Max practical thickness for conventional kiln?

[Dave Shepard]

What is the maximum thickness that can be reasonably dried in a conventional kiln, i.e. heat and vent, not DH? I may need to have a way to dry fairly thick pieces of wood for making workbench parts, and some may be up to 16/4 hardwood. I realize a vac would be better suited to this kind of work, and if a conventional is not practical, I will look into that as well. Thanks.


Dave

[Den Socling]

I consider a 'DH' kiln a conventional kiln because like a heat & vent kiln, they can only evaporate water off the surface. A vacuum kiln can actually evaporate water inside the wood. The depth of this evaporation depends on the porosity of the wood but the effect is to minimize moisture gradient. Naturally, if you are removing water from the surface only, it's very difficult to keep the surface from over-drying while you get water out 12 or 16/4.

The other limiting factor is time. When talking about drying from green (without long air-drying) anything over 4/4 can be too costly because the conventional kiln runs too long.

Some of our customers accumulate partial packs from over-runs or sizes that didn't meet orders. They won't give this wood away but, if I needed a few hundred or even a couple thousand thick pieces, I would look to them.

[Dave Shepard]

Thanks Den. I didn't realize that a DH was a conventional kiln, I only wanted to clarify that I was thinking of using heat and vent, not DH. I know of a very interesting peice of scrap that might make a great small vac kiln. It is a stainless steel pipe about one inch thick and four feet in diameter and at least eight feet long. It has ribs one inch thick and four inches tall welded around the outside and a lid that bolts on with about forty bolts. I have no idea what it was used for, but I don't think it will rust, implode, or explode any time soon. :D I also know where there is a new 3HP vacuum pump that could be had for not much. I won't need large volumes of wood, but cutting the drying time would be great. Does a vac kiln have less of a chance for degrade in the thicker stuff do to remove moisture all the way through the piece?


Dave

[logwalker]

I would think that the 3 hp vacuum pump would be much larger than needed. I am guessing you only need a 1/4 or 1/2 hp running continuously to do the job. I am no expert by any measure. Joe

[Kcwoodbutcher]

That vessel sounds as if it will work, if not it's worth a fortune in scrap if it's all stainless. Still it's only half the equation. You still need a means of getting heat to the wood by using blankets or heated water shelves, den would know more about that.