Tiny kiln ideas

[Ventryjr]

Has anyone built a small kiln.  Possibly from a chest freezer or something similar?  I don’t want to get into drying big wood. But I’d like to dry a few fancy cheese boards and small stuff like that.  Anyone have any pics or ideas for something like this?  Thanks in advance. 

[Larry]

Woodturners often dry wood in a old refrigerator with a light bulb or two in it for heat.  Pretty simple and never thought it worthy of taking a picture.

If your stuff is small enough in can be dried in a microwave.  I have one in the shop that has dried lots of small stuff plus heating up a cold cup of coffee.

More advanced are the shop build small vacuum kilns.  Many designs.

[doc henderson]

 

 
old blanket and fluids warmer from a hospital.  I got a second for free as I work in a hospital.  I gave it to a cardiologist friend @Cardiodoc
i planned a hot box that was to be lined by galvanized duct metal with corner joints, 2 x 4 x 10 feet, but the metal with labor cam to over a thousand bucks.



 

[Ianab]

A large box with a home dehumidifier will dry wood OK, especially if it's mostly air dried first. Just needs a bit of warmth and some way to get the moisture out, that's what the DH does. Otherwise you need to vent some moisture somehow, and that looses some of your heat as well. The DH produces some heat, blows the some air around, and removes the water water. If the wood is air dried it's hard to mess up even, if the kiln control isn't perfect. 

Only thing is it wont get hot enough to sterilise the wood, so you have to be careful about bugs. Spraying the green wood with borax solution might help. It's not particularly toxic to humans and it would plane off once the wood was machined. 

[Ventryjr]

@doc henderson    Any chance you wouldn’t mind sharing more of your design?  Like heating element and air circulation?  I have a full sheet metal shop so 16-26 gauge galvanized is easy for me.   


@larry with the refrigerator setup was there no air circulation ? Or did they add in some type of small fan?   

Thanks again! 

[K-Guy]

@Ventryjr 
Use aluminum not galvanized. The tannic acid will wear off the galvanized coating and rust it out.

[Ventryjr]

@Ventryjr
Use aluminum not galvanized. The tannic acid will wear off the galvanized coating and rust it out.

@k-guy 
I have a 4 ton roll of 24ga galvanized with a medical grade antimicrobial coating.  Do you think that would be a better option? 
I’m trying to work with the materials I have on hand. Thanks! 

[K-Guy]

No
Galvanization is just a coating and will wear off. 

[Nebraska]

Just a thought, you might be able to spray foam the interior to protect the metal it as well as insulate it.

[doc henderson]

so I bought a dryer element (cut off at 160°) and the plan was to put that in a duct (triangular roof part) and have a circ. fan for that.  poss. a variable thermostat, but mostly wanted it for a sterilizing hot box.  I do not want to ruin my blanket warmer with all the humidity and caustic chemicals.  I may price stainless. but the reason for the galvanized was I thought my heating and air guy whom I often help and vice versa, might get me a great deal at his work.  I got thrown to the wolves and worked up as a major for profit job.  they are high end, and do a lot of houses with sidewalk heat and floor heat ect.  I was thinking I would design it so the floor could be changes out, and poss. covered with alum roofing material.  planed to have a drain so the condensate would not condense and pool or have the water evaporate and concentrate the caustic stuff from the wood.  Or have it o the bottom had a drain, and or the ability to be replaced intermittently.
I will try to get more pics, but I think the "whole made at the high end heat and air shop" may be on hold.  too much going on now.

[doc henderson]

I was going to put duct insulation on the outside, but it is 1.25 a square foot for R4.  If you have the materials at cost and tools,  pick a size.  find a heat tolerant fan, and a dryer replacement heat element on amazon for 25 bucks with all the thermal switches and fuses.  and set it up.

[Larry]

with the refrigerator setup was there no air circulation ? Or did they add in some type of small fan?  

Muffin fan or just a couple of vent holes.

[Sod saw]

.


If you can find an older smallish incubator. . . One for hatching bird eggs. 

They are well insulated and have heaters built in.  Most chicken / duck / gamebird eggs are hatched at 98 to 99 to 100 degrees F.

Most incubators have vents built in, so the eggs can be kept as specific humidity thru their hatching cycles.  Sounds like the description for a kiln, doesn't it?

But you may have to add heater to sterilize your wood at higher heat cycle.

Our game bird farm had different size incubators from table top size to some that were large enough to hold a small car.

I bet that you could find one used on face book or Craigslist.

have fun with your projects.


.

[doc henderson]

I got an infant warmer and used it for eggs 26 years ago.  very heavy on a cart with wheels.  lots of safety stuff so you did not over heat a newborn or preemie.  I gave it away before we mover in 01.  check with local hospital, if you know someone in maintenance.  most hospitals have a ware house of old stuff they will sell when there is no need for parts, or to resurrect it.

[greensman]

you might try an easy bake oven approach.  several chairmakers i know of use a small insulated box with light bulbs as the heat source.  they are using these to do the final drying for legs, rungs and other small parts to get the mc from around 20 down to 10.  I built one that is a 3x2x2 plywood box with foamboard insulation stuck inside, two 100w light bulbs, a computer fan and two wire rack shelves.  the bulbs and computer are controlled by a thermostat that keeps the temp within a range I specify.  I have also seen some temporary kilns built for this purpose that used only foamboard for the structure.  

[LeeB]

Stock up on incandescent bulbs if you go this route. They are getting hard to find.

[Ventryjr]

I think I’m going to fab up a sheetmetal box and insulate the outside of it. I need to Figure out some sort of electric heating element and small fans.   Im thinking 2’x’x5’ long. I can handle basic time/temp controls easily with parts laying around. I don’t want to dive into humidity sensors/controls.   What’s a good target temp to hit 180-190* inside the box?   Thanks. 

[Walnut Beast]

Kill the bugs with heat. Known as
sterilization in the lumber trade, this involves
stacking the boards in a hot kiln. Your local kiln
operator may not welcome buggy wood into his
kiln, so you may have to build a heated enclosure
with fans for air movement.
To kill all of the bugs, the center of the wood must
heat to at least 133°F for 30 minutes. To achieve that
with 1" thick boards, the kiln would have to hold at
150-160° for about an hour, but two hours would
be safer. Wood thickness greatly affects heating
time: a 6×6 beam would require at least five hours
in such a kiln. How you stack the wood, air
circulation, and species also affect sterilization time,
so err on the wood being in the kiln longer than

[firefighter ontheside]

Perhaps your chest freezer idea and a DH that sits outside the chest, but is ducted in and out.  That will likely get the chest fairly warm.  As far as sanitizing, that will be a little more tricky.  In that small space any kind of radiant heat will likely be too close to the wood to be safe.  

[Larry]

What’s a good target temp to hit 180-190* inside the box?  

Too hot.  Start around 90 degrees and as you get experience with your wood you can slowly increase the temperature.

I dry leg tenons on my stools to a target of less than 4% in a sand pot.  These are already air dried and sometimes kiln dry legs.  My target temperature is no more than 180 degrees.  Above 180 the color of the wood can change or even char.  I'll often hit 0 MC after a day or two.

Sand pot heated by hot plate and oven thermometer shows temperature.