Heavy white water stain

[dscheck]

Hi , I’m looking for any advice on how to remove a heavy white water stain from an all mahogany guitar. The guitar in question is a very nice Martin 50’s vintage 00-17. I assume it has a nitro finish. I’m not a luthier, having only built one guitar plus a few easy repairs, but I made my living as a woodworker so have done a lot of finishing. The goal here would be to remove as much of the white stain as possible while not damaging the finish. This is a heavy stain from someone setting a glass on the guitar (!) not a light haze beneath the finish. It’s been on there while not sure how long exactly but years not days, Thanks for any advice.
David

[Edgar Poe]

White tells me it is in the finish only, it has not traveled to the wood itself. I can't recall the product but there is one for furniture that will draw out finish water stains. If it's all the way to the wood, that's a different story all together.
Some will use and iron with a cloth, or a hair dryer on low. Check link below.

https://tinyurl.com/y46xa36s

Ed

[John Arnold]

Denatured alcohol is the first thing I try. Wipe it on in several applications, but do not continue to rub, since alcohol will tend to soften the lacquer somewhat. You may end up with blushing on the surface that will polish out. Let it dry completely before polishing.
If that fails to remove it all, I next use lacquer retarder. Retarder will soften the lacquer more than alcohol, which means it may take several days for it to harden back up. Do not attempt to manipulate the surface until it does.

[NotALuth]

I’m going to disagree with, the vastly more experienced, John Arnold and suggest you first attempt to remove the water stain with water!

However, not ordinary tap or bottled water, but deionised water (aka demineralised water).If it is a true water stain then it will consist of minerals that got left behind when the water evaporated (like when you let a saucepan boil dry). Deionised water has had all its minerals removed and will readily dissolve any it can find. Surely worth a try?

As ever, especially on an old nitro finish, proceed with caution whatever route you take.

Wishing you success,
Clive.

[B. Howard]

Pictures may help as not all water stains are equal.

A slight haze may be cleared up with DA but the surface will still likely need rebuffed. Heavier marks may be removed with retarder by a good guitar restoration shop.

Things like crazing of the film or burst finishes make this much more difficult.

But based on your description "This is a heavy stain from someone setting a glass on the guitar (!) not a light haze beneath the finish."I am going to say that this mark is permanent and only refinishing will restore it..... You may well find a dark mark in the wood under the white finish once it is removed.

[runamuck]

Here's one other idea that works with some lacquers some of the time.

Apply Vasoline to the stain and keep your eye on it. If it works, be prepared to wipe it off just before the white is almost gone. If you wait too long, it can darken the area too much- if it works, which it may not depending on the lacquer and other variables I've never understood.

[Frank Ford]

Originally Posted by John Arnold

Denatured alcohol is the first thing I try. Wipe it on in several applications, but do not continue to rub, since alcohol will tend to soften the lacquer somewhat. You may end up with blushing on the surface that will polish out. Let it dry completely before polishing.
If that fails to remove it all, I next use lacquer retarder. Retarder will soften the lacquer more than alcohol, which means it may take several days for it to harden back up. Do not attempt to manipulate the surface until it does.

Yep, that would be my approach, too.

[dscheck]

Thanks for all the help with this. Using denatured alcohol worked well, took out the heaviest of the white stain. There was a little blush below the surface left. I tried retarder on that and the last of it disappeared. I think I sprayed it a little heavy and there are some light ridges left in the lacquer finish. Would it work lightly hit it with micro mesh to take out the ridges and then polish to blend to the rest of the top? Thanks again

[Howard Klepper]

Originally Posted by NotALuth

I’m going to disagree with, the vastly more experienced, John Arnold and suggest you first attempt to remove the water stain with water!

However, not ordinary tap or bottled water, but deionised water (aka demineralised water).If it is a true water stain then it will consist of minerals that got left behind when the water evaporated (like when you let a saucepan boil dry). Deionised water has had all its minerals removed and will readily dissolve any it can find. Surely worth a try?

As ever, especially on an old nitro finish, proceed with caution whatever route you take.

Wishing you success,
Clive.

This will not work. The stain is not minerals, and deionised water will not dissolve it--it isn't on the surface.

With a years-old mark, the water is long gone. What is left is lacquer that is full of micrscopic air pockets (these create reflections of light that make the area look white) that has to be redissolved. I would skip the alcohol (but you can try that--it is safer), and go right to lacquer thinner (which is more likely to do the job than alcohol). I prefer that to retarder, since it won't soften the finish as much or for as long. The trick is not to let it soak the finish and not to leave a rag mark. The way you do that is to use a clean flat white cotton rag and make it damp with thinner but not wet--you don't want any drops or pools left behind. The next thing is to keep the rag moving, starting before it touches the surface, and to just touch the surface--don't press. Lift the rag while it is still moving. One or two seconds is long enough. You should see a substantial if not complete change to transparent almost instantly. Then let the finish harden for a day and do it again if it's not completely clear.

[John Arnold]

Sounds like you did well. Retarder is powerful stuff, and it is easy to overdo. The ridges can be leveled and polished out; just go slow to avoid creating bare spots.

[redir]

I've used a product known as Blush Eraser for this type of thing, perhaps that is the same as retarder but it works great. I never alcohol but it does sound a lot safer.