Setting pitch in a solar kiln.

Dave Shepard · August 31, 2014, 07:24:14 PM

Can it be done? I've got a bunch of nice EWP air drying at the mill yard, and I'd like to be able to dry it and set the pitch. I've seen too many times when someone uses air dried pine for something interior and the pitch pours out of it eventually.

Ianab · August 31, 2014, 07:43:30 PM

You will be able to set the pitch up to the temperature that the kiln can achieve. If the wood later gets heated to above that temp, the remaining pitch can still liquefy. But you can get a pretty good temp in a solar kiln on a hot day, with the vents closed up, and that temp wont harm a load of dry wood.

So I would suggest a day of "baking" at the end of the drying process. Close the vents and just run the fans. You may not get things to the same level as a high temp commercial kiln can, but the pitch wont liquefy again in normal conditions.

Ian

Dave Shepard · August 31, 2014, 08:00:59 PM

I'm thinking I might set up a kiln on trailer, so I can move it near my OWB. How hot can I run a Modine hanging heater? Do you think they will take 160°? I was thinking of having several solar kilns near the mill, and then moving it to the trailer for finishing. Also, any hardwood that I would dry I could store in the kiln, as I don't have a building to keep dry lumber in yet.

GeneWengert-WoodDoc · August 31, 2014, 11:15:50 PM

Indeed many kiln operations have a separate chamber for stress relief and use the same chamber for setting the pitch. For EWP, no less that 12 hours at 160 F is suggested for 6/4 and thinner. Longer for 8/4. A solar kiln may reach 160 F for a brief period (many will not reach that except in a rare instance), but the lumber will not get this hot in just a few hours. I suggest that you need another chamber.

Den Socling · August 31, 2014, 11:23:41 PM

Gene,

Did you notice the request for info regarding education above?

Den

LeeB · September 01, 2014, 11:19:15 AM

@GeneWengert-WoodDoc I think Den was refering to this.
https://forestryforum.com/board/index.php/topic,77452.0.html

red oaks lumber · September 01, 2014, 05:10:50 PM

dave
the modine can handle the temp, the boiler will need to be set closer to 200 deg.to keep pulling heat off to raise the temp in the kiln.

YellowHammer · September 01, 2014, 05:52:01 PM

I can't consistently sterilize in my solar kiln, although it regularly hits 145° F to 155° F; I just don't think it stays at the elevated temps long enough. I would think that some kind of auxiliary heat, as you are contemplating, to keep the daytime temps elevated at night would be the solution to set pitch.

YH

Dave Shepard · September 01, 2014, 06:59:48 PM

I guess if I'm going to build a sterilization chamber on a trailer so I can move it to my house, I might as well do the whole load there. I could build some small buildings with some solar capacity to keep the dry lumber dry. I don't see myself needing to dry a lot of lumber right now. Maybe a 4'x4'x16' lift of pine would be the biggest package. Maybe make the chamber long enough to put two 8' lifts in side by side.I have a 20' gooseneck trailer that I could build a chamber on. I could even make the chamber removable.

pineywoods · September 01, 2014, 07:04:38 PM

I can't speak for other solar kilns. They may not get hot enough. Mine does.
8) 8) 8)

Dave Shepard · September 01, 2014, 07:06:41 PM

You might have a latitudinal advantage. Hmm, spellcheck liked latitudinal, but not spellcheck. :D I didn't know it was a word.

YellowHammer · September 02, 2014, 10:02:57 PM

Quote from: pineywoods on September 01, 2014, 07:04:38 PM
I can't speak for other solar kilns. They may not get hot enough. Mine does.

True enough, mine is the classic Va Tech design with 2 layers of clear poly roofing material, Pineywoods uses a corrugated metal collector attached to the rafters, I believe.

I also agree that the latitudinal and regional effects play a role in the amount of usable heat generated per collector area, especially in the winter.
YH

GeneWengert-WoodDoc · September 03, 2014, 10:05:41 AM

It will be nearly impossible in a solar kiln to reach the temperatures required for the length of time required to set the pitch well. Auxiliary heat, including a DH compressor, can be used to achieve the temperatures, or , as suggested, an auxiliary chamber can be used.

When setting pitch or sterilizing, it is the temperature in the core of the wood that is the key, not the air temperature.

Regarding storage of dry lumber, a tight building (use plastic vapor barriers, especially for the floor) that is dark colored walls and roof, so you get some solar heating, is all that is required. A small fan to slowly stir the air is also required. No need to have clear panels.