how aggressive can you get with air dried lumber in a kiln?

[hackberry jake]

I had a bunch of flooring at about 19% mc. I put it in the kiln two days ago and checked it today and it's around 13%. That seems too fast, so I turned off everything in the kiln and got on the Forestry Forum.

[hackberry jake]

The flooring is 3/4" thick and mixed hardwood.

[Den Socling]

If it's truly in the teens, you're not going to hurt it.

[Dan_Shade]

my understanding is that damage occurs at over 35% MC

[GeneWengert-WoodDoc]

You cannot do much damage at this low MC, except if you over dry.  Over drying means more cup, more brittle wood when machining, poorer gluing, darker colors, etc.

[hackberry jake]

Thanks fellas!

[Driftless]

I have a similar question that kind of goes with this thread.  I usually air dry all of my lumber (down to about 13%) and then bring in my shop to equalize.  I have had mixed results especially in the summer time. 

I have access to a hot air chamber (over a weekend) that is heated with electric heaters to 140 F.  I measured the humidity in the chamber and it is right around 6-10%.  This seems too dry to use as a kiln to finish off the air dried wood. 

Thoughts?  Seems like I could do more damage than good trying to use this chamber.  Would it be too much of shock putting room temperature wood right into a 140 degree chamber?  Maybe I should stick with my shop build DH kiln idea.  I only need a few hundred board feet at a time anyways.

Thanks! 

[GeneWengert-WoodDoc]

Dry wood can change temperature without any risk.  However, it cannot change humidity.  The relative humidity in a house is between 30% average in the winter heating season and 50% in the summertime.  This means the wood will be 6% to 9% moisture.  If you have 10% RH in your oven, that is about 2% moisture content in wood and is way too dry and will damage the wood.