Help!! Mold in the solar kiln

[Joel Eisner]

I loaded the second charge in the solar kiln 3 weeks ago.  The kiln design is the standard wood magazine / wood web design.




It is loaded with all southern yellow pine that is green.  It was cut over a several week period and loaded as it was cut (potential first problem).  About 1/3 of the boards have mold formation and I am not sure if I should increase the air flow and the expense of temperature or increase the temperature at the expense of air flow.

It is all 4x4 boards that will be planed down for floring.  Staining is not a concern since we have a blue stain already on the timber frame etc.

For the first week I used an extra horizontal baffel that restricts the recirculation of air so there is a single pass of air.  This does not allow the temps to rise up much.  I removed the baffle and now the temps are starting to get up about 104 deg or so with the vents cracked a few inches.  The MC is going down and ranges between 27 % and 15% depending upon the board.  Obviously the lower MC boards have no mold.  We are 3 weeks into the drying.  Should I just hold tight and let the temps get up to kill the mold?

The kiln, loaded with 1000BF of air dried SYP over the winter got up to 120 deg and dried the wood to about 6-8 % humidity.

I am in NC.

Thanks

Joel

[treecyclers]

I get mold on my Ponderosa pine when I have insufficient airflow to get the initial moisture out of the wood, most often when it's "doesn't know it's dead yet" green, and I stick and stack it in the shed.
Even with a 15% ambient humidity in the air, I still have to ensure that I have ample airflow to keep that from happening.
I might suggest that you crank up the airflow to better enable moisture removal, at least initially, to stave off the molding. That should help.
Then, as the MC comes down, crank up the heat and get it to drying more efficiently.
JMHO.
Superdave

[Paschale]

Hey Joel,

This is the first post I've noticed from you--welcome to the forum, even if it's 38  posts late.  You byline intrigues:  building my own home from timbers from the land sounded like a good idea to me.   8)

How's it coming?  Have you built your house, or still in the progress?  Or...have you already talked about this in some other corner of the forum?  I'd enjoy hearing about your experiences.  I'd like to do the same thing with a cabin up north.

[chet]

I agree with Dave, ya need more air flow. I see ya added the secret extra baffle too 

[beenthere]

I'm gathering you meant 4/4 boards, not 4" x 4" as it is flooring.
If you want to stop the potential stain from the mold, I'd remove it and spray a light mix of bleach and water on it and then stack it back in the kiln. Otherwise, if some staining isn't going to deter the looks of your flooring, I'd finish drying it as you are doing.
If stacking like that in the future, a light spray of bleach/water mix would likely help a lot to keep this from happening.

[Ianab]

You have basically got to the point where the mould is going to stop anyway, so carry on. Pine needs lots of airflow to carry away the moisture which migrates to the surface easily. So it dries quickly, but unless you are moving / venting that air you can get mould. Maybe you need a couple more fans in there? I think more airflow / venting in the initial part of the drying untill you get down to 15-20%. Then close it up and let the temp come up to finish the drying and set the pitch a bit at the end.

Cheers

Ian