Microwaving wood to dry it

[Neil Lawton]

I have an inherent mistrust of wood moisture meters, or rather hobby or craft ones, I had one and the moisture readings were incredibly unreliable when compared to the industrial meters we had at our factory. We used to buy in supposedly kiln dried. To complete the drying process we kiln dried the wood for six weeks. Once it was dried if it was to be fir rated it was put in a vacuum for twenty minutes and the vessel was flooded with a magnesium chloride solution and the pressurised for twenty minutes. The pressure chamber was drained and a vacuum reset abolished for a few seconds to remove excess moisture. The slats, at 25mm thick we're then placed back in the kiln for another six weeks to get the hrs down to 14% max.

I find it impossible to believe that the centre of a decent size blank could be dry other than after a significant period or either air or kiln drying, but as always I remain open to being convinced!

Interesting.
Do you now have this equipment at home now,to test your wood, or do you use another method!
I do agree that cheap moisture meters are not that reliable, but they are indicative of moisture loss!
I don't work in a controlled environment, as I'm sure you don't, through experience though an indication of between 14 to 16% on the particular one I have has continued to give good results with pen blanks. The rest is through experience only.

The fact that you state that this is impossible to believe, I find quite astounding. The whole principle of drying wood is to relieve it of its moisture content in a controlled way. Wood will always lose moisture from its surface area, whether it is kiln, air, or microwave dried.
A modern build centrally heated house can now have an EMC as low as 8% so every ones figures could be considered out of date
Apologies to PhilH, didn't mean to hijack your thread

 

[Neil]

Interesting.
Do you now have this equipment at home now,to test your wood, or do you use another method!
I do agree that cheap moisture meters are not that reliable, but they are indicative of moisture loss!
I don't work in a controlled environment, as I'm sure you don't, through experience though an indication of between 14 to 16% on the particular one I have has continued to give good results with pen blanks. The rest is through experience only.

The fact that you state that this is impossible to believe, I find quite astounding. The whole principle of drying wood is to relieve it of its moisture content in a controlled way. Wood will always lose moisture from its surface area, whether it is kiln, air, or microwave dried.
A modern build centrally heated house can now have an EMC as low as 8% so every ones figures could be considered out of date
Apologies to PhilH, didn't mean to hijack your thread

Got me a bit wrong there Neil, I agree that it will assist the wood to lose moisture but, in the case of Phils blank, half a pint of water is a lot to lose and from the depths of 520KG/m3 wood. I agree with your point about cellular collapse as a result of the microwaving and it is this which leads me to comment about the ability of a micky wave to dry the wood. At the outset of the kilning process, water is introduced into the kiln environment to allow the cellular structure to open, like having a good sweat in the sauna. Kind of aclimatises the wood to the higher tempreature before the humidity is reduced to allow the wood to shed water. To make the wood dry there must be a moisture content gradient through the wood, ie the outside is drier than the inside. What I find impossible to believe is that the process described can create, and or maintain that gradient long enough to remove nearly half a pint of water. As a member of Trada I will give them a ring next week and talk to their technical guys and see if they have a view. I have a whole heap of fresh cut sycamore and will give it a trial over a week or two and see if we can come up with some concrete evidence, you never know I might be the next pope?

 

[Penpal]

Got me a bit wrong there Neil, I agree that it will assist the wood to lose moisture but, in the case of Phils blank, half a pint of water is a lot to lose and from the depths of 520KG/m3 wood. I agree with your point about cellular collapse as a result of the microwaving and it is this which leads me to comment about the ability of a micky wave to dry the wood. At the outset of the kilning process, water is introduced into the kiln environment to allow the cellular structure to open, like having a good sweat in the sauna. Kind of aclimatises the wood to the higher tempreature before the humidity is reduced to allow the wood to shed water. To make the wood dry there must be a moisture content gradient through the wood, ie the outside is drier than the inside. What I find impossible to believe is that the process described can create, and or maintain that gradient long enough to remove nearly half a pint of water. As a member of Trada I will give them a ring next week and talk to their technical guys and see if they have a view. I have a whole heap of fresh cut sycamore and will give it a trial over a week or two and see if we can come up with some concrete evidence, you never know I might be the next pope?

Be careful Brian suggests defrocking to some people.

Peter.

 

[PhillH]

Interesting thread this and some good reading, I may just give it a go using the 30 second at a time method and see what happens.

Thanks all for the input, much appreciated.