Drying wood at different stages in solar kiln

[Panovak]

Is there anything wrong with adding green wood to a batch of drying wood in a solar kiln? I'm designing my kiln now and am wondering about sizing. For instance if it's bad to add green lumber than I'd build two smaller ones. I'd prefer to build one single kiln otherwise.  Thanks

[Stevenjohn21]

From my understanding, you should try to match species as best you can so when it's  drying, it'll lose its moisture at comparable rates. Same goes with say air dried lumber and green lumber. Again, from my understanding, as moisture is coming out of the green wood, the partially dry wood is going to soak up that moisture and take longer to dry.

I will say, if you plan to cut a lot of wood year round then I'd build 2 big kilns.
I built 1 big one thinking it would be plenty big enough and you'll be amazed how quick it fills up especially if slabs are not all uniformed in size.

The drying masters will be along shortly I'm sure and explain way better than I can ever do.

[scsmith42]

Hypothetically speaking, adding green wood to a partially dried charge in a kiln can result in higher RH% inside the kiln, causing the drier lumber to absorb moisture.  Repeat cycles of this can result in surface checking from the drier lumber swelling and shrinking.

In reality, solar kilns are very forgiving and their typical daily cycle results in a high variance in RH%.

I operate 4 solar kilns in addition to my Nyle, and prefer to load them with similar MC% charges and then keep them closed up until they are ready.  Sometimes I'll add air dried lumber into a partially dried charge.

Keep in mind that every time you have to touch the lumber, you're losing $.  So if you build one kiln and are always having to reopen it, rebaffle it, etc, it may not be as efficient as alternating charges in two smaller units.

[doc henderson]

the other way is to air dry till there is room for another load.  I do think the solar kiln is the most forgiving with RH cycling up and down over every 24-hour period.  Add the next load with one that is drying, my save time on that load, but add time on the first load.  there are so many pounds of water to remove and if you throw more wood in that is green (think pounds of water) it will take longer for the load and may cause some wood to back up.

[Panovak]

Thanks for the replies. I think Ill start with a small kiln, around 800 - 1000 bd ft. I suppose the other advantage to multiple smaller units is that you can improve the design a bit each time. I found a bunch of really nice double wall polycarbonate for dirt cheap. The local massive nursery was replacing their panels!