How long would air dried oak take to dry to 11 per cent ?

[Charlie Woody]

I have been trying to source some kiln dried quarter sawn English oak without any luck. Just been offered some that has been air dried for about 10 years ..... not sure if it has been in an open sided shed or out in the open yet ..... so MC probably around 15 to 20 per cent.

Assuming the higher if I put this in my workshop where I run a dehumidifer 24/7 with a humidity range of 40 - 50 per cent, how long do you think it would take to get down to around 11 per cent?

 

[Chrispy]

In the olden days they used to recon on one year per inch thickness plus one year, so if your stuff is 1" thick then ten years is quite well done where ever its been.
What are you cutting from it? if your making chairs use it as is, if your making large wide table tops may be let it finnish off in your workshop for a few weeks/ months. I assume 1" thick. So what does it feel like when you cut a bit up? does it feel right?

 

[marcros]

if i were you, i would be tempted to buy a cheap moisture metre and monitor it on a weekly basis for a few weeks. It should only cost a few quid (£15? or so) but it is cheaper than having to buy new timber.

I have not used much air dried timber but it is said to be nicer to work than KD.

 

[Charlie Woody]

In the olden days they used to recon on one year per inch thickness plus one year, so if your stuff is 1" thick then ten years is quite well done where ever its been.
What are you cutting from it? if your making chairs use it as is, if your making large wide table tops may be let it finnish off in your workshop for a few weeks/ months. I assume 1" thick. So what does it feel like when you cut a bit up? does it feel right?

Its for a coffee table L 760mm W 380mm (made from 2@ 140mm & 2@ 50mm) T 38mm.

I have n't seen the timber yet but am told it's approx 50mm thick - sawn. I could get away with delaying it for a few weeks .... months would not be acceptable, unfortunately.

 

[Charlie Woody]

if i were you, i would be tempted to buy a cheap moisture metre and monitor it on a weekly basis for a few weeks. It should only cost a few quid (£15? or so) but it is cheaper than having to buy new timber.

I have not used much air dried timber but it is said to be nicer to work than KD.

I agreed with the sentiments Marcros, however, whilst searching the forum for answers to this dilemma, I came across some adverse comments on cheap moisture meters. I have n't used air dried English Oak before either, hence my concerns. Don't want to make a pigs ear of it

 

[marcros]

they should give a reasonable relative value. worst case, you drill a couple of test hole for the probes.

 

[Lord Kitchener]

Coffee table suggests that it is going to be used indoors. I don't think air dried timber is going to suit for that, especially as you don't know its history. A few weeks in a workshop isn't going to help much especially if it's 2" material.

 

[Charlie Woody]

Coffee table suggests that it is going to be used indoors. I don't think air dried timber is going to suit for that, especially as you don't know its history. A few weeks in a workshop isn't going to help much especially if it's 2" material.

I guess you have just confirmed what I suspected myself.

So the next question is where do I get 2" English Quarter Sawn Oak kiln dried in Devon?

 

[marcros]

I disagree that it is not suitable. The timber propbably needs to loose a bit more moisture to bring it down to about 7-10%. It is probably at about 15% now. Being quarter sawn helps with the stability.

http://www.robertthompsons.co.uk/FAQ.htm uses air dried stuff. true, they know more of the history but if the 10 year old stuff is stacked correctly, use some boards from the middle of the pile, dimension to just over the finishing size and sat in the workshop (or preferably house) for a few weeks and I think it will be fine. air dried has been used for centuries, and whilst they didnt have central heating, they would have had roaring fires in the winter which would probably give a greater temperature swing than we have now.

 

[Lord Kitchener]

air dried has been used for centuries, and whilst they didnt have central heating, they would have had roaring fires in the winter which would probably give a greater temperature swing than we have now.

It's not the temperature swing that is the problem, it's the humidity. A centrally heated house in the winter is a very dry place indeed.

In any case, it's not necessariily unsuitable, it's just a little bit risky, especially at that thickness. Does the OP feel lucky?

 

[custard]

It's not the temperature swing that is the problem, it's the humidity. A centrally heated house in the winter is a very dry place indeed.
quote]

For most Americans with their continental climate it's true that winter generally brings lower humidity, but in Britain's maritime climate we'll normally experience our lowest relative humidity in the summer. Here's a useful chart based on individual cities.

http://www.watkinshire.co.uk/assets/Fil ... e-data.pdf

You can then calculate the timber moisure content required to reach equilibrium at any particular relative humidity level by using a table such as this one,

http://www.csgnetwork.com/emctablecalc.html

 

[Lord Kitchener]

It's not the temperature swing that is the problem, it's the humidity. A centrally heated house in the winter is a very dry place indeed.
quote]

For most Americans with their continental climate it's true that winter generally brings lower humidity, but in Britain's maritime climate we'll normally experience our lowest relative humidity in the summer. Here's a useful chart based on individual cities.

http://www.watkinshire.co.uk/assets/Fil ... e-data.pdf

You can then calculate the timber moisure content required to reach equilibrium at any particular relative humidity level by using a table such as this one,

http://www.csgnetwork.com/emctablecalc.html

Well, if he is intending to have his coffee table out-of-doors then your links will prove very useful. Just in case he isn't planning an external coffee-drinking experience, do you have any links showing the relative humidity inside centrally heated houses?

 

[custard]

Well, if he is intending to have his coffee table out-of-doors then your links will prove very useful. Just in case he isn't planning an external coffee-drinking experience, do you have any links showing the relative humidity inside centrally heated houses?

Good point. I've had a humidity meter in a centrally heated workshop for many years. Same result in that winter is higher than summer, but the absolute variation is really pretty low, rarely straying out of the 45-55% range.

 

[Lord Kitchener]

Well, if he is intending to have his coffee table out-of-doors then your links will prove very useful. Just in case he isn't planning an external coffee-drinking experience, do you have any links showing the relative humidity inside centrally heated houses?

Good point. I've had a humidity meter in a centrally heated workshop for many years. Same result in that winter is higher than summer, but the absolute variation is really pretty low, rarely straying out of the 45-55% range.

Your findings are different to mine, then. Especially when the outside temperature drops to freezing or below.

 

[Sgian Dubh]

For most Americans with their continental climate it's true that winter generally brings lower humidity, but in Britain's maritime climate we'll normally experience our lowest relative humidity in the summer. Here's a useful chart based on individual cities.

custard, your link to the Watkins website provides figures for external temperatures and RH values in a number of UK cities. They are about what I'd expect. Temperature and RH values don't follow the same pattern inside British houses that have decent insulation, double or triple glazed doors and windows, and climate control systems: the reverse is the case where, specifically, RH values are lower in the winter than they are in the summer.

I've attached a JPEG of a graph showing readings I took twice daily inside our house over one year back in 2006-07. Notice there's a bit of blip in June to August figures which is a consequence of the very wet period that occurred in the summer of 2007, but didn't occur in 2006. If I'd taken the readings for several years and averaged them, the graph would be smoother. The purpose of the graph is to illustrate a timber technology manuscript and I wanted some first hand research for the text to back up secondary sources similar to the ones from the Watkins website. Slainte.

 

[Phil Pascoe]

In my dry weatherproof workshop the humidity varies from 55%-60% in the winter to 75%-85% in summer - just shows how different parts of the country vary. I stayed with my sister in Auckland a few years ago, and commented one day that the humidity was 85% - she said I should visit in the summer when it got damp - she had seen 99%!!

 

[Phil Pascoe]

I read some while ago a very detailed article on organ building in the USA, apparently their organs are built very differently to european ones, because the seasonal humidity changes are so great that european ones end up falling to bits.(I always remember that the guy who machined the holes in the smallest pipes was the company's dentist!)

 

[custard]

For most Americans with their continental climate it's true that winter generally brings lower humidity, but in Britain's maritime climate we'll normally experience our lowest relative humidity in the summer. Here's a useful chart based on individual cities.

custard, your link to the Watkins website provides figures for external temperatures and RH values in a number of UK cities. They are about what I'd expect. Temperature and RH values don't follow the same pattern inside British houses that have decent insulation, double or triple glazed doors and windows, and climate control systems: the reverse is the case where, specifically, RH values are lower in the winter than they are in the summer.

I've attached a JPEG of a graph showing readings I took twice daily inside our house over one year back in 2006-07. Notice there's a bit of blip in June to August figures which is a consequence of the very wet period that occurred in the summer of 2007, but didn't occur in 2006. If I'd taken the readings for several years and averaged them, the graph would be smoother. The purpose of the graph is to illustrate a timber technology manuscript and I wanted some first hand research for the text to back up secondary sources similar to the ones from the Watkins website. Slainte.

Data trumps opinion every time...so I stand corrected! Although I am surprised at the variation in your chart, however you hint that it's a bit skewed by untypical weather. In my workshop I'll see humidity spikes, a thunderstorm always sees the meter spike way up, but it's a temporary effect so it's actually pretty rare that I'll see any sustained departure from the 45-55% range.

One point though that might be worth noting, my experience is in a London workshop. In January I'll be moving to Lymington, with a workshop less than a quarter mile from the coast, and substituting a wood burner for central heating, so it'll be interesting to see what humidity variations I record there.

 

[custard]

I read some while ago a very detailed article on organ building in the USA, apparently their organs are built very differently to european ones, because the seasonal humidity changes are so great that european ones end up falling to bits.(I always remember that the guy who machined the holes in the smallest pipes was the company's dentist!)

:shock: :shock: :shock:

I had to read that twice!

 

[speeder1987]

Humidity is just the amount of water vapour held in air. As the temperature increases, the dew point increases, and the air can hold more water vapour. Therefore in winter the humidity will be lower.

Even if we are talking about inside, the air will be circulating from outside where the humidity will be lower ....... inside temperature won't make much difference unless you have a lot of standing water, a warm house and very poor ventilation

John

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