Solar kiln for hardwoods part deux

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jaoneill

Feeling the Heat
Do you know your plastic costs for those 22 pallets? That is 11 cords, a lot! I am curious how you do your wrapping. Is your wood stacked flat on top or rounded top? You put the 4mil poly on the top? How? You just wrap round and round the bottom with the shrink wrap? Wrap just one layer thick? Is all of this enclosed or is there any venting?
Single layer of 4 mil over rounded top, corners tacked with stapler to hold in place while I wrapped the sides. Shrink wrap overlapped about by half, so effectively double. One 10x50 roll and a little bit of poly; roll was about $40, one 18"X1000' roll of shrink-wrap and a little bit. I think the 4 roll case of shrink wrap was about $50, and the dispenser $25 +/-. One pic shows the first few individually wrapped this, second one the start of last year's 2-4 pallets in one kilns

IMG_1033.jpg IMG_0910.JPG
 

jaoneill

Feeling the Heat
An interesting update: we brought another three skids into the woodshed the other day, one of which turned out to be somewhat problematic. This one contains primarily smooth bark hickory, especially near the top of the stacks. I thought the splits seemed a bit heavy but hickory is heavy relative to sugar maple or beech so it didn't concern me, then I found the boiler struggling to keep up with the demand for heat. Still didn't quite connect the dots until I threw in some maple this morning and the boiler immediately shot up to the shutdown point, then maintained temp with the outside temp at -10f.
So, this particular hickory tree, for whatever reason, even with its splits being at or near the top of the stack in the "kiln", only dried down to 18%-20%, as opposed to the maple at the bottom of the same skid that is at 10%-12%; go figure. In the two years that I have used this process I have never seen this type of discrepancy.
 

Woodsplitter67

Minister of Fire
Jan 19, 2017
2,455
Woolwich nj
I am really interested in your simple setup for red oak. Do you think if I set this up in the spring I can get the red oak to less than 20% by fall?

Yes.. I think you'll be ok.. You will need to split your wood soon and stack it and top cover untill early june.. zip check the kiln at the end of August and see where your at.. you may need to go into September..
 
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jaoneill

Feeling the Heat
I am really interested in your simple setup for red oak. Do you think if I set this up in the spring I can get the red oak to less than 20% by fall?
I agree with woodsplitter's comment that you should be ok. This is my second year with the kiln project and as I said above, the first time this has happened that I am aware of. This is an ongoing learning process and slightly different for each of us as location, wood, and appliance type are all contributing factors to the experience. I have learned that my gasification boiler does best with maple or beech. Due to how they burn and coal up the fire will keep the "nozzles" nicely covered with coals, maximizing the combustion of all of the gases. Hickory and elm will be reduced to ashes without falling down the sloping floor of the upper chamber to cover the nozzles, often forming a hard "crust" that will prevent splits from "falling" into the burn zone and often block the nozzles completely. This is all magnified if the splits are over 15% and gets worse as moisture level goes up. My ideal burn seems to be achieved with, in order of efficiency, sugar maple, beech, and cherry (all of which I have virtually an endless supply of) under 15% moisture. Not to say that I don't or won't burn other species, but these three are definitely the easiest to burn and hold a good fire with.
 

MR. GLO

Feeling the Heat
Jan 26, 2021
355
Massachusetts
Im thinking its going to be about 14 to 18%.
I did a kiln 2 years ago and left it in there to long.. i started in at this time and opened the kiln in october my oak was like 8% and the cherry was at 2%.... wayyyyyy to dry.. 60 days will be plenty...
Nice setup. The problem with buying kiln dry wood in my area is the larger logs when split and tested have a much different reading and failed at 26 percent. Did you have any large logs over 18 percent?
 

Woodsplitter67

Minister of Fire
Jan 19, 2017
2,455
Woolwich nj
Nice setup. The problem with buying kiln dry wood in my area is the larger logs when split and tested have a much different reading and failed at 26 percent. Did you have any large logs over 18 percent?

I am not drying logs. I dry my splits that go into my stove. The larger being 5x5 inches to the smaller stuff 1.5x1.5 all lengths to 18 inches. All of my stuff was 18%MC or less
 
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MoDoug

Minister of Fire
Feb 3, 2018
583
NE Missouri
This will be my kiln, it's exactly like my other wood stacks, except it's oriented N/S and in a location that will receive full sun from about noon till sundown. I did build a taller 2x4 into the ends and allowed space in the middle for more, these will support my horizontal boards that my clear plastic will drape over. It's 24' long, and will hold about 2.4 cords. It's almost all red oak on the visible side, with white oak, maple, ash, black oak and hickory on the other.
1615523274512.jpeg
 
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Woodsplitter67

Minister of Fire
Jan 19, 2017
2,455
Woolwich nj
This will be my kiln, it's exactly like my other wood stacks, except it's oriented N/S and in a location that will receive full sun from about noon till sundown. I did build a taller 2x4 into the ends and allowed space in the middle for more, these will support my horizontal boards that my clear plastic will drape over. It's 24' long, and will hold about 2.4 cords. It's almost all red oak on the visible side, with white oak, maple, ash, black oak and hickory on the other.
View attachment 276244

that looks good.. just as a heads up.. you can go 3 or 4 splits wide if you want.. when are u going to wrap it.. your going to top cover this untill your ready to wrap.. correct
 

Rob_Red

Feeling the Heat
Feb 2, 2021
376
Southern New England
This will be my kiln, it's exactly like my other wood stacks, except it's oriented N/S and in a location that will receive full sun from about noon till sundown. I did build a taller 2x4 into the ends and allowed space in the middle for more, these will support my horizontal boards that my clear plastic will drape over. It's 24' long, and will hold about 2.4 cords. It's almost all red oak on the visible side, with white oak, maple, ash, black oak and hickory on the other.
View attachment 276244
looks great I'm going to start on mine this weekend. Do you plan to burn that wood this coming season?
 

MoDoug

Minister of Fire
Feb 3, 2018
583
NE Missouri
@Woodsplitter67 Good to know about going 3 or 4 splits wide, the plan is for this to get me through next season, after that I'll be good to go for about 5 years without kilning. My plan on this went slightly awry when I didn't collect as much dead wood as planned, the dead red oak is anywhere from 23 - 28% MC. So I ended up loading the back side with all green wood. I'm sure the seasoning times will vary. I wish the green wood was on the west side, but it isn't. If the red oak reaches 18+- MC, I may unwrap it, and rewrap just the green wood. I plan on wrapping it about June 1st, I'll check the MC and monitor it during the summer. It'll work out.

And yes, I will top cover soon, maybe even today.

@Rob_Red , yes, this will be for next season. Let us know how it goes for you.
 

MoDoug

Minister of Fire
Feb 3, 2018
583
NE Missouri
I got the top cover done. I had some leftover 6 mil plastic sheeting from a vapor barrier job, it's not what I want long term, but it will work for now. It's coming off in June anyway.

1615613149215.jpeg
 

JohnWW

Member
Jul 8, 2019
61
63119
Experimental kiln. Pallet slats on all corners to make a void to build up heat. From the pic it looks like there are gaps but the pallet wrap is continuous apart from a gap at the bottom. Interestingly the wrap withstood substantial and sustained winds for a couple of days and it was the tar paper roof that got trashed by the wind. The wrap flexed like a spiderweb and accidentally I have wind activated venting. Will rebuild with better roof substrate. Wrap is HD 15”.
 

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Woodsplitter67

Minister of Fire
Jan 19, 2017
2,455
Woolwich nj
Experimental kiln. Pallet slats on all corners to make a void to build up heat. From the pic it looks like there are gaps but the pallet wrap is continuous apart from a gap at the bottom. Interestingly the wrap withstood substantial and sustained winds for a couple of days and it was the tar paper roof that got trashed by the wind. The wrap flexed like a spiderweb and accidentally I have wind activated venting. Will rebuild with better roof substrate. Wrap is HD 15”.

keep the top clear and.make sure you vent it right away. it's a little early to start the kiln.. how long ago was it split
 
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JohnWW

Member
Jul 8, 2019
61
63119
keep the top clear and.make sure you vent it right away. it's a little early to start the kiln.. how long ago was it split
Thanks. Split last week but 5 ft logs stored of ground for 2 summers. Half rounds and rounds mostly. Mostly wanting to see how the thin wrap would hold up. I have other stacks of splits that I will wrap too when I have my technique down.
 

Woodsplitter67

Minister of Fire
Jan 19, 2017
2,455
Woolwich nj
Thanks. Split last week but 5 ft logs stored of ground for 2 summers. Half rounds and rounds mostly. Mostly wanting to see how the thin wrap would hold up. I have other stacks of splits that I will wrap too when I have my technique down.

I'd wait on wrapping the wood untill early June. That wood is wet and needs to dry some prior to you starting the kiln.. if you wrap I now you'll have trouble drying it out..you'll know it's ready when the stack starts to shift
 
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neverbilly

Burning Hunk
Dec 27, 2015
177
Arkansas, USA
I have a 2-cord stack of red oak on six pallets. The stack has a bit of a crown to it so the axis of the stack is higher than the sides to give kind of a ridge line to it. I wrapped with the saran-wrap stuff starting at the bottom and going to top of stack. I then applied a top of a 10' x 25' 3-mil plastic sheeting. I already had the 3-mil, so, I used it because the 6-mil is $40/roll for the 10' x 25' and I thought that was too high. Unless the 6-mil will last multi-seasons.

Question... since I have been reading on this forum about doing the solar kiln, I don't ever remember anyone talking about 'weep holes' at the bottom of the stack. Meaning weep holes in a plastic sheeting that was laid down on the pallets before stacking the wood. To allow moisture to condense and then fall through the weep holes. Anyway, I recently came across info on another forum and it was claimed that weep holes in bottom plastic sheeting works. My question is... if weep holes in plastic work, why couldn't you just do as I did, stack the wood on the pallets, wrap as I did and that's it. No vent slits needed, the 'weep holes' would be the openings in the slats of the pallets.

In lieu of that... if I were to cut vent slits in my 2-cord solar kiln, put them where? I assume it is near the apex at each end on the 'ridge line?' I think I recall someone said cut a u-shape slit? Is this about a hand-width size flap, one at each end?

Question... I only wrapped one layer of the saran-wrap stuff on the sides. Do you need more than one layer of wrap?

This heat wave is going to be cooking bigtime and we haven't even gotten to the first day of summer! It will be 100 degrees and more here.

I forgot to take pics.
 

johneh

Minister of Fire
Dec 19, 2009
4,361
Eastern Ontario
Question... since I have been reading on this forum about doing the solar kiln, I don't ever remember anyone talking about 'weep holes' at the bottom of the stack. Meaning weep holes in a plastic sheeting that was laid down on the pallets before stacking the wood.
Did you put plastic on the pallets?
Then wrapped the stacks and sealed the top?
No airflow you now have a prime zone to rot the wood
For a solar kiln to work it must be vented to allow humid
air to escape. The idea is to heat the air in the kiln to draw off moisture
at a faster rate than daytime temperature. That hot humid has to escape somehow.
The bottom should be open so air can freely enter the kiln to replace
the hot moisture-laden air
 
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Woodsplitter67

Minister of Fire
Jan 19, 2017
2,455
Woolwich nj
I have a 2-cord stack of red oak on six pallets. The stack has a bit of a crown to it so the axis of the stack is higher than the sides to give kind of a ridge line to it. I wrapped with the saran-wrap stuff starting at the bottom and going to top of stack. I then applied a top of a 10' x 25' 3-mil plastic sheeting. I already had the 3-mil, so, I used it because the 6-mil is $40/roll for the 10' x 25' and I thought that was too high. Unless the 6-mil will last multi-seasons.

Question... since I have been reading on this forum about doing the solar kiln, I don't ever remember anyone talking about 'weep holes' at the bottom of the stack. Meaning weep holes in a plastic sheeting that was laid down on the pallets before stacking the wood. To allow moisture to condense and then fall through the weep holes. Anyway, I recently came across info on another forum and it was claimed that weep holes in bottom plastic sheeting works. My question is... if weep holes in plastic work, why couldn't you just do as I did, stack the wood on the pallets, wrap as I did and that's it. No vent slits needed, the 'weep holes' would be the openings in the slats of the pallets.

In lieu of that... if I were to cut vent slits in my 2-cord solar kiln, put them where? I assume it is near the apex at each end on the 'ridge line?' I think I recall someone said cut a u-shape slit? Is this about a hand-width size flap, one at each end?

Question... I only wrapped one layer of the saran-wrap stuff on the sides. Do you need more than one layer of wrap?

This heat wave is going to be cooking bigtime and we haven't even gotten to the first day of summer! It will be 100 degrees and more here.

I forgot to take pics.
there is no plastick under the wood.. only around it. the plastic is only to wrap the outside and is to go below the bottom row of wood to keep it dry. The air is supposed to come up from underneath the kiln and go out the top vents.. you need to cut the plastic that is underneath the stacked wood or its probably not going to work
 

neverbilly

Burning Hunk
Dec 27, 2015
177
Arkansas, USA
I do not have plastic laid atop the pallets. I didn't say that. My stack is right atop the pallets. I said that I have read elsewhere that OTHER people have laid plastic down atop their pallets and they then cut 'weep holes' into that plastic. So that the kiln can 'weep' the condensation. As opposed to reading on here that you MUST have vents to allow the moisture to escape. If you guys have never heard of 'weep holes' rather than venting, I guess you can ignore that unless you know what I am talking about that the other people have reported.

Regarding the other guys laying down plastic and cutting weep holes, I also said I don't understand why you couldn't just allow the moisture to 'weep' into the slots between the boards on the pallets... instead of escaping through weep holes cut into plastic that was laid down (in their kilns).

In that other thread on another forum, lots of people told the guy his weep holes cut into plastic would NOT work, that he MUST have vents. And he proved them wrong, proving that moisture escaped into his weep holes.

Anyway, I planned on doing the vents all along, I just need to know where and how big. And I also asked if one layer of the saran-wrap stuff is sufficient.

Thanks for answers to these questions!
 
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jaoneill

Feeling the Heat
I do not have plastic laid atop the pallets. I didn't say that. My stack is right atop the pallets. I said that I have read elsewhere that OTHER people have laid plastic down atop their pallets and they then cut 'weep holes' into that plastic. So that the kiln can 'weep' the condensation. As opposed to reading on here that you MUST have vents to allow the moisture to escape. If you guys have never heard of 'weep holes' rather than venting, I guess you can ignore that unless you know what I am talking about that the other people have reported.

Regarding the other guys laying down plastic and cutting weep holes, I also said I don't understand why you couldn't just allow the moisture to 'weep' into the slots between the boards on the pallets... instead of escaping through weep holes cut into plastic that was laid down (in their kilns).

In that other thread on another forum, lots of people told the guy his weep holes cut into plastic would NOT work, that he MUST have vents. And he proved them wrong, proving that moisture escaped into his weep holes.

Anyway, I planned on doing the vents all along, I just need to know where and how big. And I also asked if one layer of the saran-wrap stuff is sufficient.

Thanks for answers to these questions!
I could be off base but my take is that there was miscommunication about the plastic under the kiln somewhere along the line. The dude that cut the weeps in the bottom plastic most likely had that plastic under his pallets to minimize moisture migrating up from the damp ground, in which case it almost makes sense. To solve the ground moisture issue, I put a sacrificial, junk pallet on the ground with a good pallet on top of it. This gets the wood 8+ inches off the ground which also facilitates air flow and loaded pallet retrieval when everything freezes to the ground (as it does here by mid-December). The first year that I stacked on pallets 90% of them were destroyed when I tried to free them from the frozen ground.
Vents should be at the highest points in the stack. Start with them relatively small 4"x5" or so. If after 2 or 3 days you continue to see moisture collecting on the inside of the plastic, make them larger.
 

Foxhole Farm

New Member
Jul 11, 2022
1
05301
First I just want to say thanks to ya'll for all of your posts on the mini kiln. I'm trying to do the same and I have a few questions I am wondering if you could help me out with.

Being my first year with a gasser I didn't have a few seasons to prep this winters wood. I bought log length which I am processing for the next two winters, but for this winter I bought split/seasoned, which we all know means.... it aint gonna be dry enough lol.

After a sleepless night researching ways to dry my wood faster, I came across you posts on making mini kilns.

I'm going to try the same. My plan: I'm going to split all my incoming "seasoned" wood down to 3-4" diameter this coming weekend. Stack in IBC totes. Wrap them in 18" stretch plastic along the sides leaving the bottom open. Use 6mil poly as a cover and use some conduit, fasten it to the IBC totes to make a small hoop structure, to give some extra clearance on the top. I'll cut the vents on the verticle ends of the hoops so water will have a tough time getting through. I'll store them up on a second pallet, out in the sun until early November then stick them in the barn.

So, I shared my plan with some wood gasser folks and here is what they said:

"All that's going to do is make it moldy and rotten. Unwrap it for faster drying"

"He must be testing his moisture on the side of the wood, tell him he has to split it again and test the middle"

"Where is the 5 Gallons of moisture going to go?"

"Its not going to work, you need ventilation"

I'm getting the impression alot of folks don't think it will work, or make it worse, and I am alittle concerned they are right, so I thought I would reach out.

So a few questions for you:

1. Does my plan sound like it will work?

2. You are splitting your test piece first, then testing in the middle right?

Lol, I'm just looking for a little reassurance that I am not being foolish by giving it a go with 7 cord in July.

Thanks, I appreciate it in advance
 
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jaoneill

Feeling the Heat
First I just want to say thanks to ya'll for all of your posts on the mini kiln. I'm trying to do the same and I have a few questions I am wondering if you could help me out with.

Being my first year with a gasser I didn't have a few seasons to prep this winters wood. I bought log length which I am processing for the next two winters, but for this winter I bought split/seasoned, which we all know means.... it aint gonna be dry enough lol.

After a sleepless night researching ways to dry my wood faster, I came across you posts on making mini kilns.

I'm going to try the same. My plan: I'm going to split all my incoming "seasoned" wood down to 3-4" diameter this coming weekend. Stack in IBC totes. Wrap them in 18" stretch plastic along the sides leaving the bottom open. Use 6mil poly as a cover and use some conduit, fasten it to the IBC totes to make a small hoop structure, to give some extra clearance on the top. I'll cut the vents on the verticle ends of the hoops so water will have a tough time getting through. I'll store them up on a second pallet, out in the sun until early November then stick them in the barn.

So, I shared my plan with some wood gasser folks and here is what they said:

"All that's going to do is make it moldy and rotten. Unwrap it for faster drying"

"He must be testing his moisture on the side of the wood, tell him he has to split it again and test the middle"

"Where is the 5 Gallons of moisture going to go?"

"Its not going to work, you need ventilation"

I'm getting the impression alot of folks don't think it will work, or make it worse, and I am alittle concerned they are right, so I thought I would reach out.

So a few questions for you:

1. Does my plan sound like it will work?

2. You are splitting your test piece first, then testing in the middle right?

Lol, I'm just looking for a little reassurance that I am not being foolish by giving it a go with 7 cord in July.

Thanks, I appreciate it in advance
Always keep in mind that the keys to this process are enough ventilation and plenty of sunlight. Last year I was tied up with other things and finally in late June hired some help to stack my pallets without a thought to tell the help not to stack them too close together. I ended up with three rows only a few feet apart and as a result the lower half of the splits in each of the pallets in the center row only dried down to 23%-26%. The row to the east was somewhat better but only the row to the west, where the sun could bake it through the heat of the day, gave me the results that I typically get. (they also did a lousy job of stacking)

The one pic is a lesson in what not to do, second gives a visual of the results; top of stack noticeably drier than the lower part.

IMG_1282.jpg IMG_1221.jpg
 

Woodsplitter67

Minister of Fire
Jan 19, 2017
2,455
Woolwich nj
First I just want to say thanks to ya'll for all of your posts on the mini kiln. I'm trying to do the same and I have a few questions I am wondering if you could help me out with.

Being my first year with a gasser I didn't have a few seasons to prep this winters wood. I bought log length which I am processing for the next two winters, but for this winter I bought split/seasoned, which we all know means.... it aint gonna be dry enough lol.

After a sleepless night researching ways to dry my wood faster, I came across you posts on making mini kilns.

I'm going to try the same. My plan: I'm going to split all my incoming "seasoned" wood down to 3-4" diameter this coming weekend. Stack in IBC totes. Wrap them in 18" stretch plastic along the sides leaving the bottom open. Use 6mil poly as a cover and use some conduit, fasten it to the IBC totes to make a small hoop structure, to give some extra clearance on the top. I'll cut the vents on the verticle ends of the hoops so water will have a tough time getting through. I'll store them up on a second pallet, out in the sun until early November then stick them in the barn.

So, I shared my plan with some wood gasser folks and here is what they said:

"All that's going to do is make it moldy and rotten. Unwrap it for faster drying"

"He must be testing his moisture on the side of the wood, tell him he has to split it again and test the middle"

"Where is the 5 Gallons of moisture going to go?"

"Its not going to work, you need ventilation"

I'm getting the impression alot of folks don't think it will work, or make it worse, and I am alittle concerned they are right, so I thought I would reach out.

So a few questions for you:

1. Does my plan sound like it will work?

2. You are splitting your test piece first, then testing in the middle right?

Lol, I'm just looking for a little reassurance that I am not being foolish by giving it a go with 7 cord in July.

Thanks, I appreciate it in advance

please read post number 1 it Describes how to putthe kiln together, it also says u shaped vents.. the vents are for the warm moistur laden air to excape and the fresh air come up from the bottom. You may see moisture the first few days.. after that you should be good as long as your venting enouth air. you need to check the temp of the kiln.. you want it like 140 degrees in there..

if you put it together correctly you will have no issues..
 
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Poindexter

Minister of Fire
Jun 28, 2014
2,814
Fairbanks, Alaska
weep holes.
Sorry for the delay. I have failed at growing heirloom tomato this summer and suddenly have some free time.

On the one hand I absolutely defer to @Woodsplitter67 for kilning east coast hardwoods, on the other, there is a ton of variation here within single zip codes.

I am about a mile from the nearest river on alluvial silt (flood plain) with my water table at about 20 feet. 2 miles away, in the same zip, is a co worker of mine up on a ridge that had to drill through 150 feet of gravel to find dirt to drill when he was putting in a well. I have a lot more ground water to deal with than he ever sees. My coworker has fabulous drainage, I don't.

When I built my kilns I put cinderblocks on subsoil after removing the topsoil, then ground contact rated pressure treated floor framing, then a thick layer of plastic moisture barrier, then not PT plywood for the kiln floors. For air inlet at the bottom I have a nominal 3/4 inch gap between the flooring and the membrane all around, and good results, in an area with a lot of ground water. Mine are 40 inches wide, 2 splits with an air gap in the middle.

IIRC woodsplitter's first kiln was a single split width, and open at the bottom. I have no idea how deep his water table is or how good his drainage is.

My biggest kiln holds 2.75 cords. With sealed floors, 3/4 inch airgap x 44 running feet and top vent sized roughly one cantaloupe per cord, standing green spruce in January that I split and stack in March is ready to burn July fourth.

I can't possibly know the conditions on your lot without several site visits. If you are willing to bring in a keg of Guinness and pay my airfare x 4 I will come take 4 looks and sleep in the garage next to the keg. Otherwise build with a sealed floor and let the chipmunks work on it. When your wood gets to be marginal for burning you got too many weep holes in your floor's vapor barrier.
 
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