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Discussion in 'Woodturning Discussion Forum' started by John Turpin, Oct 30, 2017.
Yeah, but that's a Texas winter.
Yea I think some people use fans to circulate the air to keep mold down but that's on larger kilns for drying flat wood.
Sometimes it gets so cold that I need a long sleeve shirt and a hat on my bald head.
Okay. I've finally made some progress on my bowl kiln. The new studio is almost complete now and all that's left is small projects. So, I climbed back into the kiln/drying closet this week. The heating element went in. It's a pair of incandescent bulbs that are controlled by a thermostat. There's also a small USB fan that will keep air circulating while pulling a very small power load. There's a 3" air intake in the bottom and another 3" vent in the top with a sliding lid. The weather station in the photo shows temp and humidity for both the studio and the kiln. I still need to install some weather stripping around the bi-fold door.
It's not time-tested, but some early test are encouraging. Some short heating runs show the space slowly heating, but I've not yet figured out how warm it will get in there. (I'd love to reach 90 degrees if possible, but that cold winter cement floor will prevent that now.) I can play around with bulb wattage as needed. I don't really have a dehumidifier for it and don't have plans to add one. Hopefully the circulating air will help get some of that moisture out. I might also put a tub of marine desiccant in there and see what that does. It will be interesting to play with.
Wow, that is a nice kiln John. That should work great for your bowls and should help them dry much faster than my method of air drying in a bag of saw dust. Very nice indeed!
I read that if your cell phone/iPad/Andriod gets wet, you can bury it in rice. Wonder it that would work with wet wood???? After you turn the piece, you could make stir fry or rice pudding.
Don't forget to remove the turning before serving the pudding.
Isn't the pudding supposed to be IN the bowl?
The wood adds fiber.
John, you will find that when you put in a fresh load, most of the energy is absorbed in vaporizing the water in the wood. As it dries the temperature will rise. I start with a temperature at or just above ambient and slowly get up to about to 95-100F. I have some charts I have done of temperature vs weight loss and humidity for a presentation I did for a couple of clubs. Will try to remember to look for it tomorrow on my computer.
Here is the chart. It was over about three weeks I think. The data points were not necessarily equal in spacing but it shows what happens. Temperature is in Celcius. My kiln is detailed in an article at http://www.ghwg.ca/techniques/Mike_Brazeau_Simple_Drying Kiln.pdf
This is great data, Mike. Thanks. I'm amazed that the humidity would change that quickly. I'd expect it to take weeks for what you got in 10 days. That's encouraging.
It appears that the chart is is showing humidity of the air in the kiln which isn't moisture in the wood. Initially the wood contains a huge amount of free water. Free water leaves the wood very quickly, but the bound water can't leave until the free water in the same ΔV has evaporated. Also, I think that Mike is saying that he has ten data points over about three weeks and the numbers don't mean ten days and the sampling points weren't equally spaced.
Okay, great. That makes sense. I think I'll make a similar study to see what I find. I think my biggest problem is going to be heating that space. I've got about 70 ft3 and I'm not convinced that two bulbs can heat that adequately. I've got more options for heat, but am hoping that I can get up to temp without too much sophistication.
You might be surprised. If it is well insulated, you might be going for smaller bulbs.
I built a film drying cabinet using parts from a ceramic heater that worked quite well. I put it on a appropriate capacity dimmer control to be able to fine tune the heat level as well as keep the current draw down. It didnt have the thermostat hooked up because it has a pass through air path to get the moisture out quickly so I wanted a low continuous heat. Since you are regulating how fast the moisture escapes you will be using a thermostat with a controllable venting system. These heaters have dual elements for low/high ranges it can be set on low power to limit current draw and keep the temperature from fluctuating so much.
In my winter warfare training (Army), we were trained that a single candle would heat an igloo pretty well. I'd bet two incandescent lamps will heat this pretty quickly.
Eskimos heat an igloo with one seal oil or whale oil lamp.
Best thing to do John is to record and chart your various parameters on your first few loads. The humidity builds very quickly. You get to know what the percent loss by weight will be. An inexpensive digital kitchen scale that measure in grams makes it easy. Starfrit have a good one that is less than $20. I write the weight and date on a few pieces in the load to monitor. My kiln is about 15-16 cu ft and the air inlet and outlet is only three 1/2" holes. Depending on the wood it sometimes is totally wet inside. I found I baby sat the first few loads and after that put it in and checked it once a week or so for the duration. You may want to make up some things to reduce the interior volume for smaller loads as the high humidity in early stages is important. Not sure if they are still available but something like styrofoam coolers with their lids on would work.
That's a great suggestion, Mike. Thanks.