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. Woods are Macassar Ebony and Cocobolo. Anyone have recommendations on how to dry these in a reasonable time frame weeks vs months if possible.

Thanks

[Maurice Mcmurry]

I have the same question and have been trying to learn about the vacuum kiln.

[Edward Weber]

Your choice of woods, which you don't mention, could determine how fast you can dry the blanks.
I would go out on a limb and say that uniformly drying anything that thick will take longer than weeks without some type of forced drying.

[Dale Osowski]

Oops, Macassar Ebony and Cocobolo.

[Richard Coers]

Isn't drying Ebony like drying a rock? Weeks will definitely be out, Im thinking at least 6 months to a year. What is the moisture now?

[Dave Mount]

I would not expect Macassar ebony to be a good choice for planes. Although the wood database does not report shrinkage values for Macassar specifically, other woods in the ebony genus have very high shrinkage rates, which is not a generally desirable characteristic for plane wood. Cocobolo on the other hand has exceptionally low shrinkage rates. You can look them up here: https://www.wood-database.com/

Dense woods are generally difficult to dry in thick stock; their density inhibits internal moisture movement and leads to surface drying over a swollen interior, which is what in turn leads to checking. This characteristic also comes into play on an ongoing basis as seasonal relative humidity shifts cause imbalances in moisture content between the interior and exterior. Wood with low shrinkage values blunt this problem.

There is no easy way to dry thick blanks of dense wood quickly. They are heavily waxed for that very reason -- if they lose moisture from the surface too rapidly, they will check. The way to get moisture to move within wood more quickly is heat, but heat alone will actually make things worse, as it also lowers relative humidity, which speeds surface evaporation (which is a bad thing in this case, because it's what causes checking).

Commercial kilns work by heating wood to speed internal moisture migration, but at the same time maintaining high relative humidity and thereby keeping surface evaporation from getting too far ahead of internal moisture migration. Typical kiln schedules are for high heat (e.g., 180 F) and high moisture (e.g., 80% RH) until moisture content falls to the mid-20% range, then slowly stepping down the RH over time. The rate of the stepping down is dependent on the characteristics of the wood, generally the denser the slower. You can find kiln schedules for tropical hardwoods online if you do a little searching.

You could create a chamber in your shop to mimic kiln conditions, but it's fussy and barring the purchase of expensive control equipment, likely to be pretty labor intensive (lots of checking and adjusting). The most straightforward way is to build a chamber that you can heat, then put a hygrometer in the chamber to monitor humidity. When you initially heat the chamber, wet the interior down so you maintain high humidity as you bring the heat up (the blank would already be in there, with the wax removed -- might be a good idea to keep a thin coat of wax on the end grain). Assuming the initial relative humidity is above 80%, vent some of the interior air and replace with room air to bring the RH down to, say 70%, then let it rise over time to something like 90%, then repeat the process. This will not be a fast process. Initially the humidity rise will be from drying the chamber out, but after that the source of water will become the blank of wood itself. Once the rate at which the humidity recovers from 70% to 90% slows significantly, you can move the humidity interval down some. Obviously a humidistat is a better way to do this, but that involves more expense and fabrication. You can also use a small amount of dessicant in the chamber as a means to remove water, but however it's done, the need is to keep the RH controlled. And, since it's a bit of a seat of the pants simulation of a proper kiln, you could still end up with a checked blank.

Having said all that. . .a much easier approach is to use wood you can buy already dry. Your initial choice of woods suggests to me that "bling factor" is a not insignificant part of your vision. Nothing wrong with that, but it sticks you with the problem of finding conditioned stock in the appropriate size/thickness. Unless it really kills your enjoyment, I would suggest switching to purpleheart. It moves a little more with moisture than does cocobolo (but still way less than ebony), is of comparable hardness, and is relatively easy to find in KD stock. Here's one source:

https://www.turningblanks.net/collections/3x3x12-wood-turning-blanks/products/3x3x12-kd-purpleheart-wood-spindle-turning-blank

I've no affiliation with them other than being a customer. This vendor will also do special orders for longer stock if you need it, though there may be wait.

Hope this helps.

Best,

Dave

[Dale Osowski]

Thanks for the detailed info Dave! Correct, I'm looking at the Ebony & Cocobolo for the bling factor. I've had good luck with the 1,5"x1.5" Gaboon Ebony I've been using for the apron planes but it has been in climate controlled storage for 8 years. The blocks I'm considering are from Bell Forest Products, these would be rift cut blocks so I'm still thinking about giving them a try for my personal prtotype planes and see how it goes from there. Since I'll only need a couple blocks at a time I'm thinking about building a small kiln / chamber as you mention. Still thinking about if it would all be worth it to build these planes. Luckily Thanksgiving break from the day job will give me time to spend in my studio making the apron planes and giving more thought to the larger planes and drying blocks.

Thanks for the replies guys!

[Reed Gray]

Well, I don't have any wood hand planes yet. You might ask this question on the Neanderthal forums. There is a Japanese type of oak that they prefer for their wood planes. I did give a chunk of Lignum to a friend for him to make a hand plane out of years ago. I would want as straight of grained wood as you can find, mostly because any curved grain or angled grain will move in different directions. No clue how ebony will move, but I would expect it to also move along grain directions. I can't say that I have seen any cocobolo that was straight grained. You might be able to use desert iron wood. I think mesquite might work also. Black locust or osage? Boxwood if you can find it big enough. You might be able to rough out the shape, and seal the blank again to let it dry more. I would want it pretty much bone dry before starting, or maybe better to be at equilibrium with your shop. I don't think I have seen any that were glue ups, but that could work as well.

robo hippy