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Moisture content of wood query

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OldWood

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I collected today two lumps of holly which came from a dead straight 10ft by 7 to 8 inch diameter section lying on the ground since it was felled we don't know when. The sections I have are 3ft long and weigh 60 lbs +. For all intents and purposes the volume is 1 ft ^3 (OK it's 0.92, but who's arguing?) and I see from a googled table that the density is 47 lbs per ft^3, so something like 15 lbs of the weight is water.

Am I right in assuming that the dry weight the tables will be quoting for all the woods in it will be in the order of 10%, so that In this case around 5lbs of water will remain when the wood is 'dry' ? The humidity meter (OK it's a cheapy off Ebay so won't be that accurate) says 30%. Am I then being a bit naive in saying that if 10% equals 5lbs, then the 30% = the 15lbs I'm getting from the weighing machine ?

The second question is what would have been the moisture content at felling ?

And the third question, what would the panel's recommendations be on drying the wood, having heard that holly is an unfriendly wood for that.

Rob
 

CYNNYC

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Hello R,
No mate you didnt leave your boots lol. I.
Hope the gents are able to advise us as wouldnt want to lose this wood.
 

chipmunk

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Hi Rob,
I've been struggling to dry quite a bit of holly recently of similar sizes and it's not easy to stop it checking and the oxidation/going grey.

My current best advice would be to band or chain saw it lengthways down the pith unless you want to turn it green.
Then cut back the ends to remove any end checks and seal the ends with PVA/wax etc as normal. This should help you to dry it without checking but the greying/oxidizing seems more difficult to prevent.

As an experiment for my most recent batch I have tried treating the cut faces with lemon juice (jif in a bottle) to see if that stops the greying but it's too early yet to say whether that'll work or not.

Your estimates of the water content seems about right but wood's very variable and so it will almost certainly be a few pounds either way of the theoretical figures for both water and wood. My attitude would be don't worry about the numbers. If you weigh it regularly when it reaches EMC it'll stop getting lighter ;-)

HTH
Jon
 

OldWood

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chipmunk":8hh01i2o said:
Hi Rob,
I've been struggling to dry quite a bit of holly recently of similar sizes and it's not easy to stop it checking and the oxidation/going grey.

My current best advice would be to band or chain saw it lengthways down the pith unless you want to turn it green.
Then cut back the ends to remove any end checks and seal the ends with PVA/wax etc as normal. This should help you to dry it without checking but the greying/oxidizing seems more difficult to prevent.

As an experiment for my most recent batch I have tried treating the cut faces with lemon juice (jif in a bottle) to see if that stops the greying but it's too early yet to say whether that'll work or not.

Your estimates of the water content seems about right but wood's very variable and so it will almost certainly be a few pounds either way of the theoretical figures for both water and wood. My attitude would be don't worry about the numbers. If you weigh it regularly when it reaches EMC it'll stop getting lighter ;-)

HTH
Jon
Hi Jon and thanks.

But I will have to start by asking what your 'EMC' is - from the my working days it is 'Electro Magnetic Compatability' (possibly more easily understood as Radio Frequency Interference), neither of which have much dealings with wood and it's moisture content. I don't want to specifically rattle cages about the use of TLA's (three letter acronym), but it's not that I've forgotten what your EMC means, I've just never met it before and I've never seen it mentioned on these pages.

Knowing what it means is relevent I think as I'm going to get a gash sycamore log from an outside pile, and see if drying it out with the microwave method proves my arithmetic, but I need to know when to stop drying. The relevence of the airthmetic is to possibly get a handle on where this wood is in it's drying out - that is just how wet (how much water did it contain) when it was when it was felled.

Re. oxidation, I follow your logic on the use of lime juice, and this helps to understand your thinking

http://www.hometrainingtools.com/acid-k ... sh/a/1461/

I've used vitamin C, (as asorbic acid) which the body uses as an anti-oxidant, when extracting apple juice to prevent browning with success, though a change in procedure produced a cap of froth over the juice which stopped the air getting to it. It's a question then if the chemical would be more effective than the fruit juice, and possibly how to apply it!

What I have heard , and don't know if it is urban myth, is that in the old days they would soak holly in a river for a year to presumably remove the sugars from the wood (saccharides?). I'm wondering if this wood I have has lain long enough in damp grass to go the same way, but have no way of proving that. There's no checking at the ends yet.

Rob
 

chipmunk

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Hi Rob,
EMC = Equilibrium Moisture Content.

Sorry, shouldn't have used that TLA (three letter acronym ;-)
Jon
 

OldWood

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Ian
Thanks - that certainly confirms that a) it is difficult to dry and b) it is prone to staining - the latter I didn't know.

It would appear that the staining is fungal rather than chemical as Jon was attempting to address with lime juice (vitamim C), though the high acid level might be effective against the fungus.

The path I'm pursuing is how much the wood has seasoned naturally since it was felled with the current moisture reading being 30%. My reading on the internet would indicate that this EMC figure (Equilibrium Moisture Content) which is the moisture content of any hydroscopic material within the environment that it is in, so if the temperature is high and the RH% is high then the EMC is high, and the converse for low temperature, etc. Typically at 60F temperature and 50% RH the EMC is around 10%, which is what we would like to work it at.

I'm assuming that the humidity meter I have is giving me the EMC reading. I do have to accept that it was a Chinese cheapy, and will correspondingly give me an indication rather than an accurate measure.

I've now read a small part of the Wikipedia article on Wood Drying http://en.wikipedia.org/wiki/Wood_drying which is long, comprehensive, and technical but in a quick scan through doesn't help us that much.

What it did tell me though was that at 30% EMC, the free water in the cell tubes (lumens) is likely to have gone (50% EMC at felling typically) and the water now present is that tied in chemically in the cell walls, which is the difficult water to get rid of as that in the middle has to move through the whole radius to escape, so the split down the middle suggestion is very valid.

Found my boots, outside and full of rain !

Rob
 

chipmunk

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Hi Rob,
The splitting/cutting of the logs down the middle isn't so much to improve the drying, although it does and this may in fact be a disadvantage, but rather it's done to prevent the wood from splitting as it dries.

As timber dries it shrinks more in circumference than in radius. This sets up stresses in the logs which if left are eventually relieved by end checking from the pith to the outside and "sods law" states that these checks will certainly be at different points of the circumference at each end of the log which wastes timber.

If the logs are halved then the drying stresses are much reduced and when dry there will be a noticable bump at the pith and rather than being semi-circular in cross-section it'll look more like a pie-slice of around 170 degrees.

It always amazes me when you put the two dry halves together because at this point you can see how big the check/split would have been and it's usually pretty big ;-)

Hope this helps
Jon
 

chipmunk

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Hi Rob,
The greying in my holly is almost certainly oxidation of the sugars in the wood rather than fungal (spalting), which is why I'm trying the lemon juice idea.

I have another couple of holly trees to fell and am waiting to do it later this winter when the saps well down, to see if that helps the oxidation issue.

Jon
 

jpt

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I have dried quite a bit of holly over the years and apart from splitting the logs to get rid of the pith the important things are that it is stored standing up and away from other wood. This is the only way I have found to stop it changing colour.

john
 

OldWood

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I think the path I will take from all the advise that is around is to cut the timber into bowl appropriate lengths (it is ~180mm in diameter), take the bark off on the lathe and then split it lengthwise.

Does zapping wood in the microwave kill organisms down to spore level even if the burst of energy is short so that it doesn't damage the wood at all ?

The EMC does have to be reduced to <18% to stop the fungus, so quite a lot of water does have to be got out to get it down to that level - a 900mm length of 180mm dia. is going to yield 8 bowl blanks so the best part of a 500 gms of water has to be got out of each one for 10% EMC, and a bit over a half that get it to the level where the fungus will be stopped.

I've just been watching Nick Arnull's excellent DVD Ying (the 2nd one of the set 'Yang' hasn't been tackled yet). He makes a pierced piece out of wet sycamore - interesting to know whether holly would work for this too - 2mm wall thickness.

Rob
 

Roger C

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:D Hi Guys the discolouration you get in holly and other woods is sap stain. There is a liquid that is used by sawmills planking logs to prevent sapstain. It can also be used on logs and split logs. In South Africa we use a lot of pine and the mills use this {antiblue } name used in the trade.After applying anti blue, seal with a water soluble wax sealer. In USA anchor seal. In RSA Hydro wax. To remove stains in wood use oxcalic acid, can be purchase at your local pharmacy. Mix a paste using water and apply to the stained area and leave for a few minutes and then wash off with water. The stain will be removed, only a few millimeters deep about 2-3.Trial and error. Best do it before final sand and before applying finih. This hydro wax can also be used to seal part turned projects. Regards Roger C in RSA. :D :D
 

OldWood

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Roger C":pgp2yrhb said:
:D Hi Guys the discolouration you get in holly and other woods is sap stain. There is a liquid that is used by sawmills planking logs to prevent sapstain. It can also be used on logs and split logs. In South Africa we use a lot of pine and the mills use this {antiblue } name used in the trade.After applying anti blue, seal with a water soluble wax sealer. In USA anchor seal. In RSA Hydro wax. To remove stains in wood use oxcalic acid, can be purchase at your local pharmacy. Mix a paste using water and apply to the stained area and leave for a few minutes and then wash off with water. The stain will be removed, only a few millimeters deep about 2-3.Trial and error. Best do it before final sand and before applying finih. This hydro wax can also be used to seal part turned projects. Regards Roger C in RSA. :D :D
Many thanks Roger - it'll be interesting to find if this is a problem in the UK that the timber millers face; wetter here but not so warm.

I found a website for the stuff you mention

http://www.archchemicals.com/Fed/WOLW/P ... efault.htm

The oxalic acid use is useful as well - thanks

Rob
 
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