English Oak - high moisture content - advice please!

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RogerM

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About a year ago I bought some wany edge English Oak boards, about 1" to 1.25" thick, by an average of 22" wide, from a land owner who told me that they had been air-dried for the previous 2 years under cover in an open ended barn, which is where I viewed them, and they had clearly been there some time. For the last year they have been stacked in the garage separated with 1" sticks (offcuts from the same boards).

Today I started to prepare a cutting list for a tall bookcase with a 2 drawer base unit, and the finished timber will finish up 3/4" thick - the intention being to stack the roughly thicknessed timber (thicknessed to 7/8ths) indoors for a few weeks before starting work. I even got the camera out to start a WIP thread with loads of piccies. However my newly acquired Wagner moisture meter gives a moisture content (after applying the species adjustment factor) of 23%. This is disappointingly high and clearly not ready for furniture making. So what do I do?

1. Continue to stack the cut list in the garage as sawn boards.

2. thickness it sufficiently to get it to an even thickness (say 7/8") and leave it in the garage.

3. thickness it to 7/8" and store it indoors.

I guess that the cold wet summer has done me no favours. If I store it indoors, how long would 7/8" take to dry from 23% down to a usable level of (say) 15%. Our existing oak furniture gives an adjusted MC of 13.5%. I have 25 cu ft of this stuff (MC aside, it's absolutely gorgeous wood) but the frustration in not being able to start using it now is huge!

All constructive advice gratefully received.
 

Ironballs

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I'd say number 2 is probably your best bet, most days the humidity has been incredibly high this summer, even when warm and it's not likely to get any better.

There are other things you can try with enclosed spaces and heaters or dehumidifiers, but bringing indoors is probably easiest - if you have the space of course
 

MikeG.

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Given the notorious unreliablitity of moisture meters, might it be worth trying for a second opinion? Maybe take a sample to your local timber yard and see what they reckon.......
 

les chicken

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Roger

I would say that the problem you have is that the wood has aclimatised itself to your garage. When wood is air dried as in an open ended barn, it is the air flow across the wood that dries it out. In the garage there is no air flow so the wood will absorb moisture but not so easily give it up.

I have noticed this before when I put wood in the garage to dry out I found that the wood left outside sticked under cover with plenty of air flow was drier than the wood in the garage.

As the weather is supposed to be improving over the next week, try sticking it outside and under cover for a week or so and then try the moisture meter on it.

I could be totaly wrong but in the experience I have had it could well be worth trying. You could then rough it to size and store it in doors for a while. If you rough it to size with that moisture content you might end with with wooden fish hooks, (totally warped wood due to stress relief)

Les
 

bjm

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Roger

Air dried timber will usually reach an equilibrium between 16-20% mc if kept covered from the rain. Given the length of time and the thickness it should be around that figure regardless of recent conditions. Although it may have been in an open-ended barn there may not have been sufficient air movement to dry it at a suitable rate. If so, then it would have been wetter than you suspected and has only been drying since you bought it if it's still at 23%.

If the reading is correct then I'd rough cut it thicker than you suggest (bearing in mind it will shrink) and bring it indoors to acclimatise - hopefully you haven't got the heating on yet so it shouldn't be too much of a shock!

Brian
 

woodbloke

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Roger - frustrating to say the least :x I think I'd leave it a bit longer under cover with a decent air circulation. Under the best conditions in this country, air dried timber will only come down to about 20% MC and will require a further period of secondary conditioning in a moderately warm room to bring it down to about 15% or so. It might be worthwhile to take an off-cut of the timber, test it with the meter and then bring indoors for say, a month and test again...it ought to have dropped a bit.
A cool bedroom is ideal for this sort of thing...25cu' of oak in your master suite should please SWIMBO :lol: 8-[ - Rob
 

OPJ

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I agree with Rob's advice.

I can't understand why people advise thicknessing the stock first before stacking it indoors? Skimming 1mm off each face to get a clearer picture of the grain patterns, fair enough. But why take it down to a set size when, if it moves badly after further drying indoors, you'll only have to remove more timber to get it flat and true later.

If you can thickness 22" wide boards though, Roger, then I'd love to see a photo of your thicknesser!! :twisted: :wink:
 

mpooley

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Are moisture meters unreliable?

can anyone recomend one which wont break my budget of not a lot!

and is it worth getting one at all or should i just trust my supplier lol


Mike
 

RogerM

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John McM":ifrtnan5 said:
http://www.getwoodworking.com/news/article/mps/uan/43

http://www.getwoodworking.com/news/article/mps/uan/44

John - thanks for those links - very useful. and thanks to all you guys for all your suggestions.

This morning I did a did a MC check by putting a block of the oak in question in the microwave for 5 mins at a time, and took it out at the end of each period to weigh it and to do a moisture check. To avoid the the fire hazard I kept the setting down to "warm" which is the one below "simmer", and the lowest our microwave will go. This appeared to be quite effective as I had the MC down to 8% by the time it caught fire! SWMBO is out for the day (do you think I would have been allowed to use the microwave otherwise?) and having kept all doors and windows open, and wiped down every surface, the smell may be almost bearable by the time she gets home! :(

As for the timber, I have decided to cut it roughly to size for my bookcase project, and leave it sticked in the garage with both front and rear doors open to allow a draft through whilst the reasonable weather lasts, but to stack it in our back bedroom come autumn. I'll monitor the MC weekly and hopefully by Spring I'll have some usable timber.

In the meantime I need to decide on whether to buy some kiln dried timber for an immediate smaller project, and what else can be done to get rid of the smell in the kitchen. I'm off now to don my kevlar jock-strap before SWMBO gets home.
 

MikeG.

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I like this approach Roger!!! I like it a lot! That has brought a smile to my lunch-break!

It made me think......

........if you happened to have wooden platters, and you "inadvertantly" allowed your meal to go cold, you could "accidentally" cause some pyrotechnics simply by re-heating in the micro-wave.

That could liven up a dull evening!!!

Mike
 

Sgian Dubh

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RogerM":p0jl71ov said:
I did a did a MC check by putting a block of the oak in question in the microwave for 5 mins at a time, and took it out at the end of each period to weigh it and to do a moisture check.

Here's a safe way to check the moisture content of wood in a microwave.

Edit. Since originally posting I went back to my original manuscript on the subject and did some editing to make it read better. Here's the new version. Slainte.

Microwave Oven Drying

Oven drying in a microwave oven takes between 20 and 45 minutes. 30 minutes is about average. It saves a great deal of time over drying wood in a regular oven. It does however require care and attention to details. Poor methodology and mistakes in the procedure usually lead to problems and failure.

You need to weigh the wood samples and electronic postal scales purchased at reasonable cost from an office supplier I find work well enough for my needs: if you require more accuracy then better, more expensive scales are required. My scales provide readings in 1 gramme divisions from zero up to a maximum of 2200 grammes, and I can select readings in either grammes or ounces.

To dry the wood I use a turntable type microwave oven that has several power settings. The only two settings I use are the very lowest setting and the next higher setting which is Defrost – your oven is likely to have a different configuration, but whatever marked settings are available restrict yourself to the lowest one or two power levels. As the wood is heated moisture evaporates from all exposed surfaces, including the bottom face resting on the turntable; three to five paper kitchen towels laid under the wood absorb and dissipate the condensed moisture drawn downwards from the wood. If you’re testing several samples make sure they don’t touch each other because this can concentrate the energy and can lead to smoking and possibly fire.

If the wood starts to smoke at any time during the drying procedure the sample is ruined and you need to start again with a new sample. Smoking during the cooking means you have burnt away some of the wood volume and weight measurements taken thereafter are inaccurate. This is why I mostly restrict myself to the lowest power setting and short bursts of heat. The second lowest power setting, Defrost on my microwave oven, is seldom used, but I do sometimes use it for the initial drying cycle of very wet wood.

The ideal wood sample is a full thickness and width piece taken at least 400 mm in from the end of your board that is 25- 32 mm (1” to 1-1/4”) long. Wood near the end of a plank or board is unrepresentative of the board as a whole—moisture exchange is more volatile at a board’s end than nearer the centre. Weigh your sample and make a note of this. If the sample is already partially dried, eg, about 25% MC to 15% MC, cook the wood at the lowest oven setting for between one and a half and two minutes in the first cycle.

If you know the wood is already below 10% MC I recommend you cook it at the lowest setting of the oven for no more than 45 or 60 seconds to start with.

Where wood is definitely at fibre saturation point (FSP, 30% MC) or above it’s my experience that the first cooking should last no more than between 1-1/2 and three minutes with the oven at the second lowest setting. Even in this circumstance I prefer to use the lowest oven setting: it takes a few minutes longer to dry the wood but I prefer that to starting again because I’ve burnt the sample.

After the first cycle weigh the sample or samples again to form an impression of how quickly the wood loses weight, ie loses water. Let the sample rest for a minute or so and re-cook it for between 45 and sixty seconds and re-weigh.

Continue with this routine until you can’t measure any weight change, i.e., less than 0.1 of a gramme variation if you are using highly accurate scales. My scales read only to the nearest gramme so I stop cooking when I get five or six low weight readings the same.

When this point is reached use the formula MC% = (WW–ODW/ODW) X 100, where WW is Wet Weight of the sample, and ODW represents the wood sample’s Oven Dry Weight.

The following cautions should observed.

Do not use high microwave oven power settings. The internal heat built up in the wood needs to dissipate and high settings cause rapid heat build up, smoke and even fire.

The more wood tested in one go, the more time is required to complete the job. This is useful because after the initial heating of a large batch you can rotate from one sample to the next in the oven with short bursts of cooking for each piece. This gives each sample a break between heating cycles thus reducing the chance of overheating any one piece.

It’s my experience that kiln dried wood samples react differently to cooking than green or air dried samples. It’s easier not to mix samples of very different moisture contents and different wood species during the test, but it's possible if you proceed with care.

Being sure that the wood sample or samples is, or are, truly oven dry requires patience and careful weighing using accurate scales. It’s better, and safer, to use several short cycles in the oven at low settings than it is to try and rush the job using a higher setting for extended times. The latter strategy usually results in burning the wood and failure.

The following final closing warnings probably seem obvious, but they’re worth repeating. Removing cooked wood from the oven requires care. It’s usually hot and can and does burn skin – you probably don’t need to ask how I know that! Use an oven glove or heavy leather work gloves. Also be aware that at the end of testing, and unknown to you, wood might have charred on the inside: it can smoulder and burn, and could set fire to rubbish in bins, etc. Careful disposal is essential. The safest thing is to put the cooked wood in water when you’ve finished to ensure it doesn’t burst into flames later—it can happen.
 

bugbear

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Sgian Dubh":tpo5pmsc said:
RogerM":tpo5pmsc said:
I did a did a MC check by putting a block of the oak in question in the microwave for 5 mins at a time, and took it out at the end of each period to weigh it and to do a moisture check.

Here's a safe way to check the moisture content of wood in a microwave. Slainte.

This only leaves the question of where you cut your to-be-ovened sampled from.

Presumably the most representative sample is right from the middle of your nice board, where you'd probably rather not cut.

But the ends (where you wouldn't mind cutting) aren't representative.

How does one proceeed?

BugBear
 

Sgian Dubh

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bugbear":er8r0c2r said:
This only leaves the question of where you cut your to-be-ovened sampled from.

Presumably the most representative sample is right from the middle of your nice board, where you'd probably rather not cut.

But the ends (where you wouldn't mind cutting) aren't representative.

How does one proceeed?

BugBear

All true BugBear. 300- 450 mm in from one end is a good place to cut out a sample. Where to select your sample is, as you say, a question of where you can afford to lose a bit of wood. Sometimes you're able to cut a bit out near a knot that you're going to discard. Sometimes you can see there's a cross section available where you're going to make a cross cut anyway. At other times, most frequently in my experience, there's no need to do the oven drying test. A pin or pinless meter is close enough, or you know the wood is dry because it's been kilned and stored somewhere dry.

The oven drying test is primarily a tool of the kiln operator or timber technologist, but it's sometimes useful for the woodworker. It's definitely useful for students of practical woodworking to help develop understanding of timber technology principles. Slainte.
 

RogerM

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Sgian Dubh":1m381jx2 said:
..............Do not use high microwave oven power settings. The internal heat built up in the wood needs to dissipate and high settings cause rapid heat build up, smoke and even fire.

....................... wood might have charred on the inside: it can smoulder and burn, and could set fire to rubbish in bins, etc. Careful disposal is essential. The safest thing is to put the cooked wood in water when you’ve finished to ensure it doesn’t burst into flames later—it can happen.

Yep - I can vouch for that. My sample started burning on the inside and was sending out a jet of smoke at high velocity through a crack in the wood - a bit like those SciFi films of jets of vapour coming from a comet on collision course with Earth. Here are the remains of my sample after I had knocked through to the burnt out core. When I threw it outside it carried on smoking vigorously for about 5 mins.

DSC01280.JPG
 

Sgian Dubh

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Tusses":288exv6m said:
no one has mentioned vacuum drying yet ???

Vacuum drying is not a common method. It works but as yet it is primarily experimental from a commercial point of view. Slainte.
 

Sgian Dubh

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RogerM":z3o42cd2 said:
... Here are the remains of my sample after I had knocked through to the burnt out core. When I threw it outside it carried on smoking vigorously for about 5 mins.

DSC01280.JPG

That's a perfect illustration of what can occur. Slainte.
 

Tusses

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Sgian Dubh":u60bx3ht said:
Tusses":u60bx3ht said:
no one has mentioned vacuum drying yet ???

Vacuum drying is not a common method. It works but as yet it is primarily experimental from a commercial point of view. Slainte.

so ... would it be worth experimenting with - if you had a vacuum pump for veneering for instance ?
 
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