Drying wood with Silica gel

Some time back a woodturning friend had a brainwave when his wife bought some silica gel (which is, in fact, in bead form) for drying flowers. He thought if it could dry flowers, why not wood? He presented the idea to the guild, citing a couple of small plates as examples of the success he had achieved.  When I dry wood for re-turning or to completion I use both the “shelf” method and the microwave (I have my very own :)) depending on my need for speed and of course size. Mostly I use the microwave for hollowforms and tubes while large bowls and platters get the “bag and switch” treatment if they are of any size. My issue with the latter is that I am not that disciplined that I monitor things religiously enough over long periods. The microwave on the other hand  can be a bit too aggresive requiring each piece to be monitored carefully during the process. The silica gel seems to be in between the two methods so adding it to my arsenal seemed like a good idea.  

Silica Gell sold by Lee Valley

I purchased a small jug of gel from the Lee Valley Tools gardening catalogue. Lee Valley’s gardening section – to me at least – goes completely un-noticed. I did not inherit my mother’s green thumb nor her love of mucking around in the garden. Nor was she able to instill any horticultural desires through endless hours of forced weeding; I preferred my father’s shop.  But I digress. The gel is available in 2 Kg. containers for about $20+ dollars, as I recall. The instructions include three methods of use: “air” drying, oven drying and microwave drying. Basically, the air method takes 5 or more days, the oven method requires a few hours and the microwave even less. The air dry method is much faster than traditional “shelving” methods, the microwave method adds a greater element of control and the oven method is – to me at least – a new tool completely. All three require a container to hold both the piece and the gel, so obviously it needs to be compatible with said shelf, oven or  microwave.  A word of advice: although various kitchen bowls might be ideal from your perspective, that view will probably not be shared by all in the household. Like the  microwave – you may have to get your own :(. The piece must be completely covered so the container should be just large enough to accept the piece and of course you must have enough gel to cover the piece: you may have to buy more than one jug. 

My first venture was with a small hollowform turned from green, spalting Arbutus turned to about 1/2″ wall thickness with a fairly large lump of wood where it had been chucked. It was a shot in the dark because the wood was quite spalted. I kept it in the material for 5 days as per the instructions (for drying flowers). It had lost all its weight in water because reburying it for another few days caused no additional change in weight. There was about the same change in dimension as I would have expected in any other drying method but unfortunately there was a crack through the large chucking mass which could be expected (it dried slower than the thinner portion).  The only thing left was to reconstitute the gel by drying in the oven. All in all, not a bad first experiment considering the short drying time.  

Next effort I will fill the vessel with silica gel but also bury any portions that have a heavier cross section so that water is pulled from that portion at about the same rate as the thin portion. Hopefully drying in this way may not cause the uneven shrinkage.  

As always, I encourage your comments and questions, so please refer to the tag line at the bottom of the article to post a comment.  

 

About Ed Pretty

I am a professional woodturner, specializing in gallery work, commercial work, teaching and demonstrating. I have been turning since 1958, so... a long time. I use this site to present my work to the public at large and to let people know that I am available for teaching private lessons in woodturning. Wood turning is one of my passions (the other is motorcycle touring). It is my desire to pass on everything that I have learned over the years to others so that the craft of woodturning will grow.
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7 Responses to Drying wood with Silica gel

  1. Kevin Roy says:

    DO YOU THINK ALLOT OF DESICCANT LIKE SILICA GEL WILL WORK WELL WITH LOGS 18″-24″LONG x 15″-18″ ACROSS . 1 YEAR PER INCH IN THE RACK IS A LONG TIME (15 YEARS ? ) I NEED TO TRY TO SPED THIS PROCESS UP A LITTLE. THANKS K.ROY

    • admin says:

      Hi Kevin,
      There is no way of drying something that large in any amount of time without some sort of damage. I will be able to help you if I know what you are trying ot make. I’ll email you so we can discuss this further.

  2. joel says:

    hi ed,

    is there any update on the silica gel method for drying wood ?

    what in your opinion is still the preferred way for drying wood? Denatured alcohol? mirowave? boiling?

    Thanks

    Joel

    • admin says:

      Hi Joel,
      I tried the silica gel method a few times and found it to be quite satisfactory. I originally tried to totally bury the piece which took quite a bit of material. I have since found that not nearly that much is required. On the other hand, since this is for finish-turned pieces, I normally turn pieces to finish wall thickness and dry them in a paper bag. It doesn’t take much longer. I turn a lot of hollowforms so there is no real need for a piece to be deadly round, unlike something that would have a lid. Recently I have been drying my wood prior to turning if it is three inches thick or less. If you look further in the blog you may have seen the driers that I built using an old fridge and a scratch-built one using a dehumidifier. I get the wood down to anywhere from 6% – 12% from 40%+ in 2 – 3 months. I prefer 12% because most pieces will rehydrate to that anyway and the wood turns much nicer. If I turn something from larger dimension and want it to be round, I find that rough turning (finished wall thickness plus at least 10% of diameter), coating it with wax emulsion and setting it in my drier for a couple of months before re-turning it is more practical. Remember when using this method that the key is to have as even wall thickness as possible. A large knob on one end (say, for a tenon) will cause a crack. Most of my stuff tends to be too large to use silica gel in reasonable quantities. It’s forte is with smaller pieces.

      I have never tried using alcohol – because of the volume issue and alcohol is nasty if it catches fire (because you can’t see any flame) – but I have a friend who prefers that method. He brings home denatured alcohol by the pail from where he works. I’ve never boiled my pieces for a couple of reasons. First, it’s more suitable to a production set up where you have a large number of bowls to go at once. I never have a huge amount of rough turned work to make it worthwhile to fire up a kettle for the time it takes to boil. It’s expensive unless you’re burning up a bunch of crappy old wood. The other reason is that I have turned a few pieces from a fellow that was unloading a bunch of boiled quilted maple blanks. Quilted maple can be a bear for tearout but these were unbelievably bad. My suspicion only, but I think you can over-boil a piece. The objective is to heat the wood and soften the lignin allowing the wood to slide, thus releasing the tension. I think that the lignin is altered enough that it can’t even hold the wood together any more. Just my theory, but I didn’t like turning it at all.

      Thank you for following my blog. I enjoy the fact that you are finding the information of at least some value. 🙂

  3. joel says:

    Thank you ed for the quick reply.

    Your insights are very useful and informative.

    I will try the silica gel method.

    Warm regards

    joel

  4. Guillermo Armenteros says:

    I have a 2 inch thick by roughly 40 inch long board routed out for cutting. Any suggestions on using silica gel or something? The body portion of the instrument is about 14 inches thick and neck area about 4 inches thick. More detailed information and pictures can be found here (Sorry for linking to another page but couldn’t post pictures in my comments here)

    http://www.talkbass.com/forum/f57/headless-5-string-35-scale-bass-tree-bass-880653/

    Any recommendations?

  5. Yuval Yeoman says:

    Hi Ed
    I found your site after talking to Dane Spence. He is thinking about starting turning and might buy my old Harbour Freight lathe for a starter lathe. Anyway, I have tried all kinds of methods of drying, but one I am finding particularly good at this time of the year is a kiln I made out of an old dishwasher. I installed a thermostat, small fan and a 200watt ceramic bulb type element with a humidity and temperature gauge outside . I set the thermostat at 100 degrees for three days and then turn it down to 90 for three weeks. I can have 3x3x12 spindle blanks down to 10% in that time. I turn my bowl walls to 1/2 inch thickness, boil them for an hour and follow the same process as the spindle blanks. I get the usual warping but rarely any cracks due to the boiling. Hope this info. is helpful to someone.

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