Small kiln ideas

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Small kiln ideas

Postby aaronsterritt » Fri Jun 27, 2014 12:25 pm

Hi all

I'm looking at building a small kiln to dry some green chunky Oak stool legs ( about 2 1/2" thick at the widest point). My plan in to rough out a round tenon on all of them first, then put them in the kiln. I will be jointing them onto kiln dried seats so i want to make sure the tenons are bone dry and not going to shrink. I've tried putting them in the oven, it does work to an extent i.e. the tenon seem to dry out enough but at the cost of the thicker parts of the legs cracking - it's too quick!

I've got a dehumidifier already that i think will do the job. My idea is to build a 2m tall, 1m wide box, insulate it with kingspan, put in a shelf up top for the dehumidifier, stack the wood at the bottom with a halogen bulb. Has anyone built something similar? One thing i'm defiantly not sure on is the halogen bulb? How powerful would this need to be?

Any help much appreciated.

Thanks

Aaron
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Re: Small kiln ideas

Postby Steve Martin » Sat Jun 28, 2014 4:19 am

Don't know how available they are on your side of the big pond but I used an old/broken dishwasher, under cabinet model. Moved it to workshop, Put a portable light socket (like a mechanic might use in the engine compartment of a vehicle) in the bottom with a 40 watt bulb, higher wattage makes it too hot. Put chair legs on top rack of dryer, turn on light, close door, check in 2 days. If one or more legs seem to be drying faster than the others, shift them around. I dried a maple bowl (10" W x 4" H x 1" thick) in about 2 weeks with no cracks. Have done several spoons and had small cracks actually close up while drying.

The dishwasher is constructed to deal with wet heat, so it is vented already. I didn't care about a cabinet around it in the workshop, so I just cut a piece of plywood for a top so I also got another flat surface, on which to put something else, such as a sharpening station. Good Luck!
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Re: Small kiln ideas

Postby gavin » Sun Jun 29, 2014 1:36 pm

Put car in sun with window slightly open. Put work in shade within the car.
Weigh periodically. You'll soon know when you get to EMC i.e. equilibrium moisture content.
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Re: Small kiln ideas

Postby aaronsterritt » Sun Jun 29, 2014 5:08 pm

Thanks Steve

That's loads of help, i managed to find an old chest freezer. I think this will do the job. Quite a bit bigger, so was thinking a couple of bulbs. maybe 60w? Was also thinking of putting a dehumidifier in as well after a week drying or so. Unfortunalty the sun doesn't shine that much here in scotland Gavin! :(
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Re: Small kiln ideas

Postby SeanHellman » Sun Jun 29, 2014 10:47 pm

I think this is a bit of a big ask, oak is a slow dryer. I would boil or steam them for an hour or more, pull out of the heat and hang up to dry. Steamed wood dries a lot faster that stuff put into a kiln. There is another trick to make sure the tenons are dry and that is to put them in a few inches of sand which is heated on a cooker ring. Be careful it is easy to burn the wood, again you are looking at hours like this.
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Re: Small kiln ideas

Postby AlexanderTheLate » Mon Jun 30, 2014 12:02 am

Wouldn't it be easier to knock up a sort of rack and have a fan blow through them for a few days? I doubt a light bulb is worth the bother.
I fear the day that technology will surpass our human interaction. The world will have a generation of idiots.- Unknown.
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Re: Small kiln ideas

Postby Steve Martin » Mon Jun 30, 2014 2:17 am

I agree the freezer would probably work but you may want to put a couple of holes in the top to insure the moisture can escape. I would try one 60 watt (incandescent) bulb. Then add another if it seems to be going too slow, the insulation is pretty thick and if the rubber seals are good, it should hold the heat in very effectively. Wire racks to hold the piece(s) off the floor will improve circulation around the piece(s). Florescent bulbs don't make the same heat levels, in my experience. I think Gavin's car idea would also work, even in cloudy weather. Try a thermometer in a car with the windows up. Good Luck!
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Re: Small kiln ideas

Postby aaronsterritt » Mon Jun 30, 2014 10:37 pm

Thanks Guy's

So what i'm thinking of trying is a 60w bulb (got another one wired in if not enough heat). A small fan circulating the air 5mins every hour. Thinking of putting a dish of water in for the first few days, get the moisture content right up. Then either put a dehumidifier in or have holes in the top (would be sealed over for the first few days) to get rid of the moisture. Plan is to have a thermostat to control the light, what do you think would be the right temp to try and maintain? 90 F or hotter?

Thanks again
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Re: Small kiln ideas

Postby AlexanderTheLate » Tue Jul 01, 2014 1:46 am

Thinking of putting a dish of water in for the first few days, get the moisture content right up.


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Re: Small kiln ideas

Postby Steve Martin » Tue Jul 01, 2014 5:51 am

I don't understand about putting in bowl of water. Neither do I have any idea what temperature to shoot for. When drying spoons or small bowls in the microwave I heat them long enough not make steam come out of the piece, BUT I watch it carefully because I have set 2 on fire before I realized how dry they were. The dishwasher/freezer dryer should not make steam but should give the water time to work it's way out of the center of the piece(s). A SWAG would be 90 to 100 Degree Fahrenheit.



(SWAG is Sophisticated Wild Ass Guess.) :-)
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Re: Small kiln ideas

Postby gavin » Tue Jul 01, 2014 9:51 pm

aaronsterritt wrote:Thanks Steve

Unfortunalty the sun doesn't shine that much here in scotland Gavin! :(


O yes it does where I live in DG5 4BE in Scotland. Give the car method a shot if you have car. Do use electronic scales if you have them.

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