Letting freshly bought timber adjust, general rules?

[Tetsuaiga]

I remember reading in the past how it can be important to let timber you've just bought acclimatize to the new environment its been brought into and allow it to stabilize.

Can anyone tell me what you do with your own timber, say if you were making furniture? How long should you leave it before working? How important is it to actually wait?

Thanks

 

[JustBen]

Hope you don't mind me adding a question to your list.

How do you compensate for timber that will end up in a warm home that is stored in a workshop/garage that is usually cooler?

 

[Cheshirechappie]

The answer is a very firm and definite 'it depends'. It depends on the moisture content of the purchased timber relative to it's final home, it depends on the species of timber - the harder ones usually take longer to stabilise, it depends on how long the timber has been seasoning and thus how mellow it has become, it depends on the exact grain structure of individual boards (wild grain is often less stable).

In general, the longer timber can be left to stabilise in the conditions in which it will see service, the fewer the eventual problems. If you can rough components out full on width and thickness, then put them in stick in the warm room for a few weeks, you should be OK most of the time. That isn't always possible; in which case, try to take account of likely movements in the method of construction used - buttons for tabletops, allowance for panel shrinkage in frame-and-panel work, that sort of thing.

 

[Tony Spear]

the harder ones usually take longer to stabilise,

but the softer ones tend to move much more than hardwoods..........

A couple of years ago, I was in a branch of Wickes whilst they were replenishing their shelf stock of "pine" from a great load of stuff from their yard outside, and I'll swear to it that you could see it moving as they put it on their racks! :shock:

So, as an experiment, I brought home the "best" 8ft. length of 2" x 4" they had and just stuck it behind the sofa for a couple of weeks. Having forgotten about it for a while, I dug it out and it had bowed over the lenght by about 6", difficult to accurately measure the other changes, but I guessed at about 1/4" cupping and about a 30 deg. twist over the full length!

 

[Andy RV]

I think you need to start with this before you even get the wood home, and buy that I mean don't buy from the DIY sheds! Buy from a merchant who actually knows how to deal with timber and store it correctly, the quality of the material will be better, it will be dry, it will be stored undercover on flat racking rather then on end.

 

[mac1012]

I have a similar problem with the pine I got from my timber merchants they store it flat under cover , one batch I had was fine , but the second length I got a while after displayed some cupping after a couple of weeks

I think I maybe that the two different lengths had different moisture content and reacted differently to the home environment , I was thinking of getting a moisture content meter but I don't think they would take kindly to me sticking pins into their stock :shock:

next time I going to try storing it under the bed flat see that makes any difference.

 

[Sgian Dubh]

the harder ones usually take longer to stabilise,

but the softer ones tend to move much more than hardwoods..........

One thing most people don't realise, or perhaps forget, is that the softwoods purchased from builder's merchants, DIY places, and the like are dried to a different target moisture content than hardwoods that are kiln dried for furniture type constructions: air dried hardwoods are a different story because wood air dried in the UK will seldom come down below about 18- 20% MC . Softwoods sold at these outlets are dried for the construction industry with a target MC of 20% ±2%. There are several reasons for this:
*Critically, 20% MC is the dry rot safe limit.
*If the wood is used in a residential building it will continue to dry out in situ, e.g., in the walls, studwork, and so on.
*And if it's used in uninsulated or poorly insulated commercial buildings its moisture content won't change too much from the 20%.
*There are more, but that will do to start with.

There are softwoods dried to a lower target MC suitable for furniture making, i.e., about 11- 12% MC in Europe (and about 7% ±2%MC in North America), but it's not available from the DIY and builder's merchant type outlets-- you need to go to a merchant that supplies this grade of wood.

As to tetsuiga's original question on whether or not you acclimatise your wood, it depends on its current MC, and its intended end use. If it's quite or very wet then acclimatising it is necessary for indoor furniture, but not necessary for outdoor artefacts. Very wet for internal furniture is something 14- 15% MC or greater. But if it's below that you can go ahead and make your furniture, but you'll need to make allowances for shrinkage in service, e.g., as cheshirechappie mentioned, such strategies as using buttons or expansion plates for table tops, allowing for panels to shrink within their framework, etc.

There's a lot more to know about allowing for wood movement in a wide range of end use situations, and even during construction than you can learn in a few quickly dashed off posts in a forum, particularly as the majority of respondents have very little understanding of the subject you asked about in particular, and timber technology in general. You can get an awful lot of bum steers if you're not careful, but that isn't the case in the already posted responses here. Probably your best bet if you really want to get to grips with the subject is to read a book on it. A good one is Understanding Wood by R Bruce Hoadley. Slainte.

 

[blackrodd]

20%moisture is about what you will find with outside stored softwood these days in the winter.
Merchants, leaving timber to get wet outside, doesn't help.
This timber is "5ths" grade, used for most of the building industry
This starts off as 6"x3" 0r 7"x3"and "deepcut on the re-saw to make 6" or 7"x1 and then into the 6 cutter moulding machine for square edge, skirting, set up with splitting saws for 3" and 2" mouldings etc.
Most joiners and furniture makers buy a far better grade, its more stable but very expensive. It is bought in and stored for use, and the workshop is kept at a steady temperature
The best grade, sometimes refered to as "sideboards" is the best, it has a crown stamped on the end. It is kiln dried, will have "live", if any knots and can be cut with very little movement. It is stored dry and kept dry.
Timber, taken from outside, at 20+% will more than likely "move" quite a bit after being taken indoors at 8%-10%or even 12%, depending on your're central heating settings.
Ideally yer timber should come in a garage type area but well ventilated for a couple of weeks then rough cut the required sizes. acclimatise under the bed or similar, preferably whilst the wife is out. about 3-4 weeks. Any planing needs to be as equal as possible from opposed sides as this can cause major problems.
Air dried timber is more difficult to use as any propeller maker will tell you.
Hardwoods, Always try and pick the timber yourself. go for the mellower if possible, lift one end and give it a "whip" if it bounces its mellow and pretty stable, the whole tree can mellow, and tends to have good medullary rays in the figuire. Excellent for table tops/ wider boards. If the board is rigid and not "whippy" it is best for the bigger, thicker components as the smaller you make it the more problems can be expected.
I went to night school and college and read lots of books. I make country furniture in elm, oak and ash etc, and the above works for me. as my mentor said to me, in theory if you put you're feet in the cooker and you're head in the fridge every thing will be equal! Rodders

 

[RogerP]

............acclimatise under the bed or similar, preferably whilst the wife is out. about 3-4 weeks. ...........Rodders

I've gotta get the wife out the house for 3/4 weeks? :shock:

 

[Mr T]

Hi

As usual Richard seems to have covered all the bases.

When I used to teach evening classes in schools movement was a constant problem when students worked in redwood. They would flatten the board one week and it would be cupped the following week. This was not such a problem with hardwood, which is why I would recommend working in hardwood over softwood.

I think most people worry about timber being too moist, however I have found that one wood local supplier, who keeps it in a heated warehouse, is measuring 5% MC. So the wood moves because it is absorbing moisture, the same problem but for different reasons.

Moisture meters aren't so expensive nowadays!

Chris