Humidity & dehumidifiers

Discussion in 'Luthier's Corner' started by pnchad, Dec 18, 2005.

  1. pnchad

    pnchad Supporting Member

    Nov 3, 2005
    Help. I have another thread going 'Building a Shop' and got a ton of great info. But, one issue keeps coming up and worrying me.

    Hi, my name is Paul. I live in south Florida where the humidity is often 80+ percent for weeks at a time.

    How stable is the stock usually available? (I know it varries greatly, but how much change might I expect, mahogany, maple, ash, etc??).

    Also the issue of finishing in this environment??

    Anybody have first hand experience with dehumidifier room units? How much power do they consume and is it cool to leave it on for days at a time? How well do thy work? There are many on the market for $300+/- that claim to handle 50 percent per day/1100 sq. ft. That seems questionable to me. :eyebrow:
  2. pnchad

    pnchad Supporting Member

    Nov 3, 2005
    I guess no one has a dehumidifier, eh?
  3. Scott French

    Scott French Dude Supporting Member

    May 12, 2004
    Grass Valley, CA
    I have an inexpensive one that adds and removes water from the air. I forget the brand right now. I set it to 50% and it keeps the place around 47% (numerous electronic humidty guages around the shop). I have it running quite often but not 24/7. I'm sure it burns a ton of energy but I can't say exactly how much since my shop it at my house and I have roommates who constantly run space heaters, leave lights on, etc. During the summer I can control things by leaving doors and windows open at the right times.

    The thicker the stock the less the humidy changes will effect you.

    High humidity is going to cause certain spray finishes to blush.

    I'm not sure I know exactly what "handle 50" means, buy my shop is much smaller and running full blast it wont drop more than 10-15% in a few hours.
  4. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    I've got a dehumidifier in my basement. I can't tell you what RH its set to, it's just set to "dry". It runs (in my climate) about an hour or two a day in the summer, and an hour or two a week in the winter. In florida I would gues it might run quite a bit.

    No problem leaving it plugged in, and running when it needs to.

    Power consumption wise, a dehumidifier is basically an air conditioner that blows the cooled/dried air back over the hot-side heat exchanger to re-warm the (dried) air. So figure a similar power usage.
  5. pnchad

    pnchad Supporting Member

    Nov 3, 2005
    Yea, I will try talking to a few product support people. It's very hard to say but I'd bet even a good one would have to run more than 12 hrs/day to even keep a 20' x 20' x 8' volume at under 70% and I'm not sure that's acceptable. :meh:

    Maybe a small drying closet for stock and storage would work?? :eyebrow:
  6. pilotjones

    pilotjones Supporting Member

    Nov 8, 2001
    One thing to keep in mind, which some people might overlook: if you're talking about dehumidifying a single room, or two, shut the door! If you treat the humidity-controlled area the same way you would for trying not to lose heat in the winter or air-conditioned cool air in the summer, you will cut down substantially on how much the unit has to run.
  7. I have a buddy who is a long time, full time professional instrument repairman in Florida. I got this story secondhand from him, but I trust him not to exagerrate too much!

    He realized early on that finishing in +60% humidity was going to be a problem, mostly due to the moisture getting trapped in the finish as he shot it. It created a very strong whitish haze ("blush"), and brutal stability problems. Early in his career, he found himself shooting coats of pure thinner or commercial "blush eraser" over his nitro to free the trapped moisture. This worked well enough once he got his spraying technique tuned up for fast, thin coats. It cost money and added time to his refinishing process, but it works most of the time.

    He tried a succession of domestic air conditioners and dehumidifiers, getting progressively larger and more expensive. Most of them worked well enough until he turned on his exhaust fan. The fan exhausted the dry air a lot faster than the a/c or dehumidifier could replace it, so his shooting sessions had to be very short, with a long period in between so the a/c or dehumidifier could get the air inside the shop (and later, the booth alone) back to an acceptable humidity. He would turn the unit on 2-4 hours before he intended to use the booth, then shoot for 15 to 25 minutes tops, then wait another two to four hours to shoot again. This worked fine for little jobs, such as finishing one instrument at a time, but to a pro this was unacceptable because the shooting window was way too short.

    He got a line on a big, industrial dehumidifier that was used and wouldn't break the bank. He installed it on the roof of his shop. It worked well enough, in that it could keep up with the exhaust fan, but it looked like a rusty old 1950's space ship and it sounded like the war of the worlds, and when it began to crash through his roof, he got rid of it.

    His neighbors started in on him about this time, and like many pros, he got forced into the use of water-based finish materials for most jobs. The finished product sounds, looks, and wears pretty well. It's probably a little safer for his respiratory system, and he stores non-flammables. Cost is a little higher, but not objectionable. His insurance premiums actually dropped a little!

    When he needs a nitro job for a particular customer, we worked out an arrangement where he would ship me prepped instruments and I would shoot clear coats only. He still has to get the color coats or bursts on himself, but this is manageable for him. He gets back instruments that need only the final rub. With FedEx prices, and dismantled all the bolt-ons, this is not a bad arrangement. I send him similiarly prepped stuff for him to shoot during my rainy season, and no money changes hands. We keep track of who's doing what, and it balances out pretty well.

    After thirty years in the business, this is where he wound up. There is equipment out there that will get your shop (or a well-sealed and insulated booth) where you want it, but keeping up with an adequate exhaust fan is the problem. Since the exhaust fan is so important for safety reasons, there isn't much you can do about that end of it. I am getting into the water-bases, and this might be your most practical option.
  8. garethjones


    Apr 8, 2011
    Dehumidifier will help you...

    Initial cost can be high but some energy efficient ones can save your money.

    They are also effective...

  9. baileyboy


    Aug 12, 2010
    I use a Comfort-Aire that allows me to keep the room at 50% RH and it does a pretty god job of it. I also put Zorb-It packets in each case-these release/add moisture to inside of case as needed. Hope this helps.
  10. gbarcus

    gbarcus Commercial User

    Jul 20, 2008
    Minneapolis & St.Paul, MN
    Owner of Barcus Basses