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Make your Own DIY Wood Drying Kiln 2023

Updated: Sep 2, 2023

So you've started this obsession known as Woodturning and after buying a Lathe and Hand Tools you are chomping at the bit to get turning. Problem is that you've very little wood to work with and what you get is expensive or hard to get. You then read an article or watch a video where someone tells you that you can cut and dry your own wood for a lot less money and time. Easy and no fuss! Well, it's not exactly that simple and you have a bit of work ahead of you before you can do this correctly.


Make your Own DIY Wood Drying Kiln

In this Post I will describe how I built and used my own DIY Kilns using retail glass front shop fridges. Any unit that is mostly insulated like Fridges, Dishwashers etc. will do but the bigger they are, the more wood you can dry at any one time. With my experience insights you may be able to set up your own system and dry wood for Woodturning faster and hopefully cheaper than buying off the shelves.


There are pictures in a Gallery below. Read the paragraphs first and then refer to the Gallery.


Disclaimer; You need to get expert advice on Electrics and Fire Safety!

This is only a guide of how I did this and not a definitive instructional manual. I am going to mention the safe way of doing things a lot because I want you to be safe while setting up and during operation. Get expert advice from a qualified Electrician before doing any of the wiring and make sure the kiln is properly earthed using Earth Wire and Earth Spike. Remember, you are dealing with Electricity and Water!


Fire Safety protocols should be set up (fire Extinguisher, Fire Blankets etc) so your house is not put in jeopardy. You are fully responsible for any and all consequences while using a kiln so take expert advice before going forward. No point in saving a few Euros or Dollars on wood and having to fork out thousands on home repairs!




Housing Requirements and Set Up

First of all, you need a sheltered area to house the kiln; preferably an outdoor shed or lean-to which doesn't leak and rain can't reach the unit. Remember, rain sometimes blows sideways, not just straight down!


Away from your house or valuable property is advisable too. An available power socket, preferably waterproof is also necessary, I don't recommend stringing extension leads together to reach the kiln as this is not safe practice. Have a Smoke Alarm, Fire Extinguisher and Fire Blanket in close proximity to the kiln at all times to be prepared for any eventuality no matter how remote you think the possibility is.


Air Holes

I started by drilling 4 x 1'' holes in the floor and the same on the left and right up near the inside top of the kiln. I could have limited this to 1 hole each side as 4 was total overkill. Most of the time the holes should be almost completely covered so that the warm air doesn't escape too quickly. A half inch hole would probably have been sufficient too and a control door much simpler to make. Too many holes and you might case harden the wood.


In the early weeks of use, the kiln should always look wet with droplets all over the glass and walls of the kiln. From the pictures below you can see that I made a plywood door with reflective insulating material to reduce heat loss through the glass. There are a variety of options to do this but I chose this way.


I also drilled holes in the floor so the warm air rising would pull in new fresh air which would in turn be warmed and circulated. There are many articles online that suggest drilling multiple large holes but I found that a few small ones do the job. You can always cover these holes if you find there is too much fresh air going in to the kiln. You can start off drilling one hole in the bottom and one each side and then experiment with each new load of wood. Drill more as required.


Metal Platform for trapping heat

This made sense to me after my first operation. I had Beech Bowls and some cracked because the heat from the bulb was too direct and severe. I got stainless steel platform trays made up with a downward lip on all 4 sides, in effect making an upside down receptacle. My thinking at the time, was that the tray would stop direct light from the bulb from reaching the wood and also allow heat to build up underneath the tray and dissipate more slowly.





PC Fan

At the time I was experimenting with wind and solar power and I had a couple of deep cycle marine batteries set up. A buddy of mine gave me 2 large PC fans which worked a treat using the batteries. The PC fan had a low CFM rate and gently pushed the air from below. Too fast and too direct air current can cause micro cracks, especially in bowls.


Important; Bowls and blanks should have their endgrain sealed with glue before going into the kiln to slow down moisture loss. Always use stickers to keep an air gap around the wood at all times.


Light for Heat

I rigged up a standard light pendant at the rear of the kiln about 6 inches above the floor. I chose this height so as not to melt the floor of the unit. The floor is light metal sheeting with plastic and insulation underneath.


I found so many articles about DIY kilns that say start a greenwood load with a 40 watt bulb and increase to 60 watt after a week, eventually getting up to 100 watts. I saw no need to change the bulb at all and the kiln reached temperatures of 20 degrees Celsius and above quite easily. If you want it to get hotter, close the air vents even further. You could add a 60 watt bulb to begin with but that may get too hot and will cost more to run. Using a 40 watt bulb and allowing extra drying time would be far better for the wood you are drying. Slower is nearly always better when it comes to drying wood!


Glass Front Cover

I realized during testing that the Glass Front was losing heat so I rigged up a cover of Marine Plywood with reflective insulating foil on the inside and a handle for easy removal. I also painted the lower end of the glass door to stop light reflecting back into the wood. This was a very effective and cheap solution.


Relative Humidity Monitor

You can buy battery RH devices and temperature monitors quite cheaply on eBay and though not 100% accurate should give you an indication of progress. During the first 2 weeks of operation there should be 100% Moisture Content in the kiln and it should drop slowly after that. Don't try and rush this by opening the vents. 1mm of air gap is probably more than enough on each side of the kiln. If the surface moisture on the fridge door starts to disappear too quickly you need to close the top air vents further or completely. Sometimes the moisture will escape through a closed hole without any need to open the vents, it depends on the material you use for the door. You will have to experiment yourself to find the best way.


Before Operating the Kiln

Before switching on for the first time I attached and Earth Cable to the metal frame close to the pendant and connected it to an Earth Spike driven into the ground close by. I asked an Electrician friend to double check everything was safe too. I didn't want to risk burning my workshop down so better to be safe than sorry. I have done plenty of wiring in my life but I always defer to a professional when there is any possible risk to life and property.





Operating the Kiln

When filling the kiln with wood, it is important to load the kiln with similar species and similar thicknesses. Don't put a 4 inch blank with a 2 inch blanks and expect them to dry over the same timeframe. Always use stickers to separate the wood and leave gaps all around for the air to circulate.


Container of water

Greenwood needs moisture in order to start drying so it's important to add a container of water so the heat can raise the humidity to 100% for at least the first week. In my case, I filled a Chinese takeaway container and left it dead centre in the bottom of the kiln. The greenwood will release moisture too so it shouldn't run out too quickly. You can add a bigger container if you wish. The heat from the bulb and the air movement from the fan will evaporate the container after the first week or so and the kiln walls and floor should be saturated at this point. As long as you don't open the vents too much during the initial stages the wood should dry correctly from the inside out.




As Simple as that but not really. In the first few pictures you will see a mix of Leland Cypress, Ash and Yew. This was back when I didn't know what I was doing and having just built the units I was itching to try them out. Experience has taught me that you can't dry hardwoods and softwoods together and you shouldn't dry different thicknesses together either. Keep 2 inch stock with 2 inch stock and dry 4 inch stock with 4 inch stock. Experimentation in the early stages of my business made things really exciting and most of the time I couldn't help but push forward.





Takeaway

Being able to source Hardwood yourself can be a much better alternative to purchasing from a store. It takes time to make these things and perfect your methods. You will probably be a Woodturner for many years whether in business or hobby level so you have time to get it right. Drying wood is a slow process, don't be fooled by any online articles promising you fast results. Wood doesn't work like that.


The best wood drying method I have seen is from Glenn Lucas who uses an Arrowsmith dehumidifier to dry bowl blanks in an insulated container in approximately 6 weeks. After the initial 100% wet week, cycles of 1 hr dehumidification and 3 hours off at around 35 degrees dries the wood slow enough for the moisture to leave the inside cells without the wood cracking. I have had good results from my DIY kilns but I was not very experienced at wood drying at the time. For small scale Woodturners, this type of kiln might suit you. If you like to experiment, this is a good one to try.


One Last Option

I saw another woodcrafter who set up a household electric dehumidifier inside a glass front fridge like I have above. A section of the floor and underneath was cut away to allow the dehumidifier to sit into the base. As long as the machine air vents are not blocked and the machine is allowed to vent its operating heat this could be an option. Again, you should only operate this while you are in the room or the fridge is located as mentioned above and doesn't pose a risk to life and property.


Whatever system you use, please do it safely and get someone qualified to double check your work.


I hope this has been helpful. Happy Drying!!!!!





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