Drying Waxed Blocks

[Dale Osowski]

I'll be making larger Krenov style planes soon and my choice of woods for these planes are mostly only available in waxed 3x3x12 blocks. Anyone have recommendations on how to dry these in a reasonable time frame weeks vs months if possible.

I'll post this in turning forum as well.

Thanks

[Jim Becker]

The thread on vacuum kilns might be of interest to you because of the time frame you desire.

[Cameron Wood]

Figuring that the wood blocks are nominally dry, I would let them sit for at least 6 months, then rough mill and let sit for another period of months.

[John K Jordan]

I have no simple answer. Much depends on the type of wood and the starting moisture. Some blanks are soaking wet under the wax; some are almost dry. I know one wood dealer who always dips blanks in paraffin regardless of if they are wet or dry - they look and sell better that way.

Some species, especially very dense and heavy, must be dried slowly. 3x3s from some species can dry quickly, others can take many months or years.

I dry many hundreds of turning blanks. Some I cut from green wood and seal myself. Some I buy have been dipped in paraffin. If covered in wax the moisture gradient through the blank is likely stable so if you want to know the moisture content in the center of the blank you can use a moisture meter on the surface, but some types can be tricked. For more accuracy, cut out a small sample and measure using the gold standard, the oven dry method. If that shows dry enough, you are done.

A much easier way to judge dryness requires more patience but is accurate: weigh accurately and record the weight in grams and date. I write these on tape on the side of the blank. Periodically (every month or so) weigh again. When the weight quits changing the blank is dry. Note that the air drying time will also depend on the temperature and humidity. (My shop and wood storage area is in a heated/air conditioned space.)

Unfortunately this can take many months or even years. Some ways to speed it up - after waiting “some time” I use a card scraper and wire brush to remove some or most of the wax. (I always do this with olive, ebony, african blackwood and some other rosewoods.) I some cases I melt the wax with a heat gun and wipe it off with a cloth or psper towel. Sometimes I skim the sides with the bandsaw to cut away the wax. Then start the weight monitoring again. Unfortunately, how long to wait before removing the wax is a judgement call based on experience.

Some people use the microwave method to speed up drying: heat the wood in the shop microwave (might not want to use the one in the kitchen.) This can work very well or destroy the wood from the inside out! Look up microwave drying for details. When I did it I heated the (unwaxed/dewaxed) wood only until it was warm on the outside, then let it cool completely. Repeat many times. Monitor the weight. When I did this it usually took hours. Understand that if heated too much at once wet wood may burn internally or even catch fire.

Another method not used much today is boiling the wood. It seems counterintuitive but boiling can stabilize some naturally unstable species and accelerate drying. At one time I purchased large turning blanks (e.g. 8x8x12 or so) imported from Iquitos, Peru. The dealer told me some must be boiled, in particular Pink Flame, or they will self destruct. He said they always boiled bowls and such before exporting. Years ago wood expert Steven Russell wrote about his research and experiences about boiling (and other methods) but his writings are no longer available except on the Internet Archive and in the files of those who saved them.

There is traditional kiln drying, however that is usually done in large batches of similar species. There are vacuum kilns and some woodturners swear by refrigerator kilns gently heated by incandescent light bulbs - humidity in the enclosed space keeps the wood from deteriorating by drying too quickly. There is freezer drying. However, I have no direct experience with those. I stick with air drying with weight monitoring - it is so simple and always works, but requires patience.

JKJ


I'll be making larger Krenov style planes soon and my choice of woods for these planes are mostly only available in waxed 3x3x12 blocks. Anyone have recommendations on how to dry these in a reasonable time frame weeks vs months if possible.

I'll post this in turning forum as well.

Thanks

[roger wiegand]

I've always wondered about freeze drying wood. Unfortunately I no longer have access to a good size lyophilizer to test it out. You need a good enough vacuum pump to pull a very hard vacuum (<0.01 torr) and a trap that will cool to about -60 degC to condense the volatilized water, so not real conducive for a lot of wood. With the high vacuum the water freezes at room temperature or above and then is released by sublimation. The advantage would be that the object shouldn't change shape as the solid water is extracted, plus it should be relatively quick.

[Dale Osowski]

Thanks for the great replies guys!