Drying cabinet for turning blanks?

[ian maybury]

I've just posted a question on dust collection when turning. The same friend has asked for some help with selecting and installing a set-up to dry turning blanks. Pardon my running two threads together.

I've some background understanding of drying processes and wood moisture content, but am wondering if you guys can offer some advice on how best to approach this question.

He has ready access to baulks of green timber (local ash, oak, elm and the like for the moment - but may well progress to fancier tropical stuff in due course), but no means of drying and/or maintaining stock or work in progress at the required moisture content. (whatever that is - it's presumably much like the situation in cabinetry where perhaps 8% moisture/45% relative humidity is in the ballpark)

The objective is to avoid nasty surprises - both while working, and for recipients of his work. He's not very experienced, but clearly there would not be much point is going with a set up that wouldn't cover reasonably foreseeable demands.

The sort of questions that come to mind include:

(a) Can turning blanks be kiln dried when more or less cut down to size, or is it necessary to dry the wood in larger logs and cut when dry?

(b) Is there possibly the option of running with a small cabinet sized personal kiln? One that could be operated by a guy who isn't into very fine technicalities? Is there possibly such a thing available on the market as a packaged unit? I'm familiar with the sort of humidity and temperature controlled cabinets used for testing in industry.

(c) Can dried blanks and work in progress be safely stored in a reasonably dry and warm workshop? Are there circumstances (e.g. weather conditions) where air conditioning is typically advisable ?

(d) I've seen mention of turning from 'green' blanks - purposely seeking some distortion in the finished work afterwards. Are truly green blanks used in this situation, or is there some partial drying process that is required?

(e) How big a deal is control of wood moisture content in turning vs. cabinetry?

(f) Is there perhaps a recommended handbook/manual covering this ground?

Thank you,

ian

[Bernie Weishapl]

Ian as far as blanks go if turning bowls most leave the walls of the bowl 10% of the diameter. So if the blank diameter is 10 to 12 inches I leave the wall thickness at 1". There are a lot of made up Kilns on the net for woodturning. What a lot of us do here in the States use is a old refrigerator. Use of simple light bulbs and a small fan works great. I store my blanks in my shop but do have a room that is cooler and has little air flow. I store them on the floor. On my bowls, vases, etc. I completely coat them with anchorseal after I put the date and type of wood on the blank. They will sit from 6 months to a year. As far as green blanks go they are easier to turn to rough shape when green. I have had them so green that they sling sap out when turning. So yes truly green blanks can be used. I do turn a lot of my vases or Natural Edge bowls from green to finish in one session on the lathe. I immediately soak with a Danish oil or Antique oil when I take them off the lathe. I try to when I finish a piece after it has been roughed out and then dried is to keep the moisture content at 8% or so. As far as a book the best I found when I started was Keith Rowley's, Woodturning, A Foundation Course. I got the book and DVD. There are plenty of others out there but found this was a great starter set.

Don't know if I answered your questions for you but there will be others chime in and you should get a lot of great ideas from the great group here.

[ian maybury]

Thank you Bernie, some good pointers there. The refrigerator cabinet sounds interesting - am I correct in thinking that it's a case of using a small rise in temperature to drop the humidity in the cabinet to 45% or so, and the fan to move out any moisture released from the wood? That would basically be air drying - so it's probably for keeping wood at the right dryness - in that it probably takes quite a while for a thick blank to dry right through?

ian

[Prashun Patel]

Ian-
There are a couple popular methods for stabilizing green blanks.

Kiln, microwave, denatured alcohol + time, wax + time.

It is my experience (both personal and reading others) that when people come into green wood, it's often several to many logs at a time. For this reason, my inventory of green wood tends to outpace my turning throughput. As a result, I find it easiest to rough them to 10%, and just wax and store my blanks, since it'll be months b4 I can get to them anyway.

I find that I have to watch my blanks as they dry - every couple days, to nip cracks in the bud.

[Jim Burr]

I've never tried Anchor seal, but have received many blanks coated with it. The new formula really sucks! Stick with the Classic formulation. Having said that...I use saran wrap, or plastic kitchen wrap. Cut a green blank round and wrap it in plastic wrap. I have several pieces of Michigan walnut that were received soaking wet. 1 year in wrap and not 1 little check! YMMV and this is not the only way to do it...but it's cheap and easy!

[Scott Hackler]

+1 on the new "green" Anchorseal. YUCK! I have a half a gallon left and and going to buy a couple gallons of the original IF a vendor has some in Waco at SWAT.

That being said, I am a denatured alcohol user for drying. I tried several different ways and that process works great for me and my climate. Anchorsealing and waiting worked great too but it took 9-12 months. The DNA method gives me a dried roughout in about 4-6 weeks!

A local turner uses a fridge with a 75w light bulb and a hole cut low in the door for air intake and a hole in the upper side with a PC fan pulling air out of the fridge. I can't think of how long he said it takes to dry a blank, but it seems like a 3 month or so wait. Now if you take a 10" square block and attempted to dry that...well see you in a few years. :)

[Bob Bergstrom]

I have had more failures from Anchor Seal II than I have had in 30 years. Had some nice 135 oak and old ash crack in the top 3/4 ths. of the blank. 3 coats minimum now.

[ian maybury]

It sounds like there's more than a few options that go well beyond the classic kiln drying approach Prashun + guys. Each no doubt a black art in it's own right. Sounds like it's time for me to do some reading.....

ian

[Jim Burr]

I left out that I use DNA on 10" and under stuff...that's the size of my bucket. It really works well and never had a failure. But!!! Stuff does warp like crazy so make sure you follow the 10% guideline.

[ian maybury]

To ask a duuh question Jim. Do you use these coatings on blanks while they are in the kiln to control the rate of moisture loss? Or is that too aggressive? As in is it possible to kiln dry turning blanks? Or are the sealers used when air drying the blanks either (a) in the air, or (b) in a heated cabinet?

I'm guessing that maybe you have to air dry the blanks first with the help of a sealer, before maybe finishing them in a kiln?

Plan B might be to try to dry more or less a 'log' with the end sealed, and then cut off blanks - but that'd be quite some thickness to dry through so it'd be slow. Maybe other other issues too?

I'm probably installing a Logosol Sauno kiln for use on my own work, and could use that. http://www.classichandtools.com/acatalog/Sauno-Wood-Kiln.html It uses steam drying which apparently reduces the risk of splitting...


ian

[Dennis Ford]

Kiln drying is not as important for most lathe work as it is for cabinet work. Drying blanks that have not been roughed out will be very frustrating. My suggestion is to spend time roughing out blanks instead of worrying about a kiln. The elm rough-outs will dry safely in a paper bag, oak is more tricky and I have had better success when it is turned to final thickness and allowed to warp.

[ian maybury]

Definitely black arts territory Dennis - sounds like my man is going to have to do some learning, that a one size fits all solution is fairly unlikely...

[Peter Hay in Aus]

Re Blank Drying,

I dry my Pen Blanks in my roof space in my hallway installed a pull down ladder 30 seconds in the roof. I cross stack dry them it is controlled drying no direct heat from wet to dry in a few mths max.

Talking to my wife about this years ago and never accurately measured moisture content I handed her known dry and wet then not ready blanks known to me marked with a number she picked the right ones every time by feel her method wet or not ready feel colder or damp never missed myself since.

Another method success was using a few numbered blanks from each species weighing on a weekly basis single blanks when stable for one week, ready for me.

The initial installation of the ladder was to quickly detect and source of roof leaking and to make it easy in my old age( now) to instal pp,s or extra lights at will ( I am an Electrician).

Recently dropped out my old pics but have dried 500 pen blanks at a time this way.

Have success Peter.

[Anthony Diodati]

I've never tried Anchor seal, but have received many blanks coated with it. The new formula really sucks! Stick with the Classic formulation. Having said that...I use saran wrap, or plastic kitchen wrap. Cut a green blank round and wrap it in plastic wrap. I have several pieces of Michigan walnut that were received soaking wet. 1 year in wrap and not 1 little check! YMMV and this is not the only way to do it...but it's cheap and easy!

Your post reminded me.
I wanted to ask again if anyone knows for sure what the Rockler end grain sealer is.
I hope it is not the new anchor seal?
How can I tell?
I put some on some wood the other day when it was warmer, but I put some of it on some wood today, and it is still not dry.
It's a lot colder today.
Does the temperature make a big difference in the drying time of the rockler sealer?

[Anthony Diodati]

What brand DNA are you using?
So this fridge with a 75w light bulb.............. set-up, he is drying whole blanks, not roughed out turnings?


+1 on the new "green" Anchorseal. YUCK! I have a half a gallon left and and going to buy a couple gallons of the original IF a vendor has some in Waco at SWAT.

That being said, I am a denatured alcohol user for drying. I tried several different ways and that process works great for me and my climate. Anchorsealing and waiting worked great too but it took 9-12 months. The DNA method gives me a dried roughout in about 4-6 weeks!

A local turner uses a fridge with a 75w light bulb and a hole cut low in the door for air intake and a hole in the upper side with a PC fan pulling air out of the fridge. I can't think of how long he said it takes to dry a blank, but it seems like a 3 month or so wait. Now if you take a 10" square block and attempted to dry that...well see you in a few years. :)

[Aric Krueger]

Here are some thoughts, personal observations/experience, and info from me that I hope you find helpful/useful.

Turning blanks can be cut rectangular and the end grain sealed with a microcrystalline wax emulsion (Anchor-Seal by the UC Coatings Corpoaration being one of the several available). Use the end grain sealer as soon as possible after the tree has been cut. Moisture escapes from end grain faster than side grain. Sealing the end grain evens out the moisture loss rate through all sides of the wood. Cut your blank using the 10% rule for most species of wood. i.e. cut them 10% wider than long as the blank will shrink more in width (side-grain/side-grain) than in length (end-grain/end-grain). I advise keeping them no more than 4" thick; beyond that, the percentage of cracks greatly increases. Avoid including the pith (and knots if you can) Cut about 1" away from it for most species. Small trees with tight circular growth rings (or boards cut close to the center) will likely have more knots, cupping and possibly crack more than large trees with less curvature of growth rings across the boards end grain. Quarter sawn boards are the most stable. I do not recommend leaving the log whole as it will crack (probably multiple cracks).

When rough turning a blank, again use the 10% rule of thumb for most species. which is to leave the wall thickness at least 10% of the diameter. example: a 10" dia. bowl is rough turned to leave the wall 1" thick. For more unstable species, that rule will have to be adjusted. Pacific Madrone, I have found to be 16-18%. There are charts available for this on the internet; the parameter you want to look at for this is the tangential shrinkage for flat sawn boards. For rough turning, the height can exceed 4" without significant cracking % increases. {The pith may be able to be included in a rough turned blank if the drying characteristics of the species of wood you are using is favorable to it. Observe wood shrinkage charts on the internet, when the ratio of tangential/radial shrinkage is closest to 1.0 for a given species, the movement is symmetrical and is less likely to crack with the pith in.}

I usually boil the rough turning 1 hr for each 1" of wall thickness and coat only the outside of the rough turning (others coat both sides) with Anchor-Seal and place in a paper bag in the house. I weigh it periodically on a scale capable of 0.1g increments and when it stops loosing weight, I know it has stabilized with the relative humidity indoors. Measurements have shown me that this is 4-6% MC. It usually takes about 3-6 months for a 1" thick rough turning to dry this way. Without boiling, it seems to take longer, about 6-12 months. (I don't know why that is, it is just an observation I have made). The dried rough turning is then returned to the lathe and a finished product is produced.

Sometimes turners make the finished thin-walled product straight from green wood. The intention is that the resulting warping is part of the art. It would not be able to be returned to the lathe after it has dried and warped as the walls would then be too thin and trying to bring it back to round would cut completely through on the longer sides of the oval. The use of a mesh type sandpaper is necessary as very wet wood tends to clog regular sandpaper.

In either case, rectangular blank or rough turned, I recommend air drying the wood down to around 20% moisture content (or less) before kilning it the rest of the way to 4-8% (indoor use for most of USA) unless you can make a kiln that temperature, humidity and air flow can be controlled and you have the information you need for the species you are kilning. (which I have provided a link to below)

Drying most species of wood above 20% MC just using heat and air flow usually results in high percentages of wood cracking as the rate of moisture loss is too fast and the MC is too uneven throughout the thickness of the wood. Commercially, many species of wood are kilned down to a certain MC, steamed at high heat for a specific period of time and then kilned to the final desired MC. The steaming reduces stresses in the wood which results in less cracking and reduces saw kerf binding for the end user.

65°F at 60% relative humidity (or something close to that IIRC) is considered about ideal conditions for air drying most species of wood that is stickered to allow air flow. Air drying outdoors (in a shed) in most of the USA will result in 15-20% average MC. That's good for rough construction but wood used at this MC for cabinetry or turning (indoors use) will result in noticeable movement. (Very bad for lidded boxes!) General rule of thumb is 1 year for each 1" thickness of the board (and some say +1 year) for air drying green wood to completely stabilize with it's environment. (Again, that being 15-20% MC outdoors and 4-8% MC indoors). A four inch thick board will take 4-5 years to stabilize with its environment.

Dried blanks and WIP should be stored indoors to maintain the MC if the end product is to be used indoors. If the intention of the end product is to be used outdoors, it is probably OK to leave it outdoors (assuming it is covered but has free air flow, off the ground, and out of the rain/snow).

The smallest kilns commercially available that I have seen are about 10'W x 14'L x 8' tall, are somewhat complicated/sophisticated to operate and maintain and are pretty expensive. As has been said, there are many plans on the internet for building small kilns with light-bulbs, fans and/or house-hold dehumidifiers. Even low cost solar wood kiln plans are available. (In remote parts of the world, solar kilns are commonly used.) I've used a kitchen food dehydrator (when the wood is below 20% MC,) with great success. In fact, often times, the wood gets over-dry. I have to leave the blanks/rough turnings in the house and periodically weigh them until they stop gaining weight.

You can find the USDA Forest Service Dry Kiln Operator's Manual here:
It consists of 12 downloadable .pdf's (11 chapters and the intro, index, glossary).

http://www.fpl.fs.fed.us/products/publications/several_pubs.php?grouping_id=101&header_id=p


Other USDA FS publications in .pdf form you may find useful:

http://www.fs.fed.us/ccrc/topics/urban-forests/docs/physical%20properties%20and%20moisture%20relations %20of%20wood.pdf

http://naldc.nal.usda.gov/download/CAT87208732/PDF (air drying)

This ain't bad either:

http://www.lignomatusa.com/images/Docs/LignomatPrinciplesPracticeDryingLumber.pdf

I know that was long winded! Sorry! I hope that it helps. Happy turning! :)

[Fred Belknap]

If I understand your question you are asking for a way to dry turning blanks not rough turned bowls. I cut my own bowl blanks out of downed timber, cherry, ash, walnut and some others. I cut into about 18" sections and then split lengthways. I coat the ends with anchorseal and store in a dark dry place, like my barn. The blanks dry out some what, to the place that when turned they don't sling moisture. I so far haven't found a way to dry them completely. After six months to a year they start to crack and many of my nice blocks end up as firewood. Now roughed out bowls I have pretty good success with DNA then anchorseal the outside and leave the inside open and put shavings in them for about a week. I weigh the rough outs and when they stop loosing weight I consider them dry, they usually read less than 12%. If I am in a hurry I will microwave a rough out, and that is another story.

[jwjerry w kowalski]

I have a homemade kiln like the one that Scott Hackler commented on. I can dry a bowl in 3 weeks with it. I made mine out of plywood with the shelves having an outside frame and the rest being chicken wire so the air can flow around the bowls that are sitting there. It has a light bulb on the bottom left side and a low wattage fan mounted over a hole on the upper right hand side.

What I do is load it up with bowls that have been roughed turned to 10% of their diameter, then turn the fan on for the 1st week, the 2nd week, the fan is still on, but now the light stays on 12 hrs. a day, the 3 rd week the light and fan stay on 24 hrs. a day. After 3 weeks they are dry enough to return with no warping happening afterwards.

I don't do this very often anymore, because I get so far ahead with rough turned bowls, I always have something that's been sitting around for year or so.

There was an article in Woodturning Design that showed how to do this with an old refrigerator. I didn't have one so I made mine out of plywood, it's about 4ft by 6 ft. I rarely have a bowl crack this way, but of course if you leave the pith in the wood nothing will stop if from cracking and some woods like apple might crack now and then, although the ones I've done so far haven't.

[John King]

Checkout "Drying Wood to Get Round Bowls" by Marty Kaminsky at http://www.gulfcoastwoodturners.org/RESOURCES/Articles.html. - John

[Anthony Diodati]

Wow, Thanks guys, a lot to read and think about.
I just got this wood here, for $75.00, said to be klin dried, but there was some checking, and some pith.
All in all, it's pretty nice, and considering what wood craft and rockler sells there blanks for, I don't think I did bad.
It's all about 3 1/4" thick, and one is 3.75 thick.

I was sealing the ends on this walnut, a few of them have some pith, the one I didn't think it ran the whole length, ~16", so I cross cut it half way.
I was right, so I only had to cut out about 1" of pith on that one, The full length. (of one of the cross cut pieces)
It only (the pith) went about 2" it, must have been slabbed out at an angle some how.
But there is some pretty grain in there.
As long as it "behaves it self". I got it all sealed up, some of the pieces that were close to the pith with the nice grain, I lightly sealed all over, and sealed the end grain with 2 coats.
But the piece I cross cut to ~8" you can just feel it is still somewhat wet.
So I have to treat this wood as only somewhat dry.
I am gonna just try to get him to just sell it to me green next time if I can.
He was worried about it blowing up, if I dried it too fast.
This guy did this for a regular job all his life, now he does it on the side, so he should know what he is talking about.

The cherry bowl from the log I found down on Route Ohio 7 on the way home from getting the walnut, I turned to completion, as opposed to rough turning, finish turning later, about 1/4" or less wall and bottom thickness, but sitting over night on the lathe with the heat left on, it stayed nice and round. The log was pretty green, as it had not even started to crack on the end grain/pith area.
Lots to learn.
I always understood walnut was one of the more stable, well behaved woods.
Also got this magnetic tool holder at rockler, Could be a little stronger, but it holds the flat tools pretty well.

[Thom Sturgill]

Also got this magnetic tool holder at rockler, Could be a little stronger, but it holds the flat tools pretty well.

Might want to re-think that tool holder. It can magnetize the tools and that can hurt how they respond to the tool rest and it affects the crystalline structure of the steel. the hardening/tempering process is done to create a specific crystalline structure and magnetizing the metal can't help that either...

[Anthony Diodati]

Might want to re-think that tool holder. It can magnetize the tools and that can hurt how they respond to the tool rest and it affects the crystalline structure of the steel. the hardening/tempering process is done to create a specific crystalline structure and magnetizing the metal can't help that either...
That sucks, OK thanks, I'll come up with something different.