Jump to content
Maestronet Forums

Dangerously Low Humidity


David Burgess
 Share

Recommended Posts

15 hours ago, Rue said:

It's not really all that simple:

What room humidifier works best?  Yes it depends, but there are pros/cons associated with any of the following:

1. Passive (which I'm trying this year, since one of my guitars decided to have issues)

2. Evaporative 

3. Cool mist

4. Warm mist

5. Ultrasonic

6. Vaporizers

Despite what the advertising for any particular type may claim, ALL of them have to be refilled regularly and kept very clean - or you'll be breathing in a bunch of bacteria and whatnot...

1. This is not truly passive, since it relies on heated forced air from the furnace to make it work. And water evaporation always involves a consumption of energy. In your case, the air coming into the room from the duct will be colder with the humidifier, than without.

Yes , some forms of energy are less expensive than others. I'm using electricity to boil the water into steam, which in my area, costs about six times as much per BTU as as natural gas. But I'm still only spending around an average of six dollars per month, maybe five months per year, to keep my shop humidified to 40 percent, and the rest of my house humidified to 32 percent during our coldest periods. The ease and low maintenance are worth the thirty bucks per year, to me.

3 and 5: "Cool mist" and "Ultrasonic" are basically the same thing. Both will cool the air, (which needs to brought  back up to the original temperature by some expenditure of additional energy) and both have the potential downside of dispersing mineral dust all over the room, if ones water source has some mineral content. I make dust anyway, so that part doesn't matter to me so much, but mineral dust is much more abrasive on cutting-tool  edges than wood dust.

Rue also wrote:

"Despite what the advertising for any particular type may claim, ALL of them have to be refilled regularly and kept very clean - or you'll be breathing in a bunch of bacteria and whatnot..."

Yuck growing in a humidifier is certainly a concern. Even if an evaporative pad or media will not support mold growth itself, it will become contaminated with organic material in the air which is forced through it, and then you've got a yuck-growing farm. That's the main reason why I prefer the steam type. There isn't room air being forced through it; there is no yuck-culturing media; and the moisture it emits ends up as distilled water which has been sanitized by boiling.

On refilling regularly, maybe yes, maybe no. Central furnace humidifiers are usually hooked up to an automatic water supply, and some types which do a single pass with the water , then put it down the drain (rather than recirculating it) only require service once per season.

On my cheap steam vaporizer, I've rigged up a refrigerator-type water supply, and a drain (the height of the drain installed on the side of the reservoir controls the water level), and it can usually make it through the entire humidifying season without requiring any attention. Totally automatic operation. Been using this for about ten years now.

 


 

14 hours ago, DMartin said:

I fully agree with your 30 second assessment. The hot air systems I encounter are very harsh. If you (or a violin) are near a vent your are periodically breathing air that is drier than the room average.

And sometimes more moist than the room average. But overall, I'll wager that a forced-air system distributes both temperature and moisture much more evenly than other heating methods.

 

Link to comment
Share on other sites

  • Replies 98
  • Created
  • Last Reply

Top Posters In This Topic

I got myself a cheap mini vaporizer (a $10 eBay purchase) that I thought would fit in the UV light box, and it turned out to be just that. I've resorted to leaving a pan of water with a computer fan blowing on it inside the box. After a three-week marathon varnishing session my neck angle has risen over a mm. It is what it is, at least for now. I'm guessing once I leave it strung up and the humidity returns it will eventually creep back down. I built an extra .5mm or so of elevation in the neck to account for settling, looks like that may have been unnecessary, time and experience will tell.

Link to comment
Share on other sites

20 minutes ago, sospiri said:

Even though I was joking,  I still need an explanation because my measurements show that my spruce billets gain weight in winter and lose weight in summer.

If you monitor RH you will find your billets weight will rise and fall with the RH.  Is your wood stored in an outbuilding without climate control?

Link to comment
Share on other sites

26 minutes ago, Jim Bress said:

If you monitor RH you will find your billets weight will rise and fall with the RH.  Is your wood stored in an outbuilding without climate control?

The measurements were taken indoors.

I have never lived in a house with humidity control or air conditioning of any kind.

Link to comment
Share on other sites

19 minutes ago, sospiri said:

The measurements were taken indoors.

I have never lived in a house with humidity control or air conditioning of any kind.

I don't remember where you live. I'm thinking in the UK, but I can't remember why. Anyway, if you look at the monthly annual averages of RH in your area, it will should match your weight trends. Here's an example graph even if my recollection of where you live is way off.

Average relative humidity in London, United Kingdom   Copyright © 2020 www.weather-and-climate.com

Link to comment
Share on other sites

15 hours ago, Jim Bress said:

I don't remember where you live. I'm thinking in the UK, but I can't remember why. Anyway, if you look at the monthly annual averages of RH in your area, it will should match your weight trends. Here's an example graph even if my recollection of where you live is way off.

Average relative humidity in London, United Kingdom   Copyright © 2020 www.weather-and-climate.com

It varies from 70 to 100 all year round. Rainfall patterns and wind direction are unpredictable. 

North weaterlies coming from the arctic are cooler and drier  South westerlies coming from the Gulf of Mexico/Caribbean are warmer and wetter. 

I weighed 2 Simeon Chambers low density spruce billets over 2 years and the weight was as low as 690 Summer and up to  715 in winter.

 

Link to comment
Share on other sites

On 2/19/2021 at 5:16 PM, milkpowder said:

One would assume that because there is a higher AH t in the atmosphere at 50%RH 70°F than 50%RH 0°F that the wood would also contain more water. 

 

On 2/19/2021 at 5:27 PM, David Burgess said:

I know. Weird stuff, right?

So what is happening? Is there more evaporation in warm air and more condensation in cold air?

Link to comment
Share on other sites

10 minutes ago, sospiri said:

So I'm getting 6 percent EMC in summer and 9 in winter. Hence my question about evaporation and condensation.

It isn't an evaporative/condensation process. It is an absorption/adsorption process. The equilibrium moisture content is going to be dependent on the properties of the specific matrix (wood).

Link to comment
Share on other sites

21 minutes ago, GeorgeH said:

It isn't an evaporative/condensation process. It is an absorption/adsorption process. The equilibrium moisture content is going to be dependent on the properties of the specific matrix (wood).

But that is dependent on the moisture that surrounds the wood is it not?

Recent experiment. I placed a box of salt on a heater until it was bone dry and then placed it in another part of the room. It absorbed a lot of moisture and the surrounding area was very damp too, including a bridge and pieces of paper, which weredry the day before.

Link to comment
Share on other sites

11 minutes ago, GeorgeH said:

Yes, and also time to reach equilibrium (steady state) with the surrounding moisture.

In my spruce measurements, the absorption/adsorption was slow, but a marked difference from January to July.  

The difference was not structurally significant though, only 3%.

In a different environment, no doubt it would be a cause for concern. 

Link to comment
Share on other sites

4 hours ago, GeorgeH said:

Any ideas how long it take for a "dry" violin to reach equilibrium hydration at (for example) 70ºF and 50%RH?

Any ideas how long it take for a "hydrated" violin to dry out at (for example) 70ºF and 0%RH?

About two days for the plates, a bit more for the blocks, neck and fingerboard. About 1mm a day.

Link to comment
Share on other sites

2 hours ago, GeorgeH said:

Thanks - do you think it dries-out at the same rate?

Yes, I Think so. But in reality the changes take more time as the RH usually does not change as abrubt and stay as stable over time as in controlled laboratories.

If there is free water involved, that dynamics has to do its thing before the bound water can gradually change in the wood at the end. That is free water will feed the bound part until its gone and the bound water can diffuse. 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

  • Recently Browsing   0 members

    No registered users viewing this page.




×
×
  • Create New...