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I built a guitar for a friend and gave it to her with an oasis soundhole humidifier. With time, I guess the humidifier was leaking from 1 of the seams and water was dripping into the interior of the guitar. Everything seems to be solid with no effect on the glue joints, just some water staining inside on the lower back and the tailblock and area around it. I don't think there was anything wrong with the humidifier that was not caused by the way it was handled. The problem is that I am starting to see some spots that look like mold is forming where the water staining is. There is no moldy odor, at least not yet. This baffles me because I live in the desert and have to use a humidifier. Not sure how mold would form in this dry environment. So the question is, how to kill the mold without damaging the guitar. Wouldn't you know this is the best guitar I have ever built. Thanks for any ideas, Wendy

Forgot to say that the leakage occurred almost a year ago and the guitar is now completely dry.

I had similar problems. I now put the humidifiers in the case, not in the sound hole. I do not know if it is completely stopped.


The first instance was that I used a Dampit in a Kohno 30. It turns out that Kohno singed with water soluble ink, and so now you need special lighting to prove the label was signed. Also, the label continued to develop what looks like mold spots. I have seen these spots on other Kohno labels.

I would wipe the area with a rag dampened with alcohol. If you want to be a bit more aggressive, scrape the area a bit and this should remove any stains and any remaining mold growth.

Thanks Barry, I might be able to reach some of it, but it's a small soundhole and I don't think I can reach all the way to the tailblock. I thought about spraying a dilute bleach inside, maybe alcohol would be better. Scraping is out of the question. I also don't want to change any of the brace dimensions since it is the best sounding guitar I will probably ever build

I'm wondering if anyone knows of a way to fumigate it to kill the mold, like they do with old furniture or books.

If you know anyone who owns an ozone generator that should kill it. Be careful with those things, though-it dissipates quickly but ozone is very toxic.

Wendy, whenever I have had to kill mold on wood, I have used 20 Volume Hydrogen Peroxide that hairdressers use to bleach hair. Works great and hasn't harmed the wood so far. Wear rubber gloves, dab it on or wipe with a cloth, then let it air out for a short period of time.

Bob

Thanks Bob. Just found it locally and will try it this afternoon. I have some long swabs that I should be able to reach the tailblock with. So It's OK to just leave it on there and air dry?

Ditto on the Peroxide solution. Just dab it on and let it dry. You don't need to go crazy with it...just dampen the surface

"I thought about spraying a dilute bleach inside"

That would also probably have worked fine. Even a fairly strong bleach solution shouldn't hurt if judiciously applied, and it will kill most molds.

Got a really good look inside the guitar this weekend with a light inside and there is mold spore in nooks and crannies where I will definitely not be able to reach without taking the back off. It looks like my only options are to spray something or have it fumigated. I am going to contact the conservation dept of the Musical Instrument Museum here in Phoenix. When I lived in Berkeley, the museum had a fumigation chamber available to the public for a fee. I worked with a conservation lab and we took objects there on occasion. I'll see what I can find out. Otherwise I have 3 choices; take the back off, spray a bleach solution, or spray a 20 volume hydrogen peroxide solution.

I would not hesitate to spray the peroxide.

Bob

Thanks Bob, that's what I have been hoping. I did email the conservation dept at the MIM. Curious to see if I hear back and what they have to say.

I prefer the dammit style humidifiers. Soak it then squeeze out the excess. Some skip that part. Never had leak, mold or staining issue.

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Its been a while since I put this out there and I never did anything about it. Yesterday I finally went and bought the 20 volume peroxide. When I looked in the guitar I see that the mold has spread and it is in numerous areas that I definitely can not reach even with a long swab. I am reluctant to spray liquid inside the guitar and there is now mold also along the fan braces on the inside of the top. Difficult areas to even reach with a spray bottle. I have seen some aerosols on Amazon that are supposed to kill mold. My idea is to spray an aerosol in the guitars and quickly seal up the soundhole and let it do its thing. Does anyone know which aerosol mold killer would be the least harmful to the guitar and do the best job killing the mold?

Maybe you could directly contact a world expert builder and restorer, such as R E Brune, with the question. He is a nice guy and I think he might offer advice.

I have a perhaps paranoid worry that the air in the guitar would reject your effort to uniformly spray into the cavity.

I used to work in the mold remediation industry. Although they will kill mold, the problem with a solution of peroxide or even bleach is that they include a lot of water. You do not want to be saturating the inside of a guitar with water. That could lead to swelling or cracks. Also the water could even allow the mold to grow more. The reason I recommended using alcohol is that there is not much water in it so these problems are lessened. Alcohol can definitely kill mold.

I had an 1970 Koa Martin with a similar problem. The guitar looked like it had been stored in the attic for 30 years and had gotten soaked with water a few times. The mold was very heavy inside the guitar and had even penetrated and discolored the back inlay strip. I had to remove the back to reattach the braces anyways, which had all come loose. While the body was open, I removed the mold by scraping every surface of the inside. What a mess. It is still sitting on my workbench.

I think that sealing the sound hole is not useful and only keeps things wet. Whatever is sprayed in contact with the mold is all that will react. Just my thoughts.

20% hydrogen peroxide is not as innocuous as the ordinary first aid stuff from the drug store. Take appropriate precautions if you use this or any other lethal spray.

Barry, I really don't want to remove the back. Are you recommending rubbing alcohol? Or denatured/Everclear? I really really really don't want to remove the back. As I said in the original post, when I worked in the art restoration field in the SF area, the museum had a fumigation chamber that the public could pay to have objects and art fumigated. I have not found anything like that here, but was hoping for something more gaseous that would fumigate the interior. My mention of sealing the soundhole would have been to keep the fumes in and give them a chance to work, not to close it up with liquid or dampness in there. Do you think it would be worthwhile to call a mold remediation company?

No, don't call a mold remediation company. They have no clue about guitars.

Either rubbing alcohol or denatured alcohol will work. The best way to apply it is to rub it on with a small soaked cloth. You could have the cloth on the end of a stick to reach the areas you can't reach with your arm through the sound hole.

The reason that swabbing it on will work better than spraying is that the swabbing action will roll the fungus around in the alcohol which will rupture the cells. It would be best to do a little area then let it dry out. If you get the wood soaked, the alcohol could penetrate through to the finish which could damage it.