Drying Logs in a Vacuum Kiln

      Heavy timbers dry rapidly in a vacuum kiln. October 26, 2013

Question
Are there any schedules available for drying 24/4 white pine? This material will be used in log home construction. I was told the desired final MC is 18%. Also any indications on how long from green this will take to dry?

Forum Responses
(Sawing and Drying Forum)
From Professor Gene Wengert, forum technical advisor:
Any chance you could drill a large hole lengthwise through the center to make drying easier and reduce weight? Are a few checks okay? Or maybe you can kerf it? Do you want 18% MC in the core, so that the shell will be somewhat drier? Or is 18% an average?

As 12/4 would take around 3 months, I would guess that 24/4 is no less than 7 months for a quality piece and possibly longer. For that reason, we would expect to air dry first for nine months or so before going into the kiln.


From contributor D

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I'm sorry to be always making crazy sounding claims, but a vac kiln can dry 6" pine squares to 18% in about 6 days. Heart center means a crack at least on the side nearest the pith.


From Professor Gene Wengert, forum technical advisor:
Indeed, I should have mentioned vacuum drying as a reasonable option.


From the original questioner:
Thanks for the responses. The customer told us that someone else who was drying this previously was doing it in 21 days. Quite frankly I have a hard time believing that, but that's what they claim. I must believe they are tolerant to checking. With this material being used in log home structure I think they would not want large open splits.

The core target is 18%. I don't think drilling out the core would be an option but it might be worth asking. We need to go visit these people and see the condition of the material they already have. Also do some sampling while we are there to confirm MC.



From contributor L:
We have a great many kilns installed drying eastern white pine for log homes. The most common sizes are 6x8 and 8x8.

They should be dried in 1-1/2" stickers. The usual standard is 15% at a depth of 1-1/2". Several mills dry in two weeks and sell all they can produce. Others take 4 weeks and the longest I know took six weeks. The pine is going to check any and people don't seem to mind. One mill pressure treated logs with PEG and didn't dry. The logs didn't shrink. I think they are closed now.


From contributor D

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15% at a depth of 1.5" is interesting. When I was experimenting with softwood beams, I was getting 15% at the core. I'm currently working on a kiln for installation in Russia. They want to dry 40' squares for log homes. I was recently reviewing some old process logs and saw one where I got the beams dry in 2.8 days. That's less than 3 days to get the core under 20%.


From contributor E:
Wow… How big is the log home if each log is 40' square?

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  • KnowledgeBase: Knowledge Base

  • KnowledgeBase: Primary Processing

  • KnowledgeBase: Primary Processing: Kiln Operation


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