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Acid fumes are a real hazard and not to be dealt with lightly. I obtained some acid cartridges for my respirator and used rubber gloves and boots. I was doing my garage floor, so I opened the garage door and just hosed the acid out onto the driveway.

Doing it in a basement would be more difficult. You could neutralize the acid with a bunch of baking soda and water, then pump it out with a submersible pump and a squeegee.

I've have one of the Frigidaire units that cost around $220. Midwest living with indoor RH running around 25% in the winter and 75+% in the summer. Shop is on a concrete floor with no vapor barrier. I don't find the RH indicator on the machine to do much of anything, seems to always read around 50%. So if I set it at 45% is will run constantly. I have 3-5 different humidity meters running, both analog and digital in the shop and the house and when moving them around they are always in the same 10% range. Having spent many years in a certified lab splitting hairs, my house and shop isn't like that and I don't think it needs that kind of accuracy, RH about +-5% or so, is good enough for me.

I ask myself, "How many guitar owners live, work, travel, and play in a lab?" I don't know any.

I like to build in low RH when I can, especially the boxes, that puts my instruments in expansion mode just about all the time. IMO, taking a 50+% built box and subjecting it to 25% is where most of the problems lie.

Spring and summer I can keep the shop in the 45-50% range and that's about the best I can do. So I try and build boxes in winter and necks in the summer.

If you don't have that kind of flexibility, more drastic measures may be necessary. Like a hermetically sealed shop in summer humid locales.

When the ambient RH is running high, I've found I can keep shop RH around 45% running the DeHumidifier about 3 hrs in the morning and 3 hrs in the evening. Running it longer doesn't seem to make much difference so I put it on an automatic timer from 9 till noon and from 7 till 10 at night.

Works for me and doesn't spin the meter all day and all night.

Brian

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Brian R, Wood Mechanic
N8ZED

For sealing the floor, I wonder if this would work. Years ago when I put down tiles on a concrete floor, the directions required sealing with something that looked to me like the active part of latex paint, i.e., just clear "glue". No acid wash and no fumes.

I currently have 6 dehumidifiers.
Three work, three don’t

The ones that work were all puchased from garage sales and are 20-30 years old. They work great.

So, an alternative exists. Watch craigslist and garage sales. I think one of them was $8 and it is what is doing the shop right now.