Mini indoor "kiln"

[Graeme48]

If you're needing or wanting to build a small cabinet type of thing to try and dry wood you're better off looking for an anti condensation cabinet heater rather than using light bulbs. Unlike a bulb cabinet heaters are robust and last for years with continuous use. Farnell is one supplier and their power ranges from about 20W upwards. Slainte.

Apologies for hijacking this thread slightly but here goes. Last year, I built a small kiln from a freezer to dry wood blanks for woodturning. This uses a 40w incandescent bulb for heating & bathroom fan for cooling, both controlled by a thermostatic temperature controller. Being somewhat uninformed on these matters, I had never heard of an anti-condensation cabinet heater, but it sounds a much better option - can anyone suggest what power might be best? Freezer cabinet is 6ft high x 2ft x 2ft external dimensions and I am looking to run it around 24 degrees. Thanks

 

[Inspector]

Some woodturners make a kiln from old refrigerators by having the freon removed, making a few holes in the bottom and a few more at the top, then putting a lightbulb (old style incandescent) or a little heater like transatlantic suggested in the bottom. The warmth rises, drying the wood and setting up a little convection drawing dry air through the bottom holes and moist air out the top. You have control over the amount of heat inside if you put in a thermocouple and block off the air holes if needed. There are lots of youboob videos showing how to make them.

If you want to dry wood faster (a week give or take) with minimal degradation a Vacuum kiln is the way to go. There is a little book about it showing how by Joshua Salesin. Amazon.ca

Pete

Looks like Graeme beat me to the fridge/freezer suggestion.

 

[Sgian Dubh]

Something like this RS PRO Enclosure Heater, 20W, 230V ac, 70mm x 65mm x 67mm | RS Components ?
So would this just be an empty box with the heater hanging from the top?

Exactly that type of style. I have one in each of my tool cabinets, and my tools never get rusty because of their presence. I can't recall the wattage offhand, but they're probably 20 or 30 watts. I have them mounted in the base of the cabinets so that the gridded cover faces left and right and upwards. They're robust with a coil under the cover mounted to the base plate, and can take a whacking or dozen, as I've proved to myself, and they must have been in my tool cabinets for ten years or more running continuously. That beats having to replace light bulbs on a regular basis in my book.

I'd need to go through my business accounts to find out when I purchased them, but I hope you don't mind that that's more effort than I'm willing to put in, ha, ha. Slainte.

 

[Sgian Dubh]

can anyone suggest what power might be best? Freezer cabinet is 6ft high x 2ft x 2ft external dimensions and I am looking to run it around 24 degrees.

Some guidance here, I think. Second paragraph down in the link suggests, "10 watts per square metre of cubicle surface area may be used" but bear in mind that's only to prevent condensation. I'm not sure how you might work out what heater you'd need to give a consistent 24ºC.

 

[Paul Hannaby]

You would put the heater at the bottom to encourage convection

 

[Graeme48]

Some guidance here, I think. Second paragraph down in the link suggests, "10 watts per square metre of cubicle surface area may be used" but bear in mind that's only to prevent condensation. I'm not sure how you might work out what heater you'd need to give a consistent 24ºC.

Thanks for that. Being a well insulated freezer cabinet (at least before I cut holes in it), it holds temperature fairly well but on the basis "10 watts..." quoted above, I am guessing that 40W should be the minimum. If temperature should go above the required 24, the thermostat will shut it off anyway.

 

[Sgian Dubh]

I am guessing that 40W should be the minimum. If temperature should go above the required 24, the thermostat will shut it off anyway.

I suspect that as well as a thermostat it would be a good idea to incorporate a small fan to encourage airflow, a fan probably similar to the ones found in desktop computers might be about right, but some research on your part would be a good idea. It's airflow that takes away moisture as wood dries, particularly in the early stages when wood is at or above FSP (green). Also, the wood at the intake side of the airflow is always going to dry quicker than the wood at the outflow end. In professional kilns the airflow is reversed on a regular basis, e.g., every four hours to even out the drying process. In truth, at the early stages of drying wood, from green down to 20% MC, the primary means of getting moisture away from the drying wood's surface is airflow, although controlled warmth is also important. It's only when wood reaches a moisture content of 20% that relative humidity becomes the primary cause of further drying or moisture loss. Slainte.

 

[Adam W.]

Can you not just stick it all outside under cover, in the wind ?

 

[Sgian Dubh]

Can you not just stick it all outside under cover, in the wind ?

Adam, surely you realise that's far too simple and lacks necessary technological input needing money spent on it - jings, crivens, help ma boab. Plus, he's got an old freezer that's almost found a new purpose, ha, ha. Slainte.