Kiln Advice Please.

[Johnny65]

Hi Guys,

I'm in the process of making a kiln from an old freezer, any advice would be appreciated. I mainly make bowls, so the part turned bowls could be as big as 18 inch diameter.

Got the 1.5 metre high freezer, hole saw holes drilled in the sides at the bottom and one in the top.

Biggest dilemma is how to gently heat it, modern light bulbs don't emit much heat, what I have got, is a greenhouse heater in my greenhouse that I no longer use.
It has got a low and high heat setting and I was thinking of using this.
Any thoughts or better ideas would be appreciated.

Cheers John.

 

[Cabinetman]

I was going to suggest a tubular heater but that’s probably what you have from your greenhouse, you definitely need a thermostat on it if it hasn’t got one, or you could fit one inline to break the power to the heater – very easy to do. I think you’re problem is going to be not drying it out too quickly. Different situation I have a desiccant dehumidifier in a large walk in cupboard for my firewood and it splits and cracks beautifully! Ian

 

[Johnny65]

I was going to suggest a tubular heater but that’s probably what you have from your greenhouse, you definitely need a thermostat on it if it hasn’t got one, or you could fit one inline to break the power to the heater – very easy to do. I think you’re problem is going to be not drying it out too quickly. Different situation I have a desiccant dehumidifier in a large walk in cupboard for my firewood and it splits and cracks beautifully! Ian

I'm 99% sure it has got a thermostat built in, I've also got a timer plug and I could set it for example, to 4 hours on, 4 hours off, bit of experimentation required I think.

 

[peterw3035]

Interesting thread, I'm planning to use our old freezer once it's empty as part of my workshop rebuild. I've read some people just use a light bulb?

 

[Old.bodger]

Yes tubular heaters, approx 60watts per foot.

 

[Popey]

I use a similar setup for home brewing. i have a fridge with a greenhouse heater in the bottom. The temperature is controlled with an Inkbird controller which has two switched power outlets and a temperature sensor, one to switch the fridge on/off and the other to control the heater. You just plug it in, set the temperature on the controller and leave it to do it’s stuff.
Hope this helps!

 

[julianf]

If you just heat a sealed freezer with some wood in it, you will end up with high humidity and and then the drying will grind to a halt.

I don't know how quick this will happen, but, ultimately, without opening the freezer, the moisture will have nowhere to go, and it will occur.


You can get humidity probes and Arduino stuff amazingly cheaply now. Of course, the ultimate would be to have fans and heaters controlled so as to allow programming of environment.

As for heaters - how involved do you want to get, and where is the nearest central heating pipework?

 

[Johnny65]

Thanks for the replies, I think some of you are missing the theory involved in this, have a look at this short YouTube video.

 

[Cabinetman]

Yes you definitely need a thermostat, that was very basic what he did, also don’t forget to drill a hole big enough for a moulded plug to go through, you can always keep the bit you cut out and add a small hole on the edge for the wires should you want to block the hole again. A small fan to circulate the air would be beneficial as well. You can buy some very small Dehumidifiers. Ian

 

[Johnny65]

Right, all set up and running, set it half way between max and min on the temperature, 3 hours on and 3 hours off.
I've weighed one piece and the water content was 26%, not looking now for a few days.

 

[Cabinetman]

I think at this point on the learning curve you ought to have set time each day and remeasure, it would be a shame to lose those blanks. What moisture content are you wanting to get to? Ian

 

[Johnny65]

I

I think at this point on the learning curve you ought to have set time each day and remeasure, it would be a shame to lose those blanks. What moisture content are you wanting to get to? Ian

I think I'll have a look on Sunday, I'm aiming for 12 to 15% ? And weigh it again. The one I've weighed is mulberry, second row from bottom on the right.

 

[Johnny65]

Couldn't resist it, weighed my test subject piece this morning, initially it was 2246 grams, in 20 hours its lost 15 grams, no cracks, so to me that is a nice steady weight loss, not too quick, pieces only just felt warm.

 

[gregmcateer]

Please keep us updated, Johnny - I for one am interested to see how you get on

 

[Johnny65]

Been going for 6 weeks now, one disaster with a piece of rough turned cherry, it cracked to hell.
Heating wise I've settled for the lowest heat setting, on for an hour and off for 2 hours, so far so good.

 

[gregmcateer]

So is it literally a fridge or freezer body, holes drilled in specific (or random) places, a low wattage heater and a fan?

 

[Johnny65]

So is it literally a fridge or freezer body, holes drilled in specific (or random) places, a low wattage heater and a fan?

Look at the photo 2 April

 

[gregmcateer]

Thanks. So no other gubbins out of view?

 

[Johnny65]

No

 

[Owd Jockey]

I built ex-Freezer Kiln a few years ago. I control the temperature by the use of incandescent light bulbs. I use 40w/60w and 100w bulbs which are still available out there. The 40w gives a very gentle heat while 100w is quite fierce. I have never needed a fan as the hot air circulates very well and exiting the exhaust (which can be damped) in the freezer roof.