I have an insulated 14x14' building that I'm converting into a kiln to dry my bowls. I have a heater and dehumidifier. Does anyone have a recommendation fot the temperature and humidity? Thanks
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Kiln Drying
- Thread starter Paul M. Kaplowitz
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i believe you need a "lot" of bowls, start it out at low temp, after say 12 hours ?, increase the temp/humidy for another time slot, then increase the temp/humidy again.....
different woods will react differently, maple seems to be a good wood to use in kilm, while cherry i had a very low success rate
or start doing hf, turn green to finish, bag
enjoy, that building would hold a lot of turnings
different woods will react differently, maple seems to be a good wood to use in kilm, while cherry i had a very low success rate
or start doing hf, turn green to finish, bag
enjoy, that building would hold a lot of turnings
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According to what I gathered from a Trent Bosch class from several years ago, start off with a warm temperature, you don't need heaters just a few light bulbs and keep the humidity high. I think that your room is actually too big because you will need to add lots of moisture to raise the humidity so that the bowls don't dry out. Very gradually over the next several months, the humidity of the chamber can be very slowly lowered. It is important to have several fans going to keep air moving or else mold is likely to grow on the wood.
A basic point here is that the drying process needs to start at the same time for all bowls and they will all be finished drying at the same time. This method is not suitable for continuously adding and removing turnings.
The most important point about using a humidity controlled chamber is that it does not speed up the drying process -- in fact it may extend it. The purpose is to reduce the percentage of cracked bowls by having a controlled environment for very gradually lowering the moisture content.
A basic point here is that the drying process needs to start at the same time for all bowls and they will all be finished drying at the same time. This method is not suitable for continuously adding and removing turnings.
The most important point about using a humidity controlled chamber is that it does not speed up the drying process -- in fact it may extend it. The purpose is to reduce the percentage of cracked bowls by having a controlled environment for very gradually lowering the moisture content.
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Make some 4x4 closets in the space. That way you can follow good practice and batch your blanks. This assumes you're trying to force drying. Now you need a way to read RH and a way to control it in your kiln(s). SOP for timber is to start with warm air, because warm air can hold more moisture than cooler air. Allows one change of air to carry more away. The kiln schedule steps down RH over time until it's maintained in the 45% range for 8%MC at a basic 20C. Our lumber at college was maintained in such conditions so we knew where we were starting.
Not sure how much time you'll cut off of the drying process, which takes two months max for ~1" thickness on our northern hardwoods. So if you have three closets, each large enough to hold a month's worth of final turnings, you final turn one and refill with fresh while the other two cure with just a bit of flowing air and humidity care.
Just as a thought. I have gently pushed 1" stock to about 24 days from dead green. If I turn to 3/4, I can get the same with no push. I don't make broad bottomed turnings if I'm going to push, but I don't like the looks of them, so no great loss.
Almost forgot. Hit the fpl site with a "kiln drying" search for all kinds of information to temper the seat-of-the-pants advice you get in forums. Like this, for instance. http://www.fpl.fs.fed.us/documnts/fplrp/fplrp548.pdf
Keep good records of what you did, in case you need to modify.
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Several articles at the link on building small kilns and the schedule for using them. One persons schedule does it all in just three weeks.
http://www.woodturningonline.com/Turning/Turning_articles.php?catid=30
http://www.woodturningonline.com/Turning/Turning_articles.php?catid=30
Paul, I did a review of Glenn Lucas' video "Bowl Turning Techniques" for the current issue of the American Woodturner. In this video, Glenn describes his process for kiln drying green bowls in some detail. His are ready for final turning in eight weeks.
Dennis
Dennis
Paul, unless you can fill that room you are wasting your time and money. My suggestion is to get an old fridge being tossed out and gut it and use light bulbs to power the thing. Drill a few half inch holes in the top and bottom. Start out with a 40 watt bulb in the bottom. Get a moisture meter. You can either do the whole load in a few weeks by slowly raising bulb wattage or leave the 40 and rotate bowls from the top to the bottom and take them out when they get down to around 6%. You will have the rest of your shed for storage. Your 1st rack can be right above the bulb. Bowls will need to be waxed on the outside. You need no fan. A convection current is produced that goes 24-7. You only need a very small amount of room between work. Bowls can put into others as long as air can get into the inside of the bowl.
That said, a guy here took a building, put a dehumidifier in it with a couple fans and stacked tons of slabbed wood with stickers for air. 2 to 14 inch thick timber. No heater just whatever the temp was. He made a drain to the outside for water runoff. Funny, he air dried his roughed bowls on racks high up in the shop. Worked for him as it got hot near the ceiling. I checked it out a month into the drying and there was an almost small run of water coming from the drain. The building being closed up was very warm and humid inside. I think he ran that for a year. He stopped it when almost no water came from the drain. His son said the real thick slabs were still pretty damp in the center. But he said he would not do it again in that large of quanity as they were a small shop and did not need that kind of forced drying.
That said, a guy here took a building, put a dehumidifier in it with a couple fans and stacked tons of slabbed wood with stickers for air. 2 to 14 inch thick timber. No heater just whatever the temp was. He made a drain to the outside for water runoff. Funny, he air dried his roughed bowls on racks high up in the shop. Worked for him as it got hot near the ceiling. I checked it out a month into the drying and there was an almost small run of water coming from the drain. The building being closed up was very warm and humid inside. I think he ran that for a year. He stopped it when almost no water came from the drain. His son said the real thick slabs were still pretty damp in the center. But he said he would not do it again in that large of quanity as they were a small shop and did not need that kind of forced drying.
With that in mind, I might not live long enough to turn wood!😀
Drying Building
The reason I'm trying the building as a drying room is because it was taking 6-8 months with the bowls in the unheated garage. I have about 250 bowls drying at any time. I thank everyone for their help and I'll let you know how it turns out.
The reason I'm trying the building as a drying room is because it was taking 6-8 months with the bowls in the unheated garage. I have about 250 bowls drying at any time. I thank everyone for their help and I'll let you know how it turns out.
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Six or eight months? Wow. Are you coating them? My attached garage does a bit more than half that even in winter, because I keep them up against a house wall. Good place to hang the onions, too. Though the whites still go soft in three months, the Stuttgarter brown will make 5, and the shallot I sliced and put on last night's baked salmon was a turgid as the day it was pulled.
Blanks are up off the floor, of course. http://i35.photobucket.com/albums/d160/GoodOnesGone/Bowling.jpg No coating.
Blanks are up off the floor, of course. http://i35.photobucket.com/albums/d160/GoodOnesGone/Bowling.jpg No coating.
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The juried "art" shows have the kind of attendance that likes decorative work, as opposed to "craft" shows. If you've not gone to one of them, give it a try. Not all years are good for all shows, but sometimes you regret signing up for a third show as you pack from the second ... all the way to the bank.
Hey Paul,,, I have a 10 x 10 room built in my shop that I use for drying and storage of burl blocks. I use it more for storage than drying, but the two kinda go together.. I have a mixture of waxed and unwaxed blocks in there,, I always try to keep my humidity between 30 and 50 %.. below thirty you are looking at cracking, above 50 for extended amounts of time your looking at mold.. This is no kiln,, but the drying process seems to pretty stabile I believe do to the humidity factor. In the winter months (it gets really cold here) I use a heater to keep the temperature right around 65 degrees all winter, summer months I am limited to mother nature as far as temperature but I do use a dehumidifier in the summer do to higher humidity factors.. Hope this helped a little.....