Kevin Koski

[#1]

Hi everybody. I hope all of you guys and gals that go through a lot of lumber are seriously thinking about building your own solar kiln. As explained in the previous blogs, it's inexpensive and easy to build. It's also a great way to utilize some of those yard trees that get cut into firewood. I saw an old timer that was cutting a 30" walnut tree into 16" sections last fall. I got there as he was just about done! Once you have your kiln built, you can sneak over into your neighbors yard and mill out his cherry tree you have had your eye on! You may even have it dried before he gets back from vacation!

I spent about $400 to build my 300 board foot kiln, and I built it right at the housing boom when building materials were almost three times the price they are now! The glass is easily obtainable from anyone that does home remodeling.

As you can guess, the solar kiln works best when there is lots of solar. This doesn't mean that's it's useless in the winter though. I can sometimes dry out a load through the winter months. I bet if you are anywhere but here, you can get a couple loads out, or more. I live in the snow belt region of NE OH. This means that Lake Erie generates it's own weather for us, like lake effect snow, lake effect rain, and always lake effect cloud cover! If you go through a lot of lumber in a year then you can build a bigger kiln, or air dry the lumber for a couple months before you put it into the kiln. You can easily double your kiln capacity if you air dry first, but please, I am on my knees begging you here, do not ever air dry maple unless you do it only in the winter. I want to cover this in another blog. We will go over air drying and how to do it right, and how to do it wrong. I have done it both ways, so I hope you can learn from my tragic mistakes!

You have your "green" lumber that had leaves growing on it a few days ago. Let's dry it! I personally keep my solar kiln lumber pile no more than 4' wide. Air flow through the pile is extremely important when drying lumber, and even more so when it comes to the solar kiln. There are days that the lumber doesn't get quite warm enough to dry, but does get warm enough to allow blue stain mold. If the air isn't strong throughout the pile it will grow, and ruin your lighter colored woods, and leave you some nice sticker shadows as a going away gift! This mold doesn't seem to be a problem with the oaks, cherry, walnut. Maple is horrible, and pine isn't any better. I have also seen it affect sycamore and poplar.

Keep your layers about 3/4" apart with your DRY sticks. No dry sticks? Then this should be your first load through your new kiln! Did I mention using DRY sticks? Use DRY sticks! If you like sticker shadows on your wood then use some green/undried sticks. Keep the board foot load to the 10 to 1 ratio of the glass collectors you have. I have 30 square feet of glass, thus I can dry about 300 bd ft of lumber in a load.

Let's assume it's summer. The sun is high in the sky, the birds are singing, and the Cleveland Indians have just traded away all of their good players. You have your kiln loaded up, and you kept a 6-8" space from the short wall to the pile. This space is for the air flow from the fan. If I have the room, I put as many concrete blocks on the top of the pile as I can. This helps keep the top layer from warping, twisting, bowing, and bending. If no room, then use your lesser grades up at the top. Crack all of your vents about an inch, or two, and let her run! Some of you southern guys may have to open them up more. My kiln never gets over 130 degrees in the summer. Try not to go over that, or you can cause checking, and honeycombing in your lumber. If it's still too hot after opening your vents, put a cover over part of your glass.

Plug in your big fan(s)and you should be able to feel the air through coming through the other side of the pile. All is good. I put my fans on an adjustable timer. In the summer, they are set for about 1 hour after sunrise to 1 hour after sunset. If I am drying maple I let them go an hour, or two in both directions. The fans are shut off at night, and this basically shuts down the drying. This is important as it allows the wood to relax and absorb some moisture back into it's surface. The process eliminates case hardening. You guys all know what that is I bet. When the wood pinches your saw, sometimes with dangerous results! This is caused from drying lumber too fast. If you shut the kiln down at night, you won't have this problem.

Buy yourself a good moisture meter. I don't think I am allowed to recommend one, or another on this forum. If your wood is higher than 25% moisture content (MC) then you want to monitor the drying daily. Try and keep the MC loss on the oaks to no more than 3% a day, on the maples, cherry, walnut, hickories, no more 7% a day. If you have your wood air dried to 25%, or less then just put it in the kiln, and take it out at 7%. You do not have to worry about MC loss in any given day. Why, you ask? Read my future air drying blog, and I will tell you!

The drying times for the maples, cherry, walnut, hickories, and most other species aside from the oaks, and elms is 2-3 weeks in the summertime .  For the oaks, and elms, double the drying time.  Double the times again for 8/4 lumber as the previous times are for 4/4.   Maybe better off air drying your 8/4 first for a couple months, or so. These are approximate times and will vary depending on the lumber MC, the weather, and your location in the USA.

In the summertime the solar kiln works just as quickly as an electric kiln.  The lumber is a big heatsink that absorbs the sun's energy all day long, and releases it at night into your insulated kiln chamber.  By the tme the sun comes up, and the fans start up, the load is still warm enough to commence drying right from the start. Conversely, in the winter, the lumber pile is a cold sink.  The short days, and long, cold nights ensure that the pile stays cold most of the time.  By the time the sun heats up the pile to where it can start to dry (if there is sun) then it sets for the night!  #%$&* winter!

I have been asked, "Can I add an external heat source to my solar kiln?" Well, maybe, I guess.  Sounds kinda dangerous to me though, dry wood, a heat source, a fan to fuel the flames, a remote to semi remote kiln location.  I wouldn't do it, and I bet your neighbor that you took the cherry tree wouldn't appreciate it either. It would add insult to injury if you set his house on fire drying the lumber from the tree you stole out of his yard!

Thanks for reading,

Kevin Koski

Dry Kiln

Owner and Operator

CurlyMapleWood.com

www.curlymaplewood.com

Just uploaded some outstanding RED Pennsylvanian cherry sets!