# Vacuum kiln



## Mike1950 (Mar 10, 2020)

@rob3232 posted this link elsewhere and I think it should be here- long read but informative.
https://link.springer.com/article/10.1007/s40725-016-0045-9

Reactions: Like 1 | Agree 1 | Informative 2


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## TXMoon (Mar 10, 2020)

I've wondered about this. Reading it now.

Reactions: Like 1


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## TXMoon (Mar 10, 2020)

Interesting read though a lot of it was a bit too technical and seemed to me to be geared more toward construction lumber. But from what I understand of the article they are recommending using vacuum with a heat source. How about us hobbyist? I have a X x Y x 3" blank that will fit in my vacuum pot. Can I use that along or do I need to set it on a low temp hot plate too? I was thinking of sitting the wood on an inch or so of desiccant type cat little and just putting it under a vacuum until I see moisture bubble up from the wood. 

Your thoughts?

Reactions: Like 1


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## Mike1950 (Mar 10, 2020)

My friend dries coco and honduran in his. says there is a learning curve but results are much less degrade.. with very quick turnaround...

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## Mike1950 (Mar 10, 2020)

TXMoon said:


> Interesting read though a lot of it was a bit too technical and seemed to me to be geared more toward construction lumber. But from what I understand of the article they are recommending using vacuum with a heat source. How about us hobbyist? I have a X x Y x 3" blank that will fit in my vacuum pot. Can I use that along or do I need to set it on a low temp hot plate too? I was thinking of sitting the wood on an inch or so of desiccant type cat little and just putting it under a vacuum until I see moisture bubble up from the wood.
> 
> Your thoughts?


I have wondered the same. but I think there would have to be a water trap to keep water out of pump.
I doubt you would need a heat source- they tell me it is warm in Texas....


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## TXMoon (Mar 10, 2020)

Mike1950 said:


> I have wondered the same. but I think there would have to be a water trap to keep water out of pump.
> I doubt you would need a heat source- they tell me it is warm in Texas....


I was hoping the desiccant would help keep water out of the pump but some sort of trap couldn't hurt. For sure this summer I wouldn't need one but it's still only in the 50s to 70s here.

Reactions: Like 1


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## Mike1950 (Mar 10, 2020)

TXMoon said:


> I was hoping the desiccant would help keep water out of the pump but some sort of trap couldn't hurt. For sure this summer I wouldn't need one but it's still only in the 50s to 70s here.


I am always amazed at how much water is in wood. I put a batch of burl in kiln about 5 weeks ago. started out at a drip a second= 5 gallons a day- just got below 1 drip every 5 seconds - which is 3 quarts a day- lot of water out of 22% burl


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## TXMoon (Mar 10, 2020)

Mike1950 said:


> I am always amazed at how much water is in wood. I put a batch of burl in kiln about 5 weeks ago. started out at a drip a second= 5 gallons a day- just got below 1 drip every 5 seconds - which is 3 quarts a day- lot of water out of 22% burl


Yikes! Then a trap with a drain is going to be needed. Hold my beer....

Reactions: Like 1


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## Mike1950 (Mar 10, 2020)

TXMoon said:


> Yikes! Then a trap with a drain is going to be needed. Hold my beer....


kiln is a 5'x6'x12' box


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## TXMoon (Mar 10, 2020)

Mike1950 said:


> kiln is a 5'x6'x12' box


Mine is a 5 gallon SS vacuum pot. A bowl blank should fit in there.


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## Mike1950 (Mar 10, 2020)

TXMoon said:


> Mine is a 5 gallon SS vacuum pot. A bowl blank should fit in there.



I think dry BLM weighs 3lb a bd ft wet 4. so 12x12 x5 would lose 5lbs. I think water weighs about 8 lbs a gallon. little over 2 quarts- seems like an awful lot of water but i think numbers are right


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## TXMoon (Mar 10, 2020)

Mike1950 said:


> I think dry BLM weighs 3lb a bd ft wet 4. so 12x12 x5 would lose 5lbs. I think water weighs about 8 lbs a gallon. little over 2 quarts- seems like an awful lot of water but i think numbers are right


Sounds right. Is that taking it down to 0% moisture? It'll be an interesting experiment if nothing else.

Reactions: Like 1 | Useful 1


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## Mike1950 (Mar 10, 2020)

TXMoon said:


> Sounds right. Is that taking it down to 0% moisture? It'll be an interesting experiment if nothing else.


my guess is those rough numbers 4lbs and 3 are green vs 6%


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## Mike1950 (Mar 10, 2020)

TXMoon said:


> Sounds right. Is that taking it down to 0% moisture? It'll be an interesting experiment if nothing else.


the industry does not req. 0%

Reactions: Like 1


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## trc65 (Mar 10, 2020)

Some random thoughts from someone who knows only what he has read in the last couple of days, i.e. next to nothing...

You will definitely need a condenser/trap on the vacuum line. 

The "evaporation" of water from the wood has a net cooling effect on the wood and without some sort of heating element, results in the need to run "cycles" so that the wood can warm up between vacuum cycles and be able to continue to release moisture. 

A lot of people in different discussion forums have said it just isn't worth the trouble to try it for the average hobbyist. Unless, you are dealing with some expensive, hard to dry woods that degrade with conventional drying methods.

Most discussions have ended with the conclusion that if you just want to more quickly dry turning blanks, make a dishwasher or refrig kiln...

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## Mike1950 (Mar 10, 2020)

A de-humid kiln is as sophisticated as I am going to get. The one I saw at Bolhke looked like a mini sub. It also looked extremely spendy

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## pvwoodcrafts (Mar 11, 2020)

Mike1950 said:


> A de-humid kiln is as sophisticated as I am going to get. The one I saw at Bolhke looked like a mini sub. It also looked extremely spendy



I like my dehumidify kiln. Been using it for close 30 years. I always air dry before kiln for my own personal use . Virtually no degrade or loss in the kiln

Reactions: Like 3


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## Karl_TN (Mar 11, 2020)

@Mike1950, @pvwoodcrafts, 

Any pics of your dehumidifying kiln setup? Got any tricks for drying really thick turning blanks (i.e. 3 to 8 inches thick)?

Reactions: Like 1


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## Eric Rorabaugh (Mar 11, 2020)

Tricks, yea....time!


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## Mike1950 (Mar 11, 2020)

Karl_TN said:


> @Mike1950, @pvwoodcrafts,
> 
> Any pics of your dehumidifying kiln setup? Got any tricks for drying really thick turning blanks (i.e. 3 to 8 inches thick)?


On road. Will picture when I get home. Not much to see. Drying big blocks, make smaller or be patient

Reactions: Like 1


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## Eric Rorabaugh (Mar 11, 2020)

You ain't texting and driving are you?

Reactions: Funny 1


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## Mike1950 (Mar 11, 2020)

Eric Rorabaugh said:


> You ain't texting and driving are you?


No way. Kathie was driving. My turn now. Have empty trailer, will not be empty at day end.


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## Eric Rorabaugh (Mar 11, 2020)

Make sure you let us see what you pick up so we can be envious as usual. 

BTW mods....we need an envious emoji!!!

Reactions: Like 1


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## Mike1950 (Mar 11, 2020)

Eric Rorabaugh said:


> Make sure you let us see what you pick up so we can be envious as usual.
> 
> BTW mods....we need an envious emoji!!!


Maple burl


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## Eric Rorabaugh (Mar 11, 2020)

Dammit...where's that envious emoji that I asked for!!!!!


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## pvwoodcrafts (Mar 11, 2020)

Karl_TN said:


> @Mike1950, @pvwoodcrafts,
> 
> Any pics of your dehumidifying kiln setup? Got any tricks for drying really thick turning blanks (i.e. 3 to 8 inches thick)?




Not much to see. 16 x 12 insulated to the hilt
Never dried anything thicker than 4 inches but Like I said I like to airdry first. I have always been in it for quality not quantity.Like Mike said patients. you rush it you get cracked stock

Reactions: Agree 1


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## Mike1950 (Mar 11, 2020)

5x6x12 also insulated well. 70 at dehumidifier.box fan. Cheap indoor outdoor thermometer. I like to keep at 80 in beginning. As water comes out temp tends to rise. Dehumidifier creates enough heat on it's own unless below 20. Have an oil/electric heater and a halagon light to get to 135 for bug kill.


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## TXMoon (Mar 11, 2020)

Karl_TN said:


> @Mike1950, @pvwoodcrafts,
> Got any tricks for drying really thick turning blanks (i.e. 3 to 8 inches thick)?



The blocks I get from online wood retailers are all coated in wax. The ones I have cut myself at home I paint with Anchor Seal. I am sure you're doing that already. I have seen where people take old refrigerators and hook up dehumidifiers to them. Seems more work than I am willing to do now. Here is the videos I watched. Just look up "DIY home wood kiln" in YouTube and have fun.


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## pvwoodcrafts (Mar 11, 2020)

I might add that I have a NYLE system

Reactions: Like 1


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## pvwoodcrafts (Mar 11, 2020)

I have dried green 4/4 before. 1600 bd ft White pine. Took out 53 gallon water in day and a half. Had to keep checking it so it didn't overflow my tub. I normally get 40 to 60 gallon out of a load of air dried hardwoods. Usually have it in for 2 weeks with stress relief procedure. Run it to 135 degrees 2 days in end to kill bugs and eggs

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## Mike1950 (Mar 11, 2020)

pvwoodcrafts said:


> I have dried green 4/4 before. 1600 bd ft White pine. Took out 53 gallon water in day and a half. Had to keep checking it so it didn't overflow my tub. I normally get 40 to 60 gallon out of a load of air dried hardwoods. Usually have it in for 2 weeks with stress relief procedure. Run it to 135 degrees 2 days in end to kill bugs and eggs



Your system is much more sophisticated than mine. It drains outside. Mostly dry burl.


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## trc65 (Mar 11, 2020)

Kevin, type of freezer/ dishwasher dryers I've seen usually use just a lightbulb in the bottom for dry heat and a few holes in bottom and top for ventilation. Air movement through convection. Some I've seen use 12v computer fans if condensation builds. 

Don't remember the wattage of lights, but less than 100 W for most unless your fridge is outside with freezing temps.


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## pvwoodcrafts (Mar 11, 2020)

Mike1950 said:


> Your system is much more sophisticated than mine. It drains outside. Mostly dry burl.


I opted to recover the water to help keep track of how much was coming out. The kiln came with a drying schedule with max water output per 1000 bd ft of lumber to prevent degrade. In all the years of drying it has never let me down

Reactions: Like 1


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## Mike1950 (Mar 11, 2020)

pvwoodcrafts said:


> I opted to recover the water to help keep track of how much was coming out. The kiln came with a drying schedule with max water output per 1000 bd ft of lumber to prevent degrade. In all the years of drying it has never let me down


They are a very nice system.


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