Shop humidity

[Cliff Rohrabacher]

What's the humidity in your shop~??
What did you do (if anything) to achieve the RH you have~?

Mine changed this year when I built a pair of maple tongue drums and when they were moved to their permanent home the glue joints on cross grain failed.
The failed on the tops but not the bottoms.

So I got a couple April Aire Dehumidifiers and now the RH in the cellar and adjoining garage shop is about 53%. The cellar used to have it's own monsoon season that started around the end of January and ended in late December.

Maybe now my glue joints will last longer than a month.

[Kirk Poore]

Isn't there always a risk of failure with cross-grain glue joints? Unless the distance is small, the environment dry all year round, or grain expansion and contraction otherwise minimized (such as with quarter-sawn or extremely well-sealed wood), the difference between cross- and with-grain will always put a strain on the piece and thus risk cracking the wood or breaking the glue. The moisture difference in most houses over the course of a year can be quite large.

Using a dehumidifier may minimize the problem in moving projects from your shop to the house, but within the house the risk is still there.

Kirk

[Von Bickley]

What's the humidity in your shop~??

What's the outside humidity??????:D :D

[Dave Anderson NH]

I run a dehumidifier in my basement shop from about May 1 through the end of September and some years into October. I strive to maintain the shop between 40-50%RH during these months. During this period I typically remove anywhere from 1 to 2 gallons per day depending on weather conditions and the amount of rainfall. During the winter in NH, there is always very low humidity and even with an open pot of water on the top of the woodstove the RH rarely gets above 25%.

I have no problems with rust on tools unless I am dripping sweat and some of it lands on a steel or cast iron surface.:D

[Emmanuel Weber]

I run a dehumidifier too to maintain the humidity between 40-45%. In winter I run a small humidifier which bring the humidity up to around 30-35%.

[Cliff Rohrabacher]

Isn't there always a risk of failure with cross-grain glue joints?

Always. But when you shop is damp and the home for the products is dry you are guaranteeing wood movement and in my case lots of it.


the difference between cross- and with-grain will always put a strain on the piece and thus risk cracking the wood or breaking the glue. The moisture difference in most houses over the course of a year can be quite large.


And with tongue drums you have a mandatory ( and large) cross grain joint in four places.
I don't see a way around it.

[Cliff Rohrabacher]

What's the outside humidity??????:D :D

I live in New Jersey. The water table is about 30 feet higher than my roof. Even on the mountain where I am.

[Greg Sznajdruk]

Relative humidity is a pretty meaningless number. Since it indicates what the humidity is relative to what the air could hold.

The true measure of moisture is Grains Per Pound. There are 7000 grains per pound of air fully saturated.

Here is an example 50% Rh at 50 degrees and 50% Rh at 70 degrees which is wetter?

50/50 is 26 GPP

50/70 is 54 GPP

Greg

[Andrew Williams]

50% in my basement shop with the DEhumidifier running in the summer. 35% or slightly less in the winter. So far the only joint I have made that has come apart was a cross-grain joint on a pine box. Not counting seams opening up on my 1930s Czech bass.

[Jim Becker]

My shop humidity is whatever it is outside, more or less. I've never had a problem with it since moving here in 1999. Never any rust on my machines unless someone is stupid...and I haven't had any strange wood movement issues. A/C only gets used for personal comfort when it's very sticky outside and that's the only dehumidification I have.

[Cliff Rohrabacher]

Relative humidity is a pretty meaningless number. Since it indicates what the humidity is relative to what the air could hold.

I'm not married to any measurement scale. However RH is a meaningful number since the amount of moisture that the air can soak up is very relevant to the amount of moisture that your wood may be soaking up.

However I ain't neer seen me no Grains Per Pound meter till you posted and I went googling to see wot deys do bees.
Exotecks model is $250.00 from Grainger. I have a RH meter that's about $20.00 I'm sticking with RH.


So it may be more accurate but ~ ~ ~ ~ ~ ~

[Gary Keedwell]

I keep one dehumidifier running in my basement on the wood storage side. Seems to stay between 50-60%. I did alot of sealing and painting down there and it seems to help. At least it doesn't smell like a basement.:rolleyes: :D
Gary K.

[Greg Sznajdruk]

I'm not married to any measurement scale. However RH is a meaningful number since the amount of moisture that the air can soak up is very relevant to the amount of moisture that your wood may be soaking up.

However I ain't neer seen me no Grains Per Pound meter till you posted and I went googling to see wot deys do bees.
Exotecks model is $250.00 from Grainger. I have a RH meter that's about $20.00 I'm sticking with RH.


So it may be more accurate but ~ ~ ~ ~ ~ ~

As in my quick example 50% Rh doesn't tell you how wet the air is. When the temperature changes and the Rh stays the same it is possible that the air could contain twice the moisture.

As far as rust is concerned the amount of moisture in the air is not an indication that your cast steel surfaces will rust what you need to determine is the DEW POINT. The Dew point is the temperature at which moisture in the air will condense on a surface.

50% Rh @ 50 degrees = 26 GPP Dew point is 32 degrees

50% Rh @ 70 degrees = 54 GPP Dew point is 51 degrees

In the second example any surface that reaches 51 degrees will condense out water from the atmosphere.

As far as what wood would absorb from the air you get into calculating THIRST. But thats another story.

Greg

Greg