Drying wood

[martin.pearson]

Anyone got any good methods for drying wood other than stacking it & waiting forever for it to dry lol
I buy most of my hardwoods as kiln-dried slices so I am OK with boarding it, I was given some yew about 3 years ago & it spent the first couple of years as logs before I cut it on the bandsaw into boards. I picked up some Laburnum logs recently & have started to board those so they dry quicker. It is mostly boards that I am looking at, I don't tend to do a lot of wood turning because of my arthritis.

I have experimented with microwave & oven drying but you are very limited on the length you can fit in either, I am now about to experiment with vacuum drying, I do some work with carbon fibre so have a pump I can use, going to try a couple of small pieces in a vacuum bag to see how that goes before spending money building a proper tank for the timber to go in.

 

[eribaMotters]

If it's for furniture I'd have thought that unless you can actually make or get access to a drying kiln, you are really down to that wait of one year per inch thickness plus an extra year. I'd then be looking at inside a dry garage or cool part of the house for another year.
I'm guessing for turning then somebody who knows a lot about these things would suggest turn it green oversize and then put it to one side and re-turn when dried out in ?? months.

Colin

 

[Inspector]

I haven't done it myself but do have this little book on the subject. It details what to do and how long the process takes, equipment, etc. When I lived on the west coast there was a wood supplier of local woods that had a commercially made one. He was able to dry a couple thousand board feet of wood from fresh cut to 8% moisture in about 2 weeks with no losses due to splitting etc. It had low temperature heating blankets between each layer of stickered wood. You'll likely end up somewhere between the two extremes. Only difficulty I see with a vacuum bag is circulating the air and having a low spot for the water to collect for draining. Since moving here where trees are not easy to get I have put it on the back burner.

Pete

 

[stuckinthemud]

I know of a bowyer who punched a hole in each side of an old microwave so he could microwave-dry bow staves

 

[Tris]

I recall an article in the woodturning magazine many years ago where someone (Alan Holtham possibly) had built a drying box based on a Sauno kiln. Logosol now sell that system but iirc the DIY one used a 2kw fan heater for heat input and an old computer fan as an extractor at the top.
There have been some built into an old chest freezer too, using a tubular heater, thermostat and fan but no idea how successful they are

 

[Owd Jockey]

I have used a number of methods to dry wood. I currently use an old Beko freezer,stored under cover outside. I have run power to it and installed 2 scones which take incandescent light bulbs(can still get on ebay). Drillied a 2" inch hole towards the bottom of the freezer to allow cool air to enter and a 2" hole at the top to allow the warm moisture air to escape. I generally use 2 60w bulbs and have installed a thermo cut out switch set to 49deg C.

 

[martin.pearson]

I haven't done it myself but do have this little book on the subject. It details what to do and how long the process takes, equipment, etc. When I lived on the west coast there was a wood supplier of local woods that had a commercially made one. He was able to dry a couple thousand board feet of wood from fresh cut to 8% moisture in about 2 weeks with no losses due to splitting etc. It had low temperature heating blankets between each layer of stickered wood. You'll likely end up somewhere between the two extremes. Only difficulty I see with a vacuum bag is circulating the air and having a low spot for the water to collect for draining. Since moving here where trees are not easy to get I have put it on the back burner.

Pete

Oh I think I saw that book some time ago but at the time it wasn't easy to get in the UK & there isn't a kindle version just the paperback lol yes the airflow is the only real problem I think, the water I have covered, I have a degassing chamber that I think I could use for the water collection, this was just a quick test as I already have everything I need to try this. It will be just one board to see how it goes & likely not that well without the airflow.
For the volume of wood that I would be looking to dry a commercial unit is a non starter but I am confident I could build something that would do the job at a sensible price lol

 

[martin.pearson]

I have used a number of methods to dry wood. I currently use an old Beko freezer,stored under cover outside. I have run power to it and installed 2 scones which take incandescent light bulbs(can still get on ebay). Drillied a 2" inch hole towards the bottom of the freezer to allow cool air to enter and a 2" hole at the top to allow the warm moisture air to escape. I generally use 2 60w bulbs and have installed a thermo cut out switch set to 49deg C.

how long does it take to dry from green & how low can you take the moisture content? You haven't mentioned fans so I take it air circulation is just natural. Should be fairly easy to get hold of an old upright freezer & figure out a way to stack boards in it.

 

[Inspector]

A number of screen/mesh layers on both sides might be enough for circulation if you open the bag to let moist air in and out daily or more as needed. A radiant heater (externally) would help warm the wood and speed up the process. It should work easily through a bag. The author of the book used the big PVC pipes, 2'diameter range) to make chambers for drying turning blanks and had internal heat as the PCV insulates to some extent so external heat didn't work in them. If you can get to and maintain a near vacuum the water will be close to boiling at room temperature so will dry much faster than any other method. Should you make an attempt I'll be looking forward to hearing how it went.

Pete

Forgot to add this chart. Water Boiling Temperature vs Pressure in Vacuum Table Chart

 

[martin.pearson]

A number of screen/mesh layers on both sides might be enough for circulation if you open the bag to let moist air in and out daily or more as needed. A radiant heater (externally) would help warm the wood and speed up the process. It should work easily through a bag. The author of the book used the big PVC pipes, 2'diameter range) to make chambers for drying turning blanks and had internal heat as the PCV insulates to some extent so external heat didn't work in them. If you can get to and maintain a near vacuum the water will be close to boiling at room temperature so will dry much faster than any other method. Should you make an attempt I'll be looking forward to hearing how it went.

Pete

Forgot to add this chart. Water Boiling Temperature vs Pressure in Vacuum Table Chart

Yes I am well aware of the relationship between vacuum & boiling point of water thanks, 20 years in the Royal Navy as an engineer working with all sorts of vacuum systems lol
Heat yes for this small project I have a heating pad, the pad was supposed to fit inside the vac bag but it's just a little bit to wide so will sit under the bag, in some ways a plus because it's one less thing to try & seal lol. Hadn't thought about layers but I have bleeder/breather film that might work.
This is really just a quick test to see how things go. it wouldn't be economical to use this as a normal method, building a proper system would be the long term goal but obviously involves spending money & also takes up space lol

 

[Owd Jockey]

how long does it take to dry from green & how low can you take the moisture content? You haven't mentioned fans so I take it air circulation is just natural. Should be fairly easy to get hold of an old upright freezer & figure out a way to stack boards in it.

Most of my green turned pieces start out at circa 32%, and i generally bring them down to about 10%. However, my moisture meter does not reveal the true value on thicker pieces, so i also record the weight of the piece. Generaly after 4 to 6 days you get a feel for how dry the wood is, how much warping etc, before i do the final turn. If you were doing this on a commercial basis then yes fans would be a necessity to get even flow and drying. For my set up ,simple physics does the job well. It seems (from other youtube posters) that the key temperature for drying wood is 49 deg C. I can achieve this temp quite easily in the summer on 2 x 60w bulbs, but struggle in the Winter with the colder air feed.I also use my wood kiln to dry wood for my wood burner.

 

[spanner48]

". . starting to board . . Laburnum logs"??

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