Freeze Drying

[Reinier]

Hi,

I've heard about putting green wood in the freezer to "season" it and as I have plenty of unseasoned wood and an empy freezer compartment in the beer fridge I would like to give it a try. Has anybody got any experience with it? At what stage do you freeze: unturned, roughed out or finish turned? How long do you put the wood in the freezer and do you have to put it in the fridge afterwards? Does it worsen cracks in the wood?

Any experiences welcomed.

Thanks,

Reinier

[RETIRED]

Gooday.

Welcome to the board.

I think that Vic Wood did an article on this in one of the magazines.

I am sure that some one will enlighten you.

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Ian () Robertson
"We do good turns every day"

[ubeaut]

Basically it is for use with bowls, turned and sanded ready for finishing. I am not exactly sure of the times that are required for the process to work but it goes something like this:

Place in freezer for 1 week, leave at room temp for 1 week, place in fridge for a couple of weeks then return to room temp for a week or so before re-sanding and finishing.

This is not the correct method just a rough idea as to what should be done. As said someone else will surely help you.

Cheers - Neil

[Chris Longworth]

Hi Renie.
Some time ago this topic came up one the board & I contacted Vic Wood who kindley replied with this faxed explination of freeze drying.
This is a direct copy of the fax he sent to me (Hope it is of help to you).

"FREEZING, turn wet bowl, sand, then complete. Place in freezer, then refrigerator.

It is not classified information regarding freezing timber, I am more than happy to share my knowledge with you. It works for me, so good luck, give it a try. Bev loves opening the freezer to prepare for dinner, she never knows what is coming out next.

1. Turn outside of bowl, sand to satisfactory finish.
2. Rechuck & complete inside.
3. Use Vacuum plate to remove unwanted chuck marks on base & sand .
A finish of Organoil, Rustins Danish oil or Ureathane can be applied as you finish each section. (One coat only)
4. Place the finished bowl in a plastic bag & put in the freezer for at least 24 hours.
5. Take bowl from freezer, remove plastic bag, thaw out, then place in the refrigerator & this will allow it to dry out gradually. (Must not be in plastic bag).
6.Leave in the refrigerator for up to 10 days, a bowl up to 3/8" thick should dry in this time.

If you wish you can weigh the bowl before putting in the freezer.

The theory is that in the freezer the cells are perforated by the freezing, & then in the refrigerator the moisture is taken out of the wood. (Like bread or meat drying out if it were not covered with Glad Wrap).

If removing form the refrigerator in hot weather it is advisable to wrap the bowl in paper towl, or put it in a brown paper bag, so that the timber acclimatises to the atmosphere slowly. DO NOT use news paper as the print will be absorbed into the timber. Keep bowl in a cool spot.

After bowl has stabilised to normal atmoshpere, cut back with 4/000 wire wool, webrax or a fine scotchbrite mop, then proceed with your mormal finishing of the wood to obtain a suitable luster.
Finally finish with a swansdown mop.

Some woods I have found work better than others, Red Gum, Campher Laurel, & Blackwood, Sassafrass, Huen Pine, all seem to work well, other woods do not crack but may distort.

If the selection of wood is quarter sawn it tends to work more effectivelly than live sawn blanks.

I do not know for sure, but if the wood (bowl) has not been in the refrigerator for at least 10 days, it can even warp after it comes out. This I belive is because all the excess mositure has not been removed. Up till now I have not had one bowl split, but some have worped.

I did have a Red Gum bowl 10" X 1.3/4" with a crack in the edge, & it had warped. It was still wet, I followed the above process & the bowl flattened out, & the crack closed out.

Experement a little to see what happens with the wood that you use. Some species of wood from different areas can also be temperamental.
Good luck, it worked for me, hope it does for you.

Kind regards.
Vic."


[This message has been edited by Chris Longworth (edited 15 September 2000).]

[JackoH]

Reiner. There were some post on this subject a few months ago but I'm blowed if I can find them.
What Neil says is basically right, but it is a matter of trial and error.
I've had some terrific results with silky oak, but lousy with Tas. Myrtle. 1 week in the freezer, 1-2 weeks in the fridge wrapped in a tea towel or similiar,checking the wrapping every couple of days or so and changing it if it becomes wet. Then repeat the process as necessary. You could then turn down a rough shape to check if the moisture content is significantly reduced, if not ,back in the freezer etc. etc.
Good Luck. John H.

[ubeaut]

Hey John what happemmed to you? Took lots of EEE to the Island and you didn't show.

Did you join the ranks of the crookies or was it the thought of seeing me and that made you stay away.

You missed a great weekend. Lots of turning great fellowship and for the bad ones a very wet Saturday night.

Hope you're over what ails you.

Cheers - Neil

[Iain]

Not a woodturner and at risk of sounding pedantic, what sort of fridge/freezer are we talking about? The frost free variety really suck the moisture out of food, more so than a convential. Would this also apply to wood and would it be to the detriment or advantage of the piece in question?

[Chris Longworth]

Hi Iain.
Can't answer the question for you. I only tried it a couple of times using the chest freezer & yes I know it's sacrilege doorstop, but I had to use the beer fridge in the work shop. Carol was not impressed with the idear of the kitchen fridge being used.
Just as a side line, I prefer to mocrwave any wet peices I need to turn.
Chris.

[Marshall Gorrow]

Originally posted by Chris Longworth:
Hi Iain.
Can't answer the question for you. I only tried it a couple of times using the chest freezer & yes I know it's sacrilege doorstop, but I had to use the beer fridge in the work shop. Carol was not impressed with the idear of the kitchen fridge being used.
Just as a side line, I prefer to mocrwave any wet peices I need to turn.
Chris.

>Just as a side line, I prefer to
> mocrwave any wet peices I need to turn.

>Chris.


Hello Chris,

I agree with you. Freezing, boiling and microwaving all free the water that trapped in the cell walls. Most of my wood has been frozen. I live on the Canadian border about 75 miles from Montreal, Quebec in New York State. The microwave is the fastest method to dry wood. As long as you take your time and take it easy, good results can be te outcome.

Much of my turnings are frozen at -30º F. (also C. the two scales equal out at -30º) Most are air dried. But when I am in a hurry, I pop them in the "Mike". If you can get the turnings to dry on the inside before they overdry on the outside they won't split. They will warp but they won't crack.

Get the trapped water out of the inside and prevent the outside from drying too fast and everything else works out.

Boiling and freezing are safer methods; is hard to mess them up. The frostless fridge is an excellent dehumifier kiln. But I, like you, prefer the microwave to free the trapped water.

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Marshall Gorrow
May your next turning be your best!

[JackoH]

Yes Neil, Thanks for your good wishes.I was too crook to come to the island, only a cold , but a real bastard, which I have just rcovered from. Bring your EEE to the WWW Show next month. Unlike thyose mean so and sos on the other part of this forum I will buy you a cup of coffee!
Her indoors is not too keen on the Micro- wave being used to dry wood. I don't blame her 'cause there was a funny taste to food for a day or two after my one and only (aborted) attempt! Since you wrap up wood when freezing or defrosting, type of fridge/freezer should make little difference.
I think the best idea is to send wood to our friend in Canada.
John H.

[JackoH]

Sorry Neil. Forgot to add my congats to you and Ted on your awards. Both well deserved

[ubeaut]

G'day Marshall

Long time no hear. I believe studies done here indicate that there has been a bit of trouble with dramatic collapsing of the internal structure of timber a couple of years after being nuked in the microwave.

This may be because of bad microwaving practices or just because the practice is still really in its infancy and not enough is yet known about it. But is is worth bearing in mind if you are making a piece for sale. Especially if the purchaser knows where you live.

I have nuked a few pieces myself over the years and to date don't know of any trouble with them. However it would appear that more and more the trend here is towards the freezer method.

Personally I love the leathery tecture and feel of a green turned bowl that is wet sanded to 1500 grit then finished with Shellawax Cream and left to dry naturally. I have a number that have been done this way and they are always the ones that receive the most favourable comment. I have never had one split on me and usually only get a very minute amount of warping. I do however turn reasonably thin and keep an even wall thickness throughout. This is a key to this sort of green turned bowl.

Cheers - Neil

[Marshall Gorrow]

Originally posted by ubeaut:
G'day Marshall

Long time no hear. I believe studies done here indicate that there has been a bit of trouble with dramatic collapsing of the internal structure of timber a couple of years after being nuked in the microwave.

This may be because of bad microwaving practices or just because the practice is still really in its infancy and not enough is yet known about it. But is is worth bearing in mind if you are making a piece for sale. Especially if the purchaser knows where you live.

I have nuked a few pieces myself over the years and to date don't know of any trouble with them. However it would appear that more and more the trend here is towards the freezer method.

Personally I love the leathery tecture and feel of a green turned bowl that is wet sanded to 1500 grit then finished with Shellawax Cream and left to dry naturally. I have a number that have been done this way and they are always the ones that receive the most favourable comment. I have never had one split on me and usually only get a very minute amount of warping. I do however turn reasonably thin and keep an even wall thickness throughout. This is a key to this sort of green turned bowl.

Cheers - Neil

G'day Neil,

This will be my third attempt to answer your post. The system keeps telling me that my password is wrong even though it is the one that I have always used. Isn't technology wonderful.

I have been using the microwave to dry turnings for 4 or 5 years, not often but every once and a while. I have a fruit bowl that has been used daily for at least 5 years. No problems what so ever. It is only about 1/8" thick and a little on the thin side for a fruit bowl so I'm sure that a problem would have made itself know.

I don't really see any difference in rupturing the wall by boiling, freezing or microwaving. I don't leave the room while microwaving and have heard the "horror stories" of microwaving on "high" fr 15 minutes or more. Boiling and freezing do have the advantage of being "fool proof"; you can't boil or freeze something too long.

I will have to try finishing green with Shellawax. I have finished green with thinned polyurenthane with no finish problems. (Those pieces were partially air dried and possible would have been frozen outside before the rough turning.) Of course it is impossible to seal moisture in or out of wood. I have even used old finish to seal "finicky" rough turned piece and finish turned a year or two later with no splitting.

Nice talking to you, Neil. Cheers!

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Marshall Gorrow
May your next turning be your best!

[Chris Longworth]

Hi Marshall.
I agree, to take youe time is the trick to microwaveing. I weigh the turning before starting & all thruogh the prosess.
I found that the other important factor is to be sure that the timber has completely cooled between each nuking.
Neil,as for dramatic collapsing of the internal structure of timber, I have a number of bowls that now 3 years old with now signs of such affects.(As yet :confused
Chris.

[Marshall Gorrow]

G'day Chris,

I think that you hit the nail on the head. The Microwave lets you rupture the cell walls to let the moisture out. A little more "nuking" slightly boils that water so that there is actually less moisture in the inside than on the outside. Letting it cool completely lets the whole turning relax and lets the moisture even out through the piece.

Then after it completly cool and relaxes, you start the process over. If you spread it out over several days, it's still the fastest way to dry wood.

I do know one fellow who "nukes" for 2 minutes on high; then after allowing 10 minutes for cooling he puts it in an oven at 150º F for 6 to 8 hours. That's fast also. I think that that puts more stress on the wood. He says that it work well!

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Marshall Gorrow
May your next turning be your best!