhaps) about the term 'spirit varnish'. The problem is that both words in the term have fairly generic meanings.

'Spirits' often refers to alcohol, but not always - as in 'sprits of turpentine' or 'mineral spirits'. 'Varnish' is even more loosely defined - at it's broadest definition it's a coating.

So a spirit varnish could be any kind of coating made from something dissolved in alcohol or another medium.

Perhaps for the case in question it's more valuable to know if the finish dissolves in alcohol or not. If so, the finish could be padded with some methyl hydrate, but I would recommend that this be performed by someone with experience.

But before doing that you might try a formula used by the British Museum for cleaning and restoring finishes. I found it often helped with finish bloom.

1 part each of cider vinegar, turpentine and boiled linseed oil, with a little Japan dryer. Shake it up well, and shake it often. Run it in with a soft cloth. Then rub it off vigourously. Rub a lot as though you were trying to remove evidence that there was ever any oil applied.

If this doesn't help, you might get the finish padded.

 

Back to the question: yes you can do it.

Two ways that I know of. The first: make a paste of cigarette ashes and water. Put a little of this on your finger and rub. It will usually remove this.

Second. Since this is a very large area here's the method I normally use. In a bottle, make a mixture of one part linseed oil, one part mineral oil and one part terpentine(synthetic is ok). To that add two parts of denatured alcohol and two parts of water. Shake well. Put a small amount of this on a piece of 0000 steel wool. Work a small area at a time, rub lightly(you don't want to go through the finish) until it comes off. Then dry with a paper towel or soft cloth. Keep doing this until you are finished and Bob's Your Uncle. Caution: don't let this mixture just sit on the bass too long.

Shellac in alccohol makes a spirit varnish.

I recently bought a product here in Mazatlan called Tinta al Alcohol (or color in alcohol). When I opened the can it did not have the smell of alcohol, but of some kind of mineral thinner. I think it might have alcohol in it too because the smell isn't as overwhelming as mineral spirits. I put some over some seedlac and I was surprised to see that it disolved it completely in just a day of occasional shaking. Now I need to test it. It has yielded, I hope, a spirit varnish. I'm testing it now and it seems to be working ok. The tint or color is a deep brown and looks nice.

 

if i recall correctly stewmac makes this blush remover i have used to get rid of white water streaks from violins ive taken the top off of(if left there it leaves white marks, or if the water is too hot) so maybe give that a try, dont know where it went or id give it to you, couldnt hurt, i feel like cigarette ash would work better due to more carcinogens(spelling?) while cigars contain less of the harsh chemicals, plus are probably cheaper. theres far more experience on here than mine but just my 2 cents, good luck

 

http://www.stewmac.com/shop/Finishing_supplies/Repair_and_touchup/Blush_Eraser.html

seems like its for use in guitars, but for 10 bucks its worth a shot?