Cherry Drying

[cody michael]

Hello,

I just recently bought a sawmill and cut up some cherry logs, I want to use a few pieces to make shelves in my kitchen some 1-1.5in for wall shelves and a thicker 2in piece for a counter height shelf/ledge (no cabinet underneath).

I had planned on taking these out to get kiln dried but every place around is either crazy ($2 a bdft for the thicker stuff) or won't run small batches. These logs have been down for a while (don't know exact age but ends were dark and weathered, I am guessing over a year) before I cut them up, they have been air drying for a few weeks now. I live in Michigan and it is getting cold out, any idea how long I would need to wait before I use them? With my usage just being a board mounted on the wall can I use it with a little higher moisture then you would want for furniture?

I have a small de-humidification kiln I built I have used as a sterilization chamber, would it be worth putting it in there? I try not to use that during the winter due to energy cost the walls are 4in styrofoam but it still seems a lot harder to heat when its cold out. Any idea how much being in a home built kiln like this will speed things up?

Or do I just need to be patient and wait for it to air dry?

[John TenEyck]

For many woods, air drying takes at least 4 months for 4/4, and easily double that if cut in the Fall. 8/4 takes 12 - 18 months, or more. The logs being down for a year probably won't shorten that too much. if you want to use those boards this winter you'll have to dry them, and your dehumidification kiln should be just the ticket if you know how to run it. You can look up drying schedules for kilns on the Forest Products Laboratory website, or on EBAC's website, maker's of dehumidification kilns so a good source. Virginia Tech's info on solar driers shows cherry can have a maximum daily moisture loss of 5.8% for 4/4 and 2.3% for 8/4. So, those rates will tell you the minimum drying time, based on the actual moisture content your lumber now has.

John

[cody michael]

For many woods, air drying takes at least 4 months for 4/4, and easily double that if cut in the Fall. 8/4 takes 12 - 18 months, or more. The logs being down for a year probably won't shorten that too much. if you want to use those boards this winter you'll have to dry them, and your dehumidification kiln should be just the ticket if you know how to run it. You can look up drying schedules for kilns on the Forest Products Laboratory website, or on EBAC's website, maker's of dehumidification kilns so a good source. Virginia Tech's info on solar driers shows cherry can have a maximum daily moisture loss of 5.8% for 4/4 and 2.3% for 8/4. So, those rates will tell you the minimum drying time, based on the actual moisture content your lumber now has.

John

I don't know how to run but I guess now may be the time to learn lol. Thank you.

[John TenEyck]

I don't know how to run but I guess now may be the time to learn lol. Thank you.

Good idea. You know, you have to follow a schedule for sterilizing wood, too, if you want to avoid problems. Heat up no faster than 25 deg F/day. Cool down no more than 40 deg F/day.

John

[cody michael]

I did not know that, thanks, I have increased temp around that speed normally just so it is easier on heater but normally I just turned off heat, with how well insulated it is it probably drops around 40 a day but next time I will pay more attention.

[cody michael]

I just have a household dehumidifier my plan is to let it run and every so often lower the humidity, I know there are charts but I don't understand them, any suggestions on how often I should lower the humidity setting on the dehumidifier and how much I should lower it each time? I assume I should keep the fan on all the time? Should I have the heater on during this time or only at the end to sterilize? is starting at a higher humidity and lowering like 5-10% each week workable?

[John TenEyck]

I just have a household dehumidifier my plan is to let it run and every so often lower the humidity, I know there are charts but I don't understand them, any suggestions on how often I should lower the humidity setting on the dehumidifier and how much I should lower it each time? I assume I should keep the fan on all the time? Should I have the heater on during this time or only at the end to sterilize? is starting at a higher humidity and lowering like 5-10% each week workable?

In my prior post I noted that the maximum daily drying rate for 4/4 cherry is 5.8% and for 8/4 it's 2.3%. It doesn't matter much how you do it. So, put the wood in a plastic tent so the RH is constant for all the wood. Do not do this w/o the tent because the boards on the outside of the stack will dry much faster than those in the center. OK, put the dehumidifier, a small oil filled heater, and a fan inside the tent. The fan will circulate the air so all the boards see uniform RH. The heater drives the moisture out of the lumber, and the dehumidifier gets rid of it.

OK, to run it you need to cut at least one specimen cut from the middle of one of the boards that you weigh daily. Yes, daily. Make it about 24" long. Now cut off a piece about 2 or 3 " long and weigh both pieces immediately. Write the respective weight on each piece. Put the small piece in a toaster oven at 220F until the weight is constant for several hours. The moisture content of your lumber is:

(Wet weight - dry weight) / dry weight x 100 = % moisture content.

You can throw the little piece away now. Put the larger piece in the outside row of your lumber stack at mid height, with the other pieces from that board on each side. Use thinner stickers under the specimen so you can remove it for daily weighing. Button up the enclosure and turn on the dehumidifier, heater and fan. Start with the dehumidifier at 90% RH, and the heater at 90F and the fan on.

Let's say the MC was 60%. OK, if it's 4/4 stock, you can dry it at a rate of 5.8% per day. That means the MC needs to be no lower than 60 - 5.8 = 54.2% after one day of drying. The following day it can be no lower than 54.2 - 5.8 = 48.4%. And so on. To determine the daily % MC, weigh the specimen, take it out of the enclosure and weigh it. The MC that day is:

Calculated final dry weight = Original Wet Weight - (Original Wet Weight x % MC/100). So for a specimen that weights 2000 gms with 60% MC the calculated final dry weight is = 2000 - (2000 x 60/100) = 800 gms.

Now calculate the daily %MC from: (Daily weight - Dry Weight) / Dry weight x 100 = Daily %MC

It's not as hard as it looks. But if you don't want to do that, then get a moisture meter that can read both 1/4" and 3/4" deep, and measure the % moisture at both depths each day. Take several readings at the 1/4" depth with 4/4 stock and at both depths for 8/4 stock. The average of your readings is a reasonable estimate of the moisture content, though not as accurate as the calculated method.

As the daily %MC goes down it will stall at each condition you set for the dehumidifier and heater. Lower the dehumidifier in 5% increments until no water is removed, then increase the temperature to 100F. Some more water should be removed by the next day but if not, lower the RH by 5%. Keep increasing temp and lowering the % RH, but do not go higher than 120 - 130F, or lower than about 20% RH. Do not exceed the maximum daily % moisture loss. At some point the daily % moisture content will get down to 6 - 8%, which for your 2000 gm specimen means it will weigh 800 x 1.06 to 1.08 = 848 to 864 gms. At that point lower the temp., but no more than 40F per day, until cool. You're done.

If all that sounds too hard, then let it air dry until it's down to the equilibrium moisture level of your area (12 - 14% where I live) and then bring it indoors, sticker it, and let it dry until it's 6 - 8% or whatever moisture content you want.

John

[cody michael]

In my prior post I noted that the maximum daily drying rate for 4/4 cherry is 5.8% and for 8/4 it's 2.3%. It doesn't matter much how you do it. So, put the wood in a plastic tent so the RH is constant for all the wood. Do not do this w/o the tent because the boards on the outside of the stack will dry much faster than those in the center. OK, put the dehumidifier, a small oil filled heater, and a fan inside the tent. The fan will circulate the air so all the boards see uniform RH. The heater drives the moisture out of the lumber, and the dehumidifier gets rid of it.

OK, to run it you need to cut at least one specimen cut from the middle of one of the boards that you weigh daily. Yes, daily. Make it about 24" long. Now cut off a piece about 2 or 3 " long and weigh both pieces immediately. Write the respective weight on each piece. Put the small piece in a toaster oven at 220F until the weight is constant for several hours. The moisture content of your lumber is:

(Wet weight - dry weight) / dry weight x 100 = % moisture content.

You can throw the little piece away now. Put the larger piece in the outside row of your lumber stack at mid height, with the other pieces from that board on each side. Use thinner stickers under the specimen so you can remove it for daily weighing. Button up the enclosure and turn on the dehumidifier, heater and fan. Start with the dehumidifier at 90% RH, and the heater at 90F and the fan on.

Let's say the MC was 60%. OK, if it's 4/4 stock, you can dry it at a rate of 5.8% per day. That means the MC needs to be no lower than 60 - 5.8 = 54.2% after one day of drying. The following day it can be no lower than 54.2 - 5.8 = 48.4%. And so on. To determine the daily % MC, weigh the specimen, take it out of the enclosure and weigh it. The MC that day is:

Calculated final dry weight = Original Wet Weight - (Original Wet Weight x % MC/100). So for a specimen that weights 2000 gms with 60% MC the calculated final dry weight is = 2000 - (2000 x 60/100) = 800 gms.

Now calculate the daily %MC from: (Daily weight - Dry Weight) / Dry weight x 100 = Daily %MC

It's not as hard as it looks. But if you don't want to do that, then get a moisture meter that can read both 1/4" and 3/4" deep, and measure the % moisture at both depths each day. Take several readings at the 1/4" depth with 4/4 stock and at both depths for 8/4 stock. The average of your readings is a reasonable estimate of the moisture content, though not as accurate as the calculated method.

As the daily %MC goes down it will stall at each condition you set for the dehumidifier and heater. Lower the dehumidifier in 5% increments until no water is removed, then increase the temperature to 100F. Some more water should be removed by the next day but if not, lower the RH by 5%. Keep increasing temp and lowering the % RH, but do not go higher than 120 - 130F, or lower than about 20% RH. Do not exceed the maximum daily % moisture loss. At some point the daily % moisture content will get down to 6 - 8%, which for your 2000 gm specimen means it will weigh 800 x 1.06 to 1.08 = 848 to 864 gms. At that point lower the temp., but no more than 40F per day, until cool. You're done.

If all that sounds too hard, then let it air dry until it's down to the equilibrium moisture level of your area (12 - 14% where I live) and then bring it indoors, sticker it, and let it dry until it's 6 - 8% or whatever moisture content you want.

John

Thanks that is a very informative write up, I did not realize how complicated it was. These trees have been done for at least a year and air drying for about a month. When I checked there moisture with my meter (pin style) it's around 18-20%. If I want to get to around 8% it should only take a few weeks right? Even if I tried to target 1% a day 10-12 days would do it if I understand what your saying.

I will need to do some thinking, my current setup is very hard to open accept a small opening at the end where dehumidifier goes.

[Bill Bukovec]

I've heard that one drawback of pin style moisture meters is it only measures the moisture on the outer surface of the board. The moisture content on the inside may be higher.

[Mel Fulks]

1 and 1/2 inch….,why so thick? That’s for log cabins. A shelf gets air on both sides , it will dry . If there is a slight cup in a board ….
then use “that side up “ , it will give safer space to the salt , pepper …. and Knick Knacks . The “price-less” stuff in the museum houses
was all air dried, give nature and ….modern heating a chance!