Thread: Wood Drying, not in the microwave

I have seen small kilns that look just like a small plastic igloo type hot house.
Just a few hoops covered in thick clear PVC with shelves inside.
A few warm weeks and the claim is they work well.
I have never tried it but having had hothouses before I know they maintain a steady temperature overnight.

9fingers - Over the years, I've often come into a pile of green wood - windfalls, irresistible bargains, clubbing in with other w'workers to buy a few cubes of something or other to share out. Every time, I was busting to get stuck into it, and make the grand pieces it was destined to become. But having no space/time to get into kilns, I just stacked it and let nature take its course. Without exception, by the time I got around to using the wood, it was well and truly ready - you could have allowed 5mm per year drying rate, and it would still have been OK!! In fact, the one time I did go to great lengths (and some expense!) to find a kiln prepared to custom-dry the Black Walnut tree I'd stumbled on at a little pallet-mill, I still didn't make anything serious from it until long after the air-drying process would have taken care of it.

Of course, I'm a weekend wood-worrier, and perhaps there are some woodies out there, or professionals, who are better organised, but if you are a part timer, situated any place where you can get hold of green lumber, and have space to store a few cubic metres, you will quickly find your capacity to acquire and store raw material vastly outruns your ability to craft it into fine furniture (or even rough furniture, I reckon ). There are a lot of very large piles of wood around various backyards that support my argument...

So why do so many of us go after our own wood? I've got enough gear to take advantage of 'windfalls', but find I am less and less inclined to chase it, mostly because milling, carting and stacking is such a time-consuming business. On reflection, it is much more economical to go and buy what you want as and when you need it. The only reason I can think so many folk do it is because it's a bit like gold-prospecting - it gets in your blood, and you keep imagining the treasure that's going to be inside the next Camphor-laurel you bust open. Most often it's another nail! :mad:

So beware - collecting green wood is as bad as getting on the slippery slope of plane-collecting!

PS - There are lots of designs for small kilns - solar kilns can work even in Michigan, I believe..........

Avagooday,

Yup.. Solar kilns are an option.

Relatively cheap, especially if you have plenty of wood to build it and will work in practically any climate. (just a lot slower in winter)
Should take your drying time from years to months anyway.

Have a look at http://www.woodweb.com/knowledge_bas...to_Lumber.html for some ideas
And http://www.woodweb.com/knowledge_bas...olar_kiln.html has photos of one completed.

And I agree with IanW on the addictive bit... 'wonder what the grain is like inside that log??' And the 2 or 3 year stash of timber And the hard work..

Cheers

Ian

Originally Posted by Ianab

And I agree with IanW on the addictive bit... 'wonder what the grain is like inside that log??' And the 2 or 3 year stash of timber And the hard work..
Ian

Wot, Ian - who said 2 or 3 year stash? I've got mine down a bit, by being particularly strong-willed (and having limited space ), but I could probably coast, at present rate of useage, for a good 10 years....
However, I'm due to be culled for age from the day job, in a few more years, so have to start collecting in earnest, now!!

AWR issue 32 Neil Erasmus describes a small kiln he has for veneers and smaller stock

It starts as a box made from 25mm chipboard 2400 x 1200 x 1200, with a pair of 1200 x 1200 doors to swing open to load and un-load.

Inside is an oil filled 2400 watt themostacically controled heater. Its fitted with a hole exposed at the rear to expose the heaters controlls. (all sealed of course)

An inexpensive digital thermometer`s probe was inserted through a hole in the top.

A long secondry box inside at the bottom rear containes 4 fans to concerntrait air flow within a smaller volume.

An of the shelf 15 litre dehumidifier which he keeps on the minimun humidity level.

Their are great photos to get a better idea and it dose look good for those of us wanting to dry smaller sections... Check it out

Cindy Drozda’s drying kiln

To dry my rough-turned vessels, and blanks for smaller projects, I have made a drying kiln out of a recycled chest freezer. The freon has been removed and the chest freezer is standing up on end with a couple of 2x4s underneath to space it off the ground to allow the door to work properly. The material to be dried is placed on "flow through" shelves made from salvaged oven racks.

The freezer has holes in the sides at top and bottom, and a couple of 60 watt bulbs inside at the bottom. Convective airflow is the key, and no fan is necessary. The bulbs heat the air, the hot air rises, and air is drawn in through the holes in the bottom and flows out through the holes in the top. The relationship between the number of holes (airflow volume) and size/number of light bulbs (watts of heat) can be adjusted to give a temperature inside the kiln of about 85 degrees F. This "kiln" dries wood in about 1/3 of the time that it would take out in the shop at the same air temp because of the dry-air-flow.

I have had good success drying roughed out vessels, bowls, and boxes. And I have success, also, with drying solid blanks up to about 3” thick for pens and small projects. The outside of rough vessels, and all surfaces of solid blanks, is coated with “Anchorseal” type end grain sealer. There is sometimes some cracking of solid blanks, depending on species, natural features, and what the moisture content of the blank was when I put it in the kiln. If a species is known to be “crack prone”, and the material is very wet, I will sometimes put the waxed blanks in a cardboard box for a couple of months first. Usually, I prefer the “cracked look” and don’t mind some cracking ...
The first drying kiln that I made was blue construction foam held together with PL400 adhesive. The foam was easy to drill for the vent holes, and I made shelves by drilling holes through the sides of the box and running ¾” x ¾” oak pieces through the holes. The door was just a slab of foam held in place with a bicycle inner tube around the whole box. Plywood sheathing was not necessary; this kiln lasted for years untill I wanted a bigger one. The foam box was the easiest way by far to make a drying kiln. The freezer was a lot more work to drill and mount shelves.

When I first started using the drying kiln, I did some tests with a scale to see how quickly the blanks would dry in the kiln. A ¾” thick x 6” diameter, open bowl blank, of Honey Locust, with sealer on the endgrain was weighed every day. It lost all the weight it was going to in about 6 days. After being in the shop for another couple of days, the bowl gained back some weight. From this experiment, I am guessing that the dry air inside the kiln is evaproating out the cellular moisture from the wood. Then when the wood is exposed to the air in the shop it is absorbing atmospheric moisture. Remember, I live in Colorado – a very dry climate. And most of what I dry is roughed out vessels and small project blanks of burl material. Other parts of the country (or the world) might have different results.

The difficulty is in knowing when the blanks are completely dry. A “pin type” moisture meter needs to have a freshly cut surface, and a “pinless” meter needs a flat surface. Weighing each blank every day is incredibly time consuming, and requires a good quality (expensive) scale. I don’t have a high-tech solution to this problem. My approach is to gauge the dryness of vessel blanks by how much they have distorted, or by past experience with that species, or “just give it plenty of time”. For small project blanks, I will cut them square before drying (as opposed to rounding them off). Then after the blank has been in the kiln for awhile, I will cut off one corner and check the moisture content with a meter. A square blank gives me 4 chances to check.




I bought a fridge for $7.50 (upright) and made one of these and it seems to be good

That's much like my drying cabinet; an old clothes-drying cabinet with a light-bulb installed at the bottom. It works well for thinner materials, I doubt they'd make significant difference on the larger chunks put aside until they're rough turned for bowl-blanks.

For short boards it also works fairly effectively. We're not talking days here, it's weeks, but that's better than years, right? No good for anything of really decent length.

It's not a kiln, but I guess it's the first tottering step towards one.

I have a standard tin garden shed that works real well as a kiln. Even in winter the closed door temp stays above 30C most of the day in summer it can get up to 45C.
I started using it for fire wood then I realised it dried the wood real well.
Just make sure you get a dark colour and site it in the sun.
I recon it would go better with some electronics and a fan or two. But it works prety well so far.
cheers

Originally Posted by soundman

I started using it for fire wood then I realised it dried the wood real well.

Just imagine SWMBO not knowing the difference:eek:

For anyone needing a small "kiln" for drying, check this thing on ebay (Clayton, Vic)

No affiliation, etc

http://tinyurl.com/c4o5x

Greg

Originally Posted by gregoryq

For anyone needing a small "kiln" for drying, check this thing on ebay (Clayton, Vic)

No affiliation, etc

http://tinyurl.com/c4o5x

Greg

Those things are designed to dry soils and the like down to 0% moisture overnight. They suck moisture faster than a camel at the first bore well on the far side of the Simpson desert.

I reckon that using one to dry timber would be a real challenge, just in keeping sufficient moisture around to prevent the stuff collapsing like a souffle in an earthquake.

You could try cycling the fan on and off with a steamer of some sort to humidify it, perhaps. Maybe Glock might have some thoughts?

Originally Posted by Exador

Maybe Glock might have some thoughts?

G'day.
Even for my own personal use, I'd still air dry.

This is the trouble with people trying to dry timber in equipment that was never meant to be used for it.
By the time you throw money at it to get to a workable unit. You would be better off spending the cash on a slip kiln or similar.

Hooroo.
Regards, Trevor.
Grafton

P.S. Craig, did you have a yarn to "Red"
G'day Bruce, when does the second head start to grow

There was a design for a dehumidification kiln in FWW a few years ago.

Originally Posted by glock40sw

G'day.
Even for my own personal use, I'd still air dry.

This is the trouble with people trying to dry timber in equipment that was never meant to be used for it.
By the time you throw money at it to get to a workable unit. You would be better off spending the cash on a slip kiln or similar.

Hooroo.
Regards, Trevor.
Grafton

P.S. Craig, did you have a yarn to "Red"
G'day Bruce, when does the second head start to grow

Thanks for the thoughts Trevor. I didn't get over to DPI last week, despite best intentions. Hopefully in the coming week. I'll make sure I say g'day for you.