How much water to add for conditioning

[JoshNZ]

Hi guys,

Quick question I'm wondering how much water you add to your kiln at the end of a cycle to condition, approximately. I've finally built a mister which works really well, no puddles etc but I'm amazed at the amount of water needed to add to get a humidity lift.

The contraption is in a photo below and the screenshot is of the charts, I assume what I'm seeing is the bottle dry up at 82% humidity then the drop again is the wood sucking it back out of the air, that was with 10L added - which I thought was a lot but maybe it's not. I was shooting for 85% to reach an equilibrium of 17%, there is a load of cedar in there set to be resawn for weather boards.


https://youtu.be/Qaeo9EIMncs?si=U8YJ_vLWuDHJwiUT

[K-Guy]

I recommend 5 gallons below 2000 bf and 10 gallons for 2000-4000 bf.

[JoshNZ]

Wow alright, that's a lot more than I expected! Should've ran a water line when I had the trench to it open hah

[Ianab]

It takes very little water (added or removed) to change the humidity of the air, but the wood can hold a LOT more. So to change the MC of 1,000 kg of wood by just 1% would need about 10 kg of water. 

As you suspect the wood will be absorbing the moisture from the now humid air in the kiln, That drops the  RH until everything comes back into equilibrium.  So basically you need to keep the RH at that 85%, by adding more water, until the wood settles to that level as well. 

[K-Guy]

What I recommend isn't enough to change the moisture content much, if at all but it should relieve tension in the wood if you have case hardening.

[jimF]

To be effective you need to add 2-3% to the surface layer very quickly. Adding slowly to the full thickness will not relieve stress. so hit hard with as high of RH as you can get initially.