Thread: Jarrah - properties of a fresh cut large slab

Originally Posted by michhes

Hi all,
Am curious to hear your thoughts and experiences working with very thick jarrah slabs--4-5 inches thick and 2-3 feet wide.
This may be a silly question but does jarrah need to dry as much as other words before milling?

I mill all my logs as green as I can get them EXCEPT
- Big spotted gums: I like to wait for the bark to start to fall off
- Pine: where I also wait for a few months in the vain hope that I won't get as much resin spreading from anus to breakfast.

Is a slab this thick likely to move and check very much over time as it dries naturally?

Provided Jarrah is well stickered and stacked, the thicker the slab the less it will move.

Finally, are there typically any concerns with jarrah sapwood versus the rest of the tree?

Only that it is a bit more susceptible to borer and other bug attack. Wood working wise it should be OK. We have jarrah floor boards with sapwood in our 95 year old house that are still perfect.

I'll reveal my reasons for asking and the detail the application but first I'd like to hear your unbiased stories as the application may be unexpected!

Biassed responses are free, but no different to my unbiassed ones.

Thanks for your thoughts BobL. From some of your other photo posts it looks you get a great deal of joy out of the milling process! Would love to join you one day--am 'retiring' to be a stay at home dad in July.

Sorry, I should have been clearer when I used the term 'milling'--I was referring to flattening the slab/etc (jointer/planer) once cut from the log. In specific reference to jarrah, should I allow a freshly cut, 4-5" thick slab significant time to dry (air dry) before flattening)? Is jarrah as likely to move as any other wood as the moisture content changes following the initial cut? I could store the slab reasonably flat in the garage but wouldn't have the weight of the stickered pile keeping it from dancing around.

Btw, my 'exotic' application is a workbench (but for use--not display/collection): Carpenter's Work Bench ref. 12021 | French antiques | Négrel Antiques

Originally Posted by michhes

to jarrah, should I allow a freshly cut, 4-5" thick slab significant time to dry (air dry) before flattening)?

Unless it is kiln dried the the old rule of thumb of 1" per year is a safe one to stick to although I think the difference between summers and winters here is so high that a better rule might be one summer per inch. Hence a 3" slab could take as little as 2.5 years to air dry

Is jarrah as likely to move as any other wood as the moisture content changes following the initial cut? I could store the slab reasonably flat in the garage but wouldn't have the weight of the stickered pile keeping it from dancing around.

I don't think it moves any more and maybe slightly less than other timbers, especially if it is clear grained and stored flat. Where it comes from on the log is pretty important for most timbers. One thing I would suggest is not to leave it in a totally closed garage. Some ventilation is required or it could go mouldy and take longer to dry.

my 'exotic' application is a workbench (but for use--not display/collection): Carpenter's Work Bench ref. 12021 | French antiques | Négrel Antiques

That is indeed a very nice bench. I have thought of using a single slab for a workbench top but the since the chance of a whole slab moving is greater than one made up of multiple pieces I'm not sure I would risk it. For dining tables and such applications if the top moves a mm or two across the width then it will not be as detrimental to the operation of the table as it would be for a work bench . I guess that is the risk you will have to take.

To reduce your risk you could put the slab in the location where you wish to use it and monitor it's movement over one year and see what it does. If it does not move much in its raw state then the chance of it moving in a finished state will be even less.

I'm not sure if I would call that design exotic, especially since there would have been hundreds or may thousands of those made over the centuries. I've seen half a dozen old ww bench tops made out of single slabs in the Italian alps, some of the slabs must be around 8" thick. Maybe "traditional" is a better word.

I have just picked up 7m of 200 x 50 Jarrah from a recycling place. i was hoping that their wood was under cover but unfortunately it is stored out in the open.

How long should I let the plank sit in the shed prior to dressing down? I stuck it with a moisture reader in the end grain and got 6%.

I ask because we have had a real wet few months here but 6% seems pretty good, any suggestions?

6% is considered immediately "dry and workable". In fact inside a house will be warmer and thus more humid so if you bring it indoors you may find it's MC goes up!

Originally Posted by RicB

I have just picked up 7m of 200 x 50 Jarrah from a recycling place. i was hoping that their wood was under cover but unfortunately it is stored out in the open.

How long should I let the plank sit in the shed prior to dressing down? I stuck it with a moisture reader in the end grain and got 6%.

I ask because we have had a real wet few months here but 6% seems pretty good, any suggestions?

Good Morning Ric

Many years ago I worked in the timber industry and the industry norm was to dry over 90% of timber to 12% moisture, a small percentage destined for furniture for air conditioned offices was dried to 8%.

Your reading of 6% is abnormally low - are you sure it's accurate?



FairWinds

Graeme

Originally Posted by GraemeCook

Your reading of 6% is abnormally low - are you sure it's accurate?

not anymore

I have a cheap moisture meter, a German made jobbie but still a cheapie, two prongs that I stuck in the freshly cut end grain - 6%, repeated a couple of times - 6%.

I haven't tested my moisture meter in the end grain to see what readings I might get, but the normal method is to insert into the long grain.

Originally Posted by KevM

I haven't tested my moisture meter in the end grain to see what readings I might get, but the normal method is to insert into the long grain.

Yeah, that was the first place I tried but I got "zilch", and I figured that can't be right..

Originally Posted by RicB

Yeah, that was the first place I tried but I got "zilch", and I figured that can't be right..

How deep did you insert the pins?

The accuracy of the cheaper pin type MC meters at the low end of MC is typically +/- 2% MC so 6% could be 8% MC.

Originally Posted by KevM

How deep did you insert the pins?

I tried to stick them in quite hard but bearing in mind this is recycled Jarrah and the meter is quite small with a palstic body, you can only push so hard before having to order a new meter. Needless to say, I didn't just "lay" the prongs on the wood.

Originally Posted by RicB

I tried to stick them in quite hard but bearing in mind this is recycled Jarrah and the meter is quite small with a palstic body, you can only push so hard before having to order a new meter. Needless to say, I didn't just "lay" the prongs on the wood.

Cut a piece off, halve it and then plunge your prongs into the fresh long grain edge to get a reading. Although this will only give you a reading for the end of the board and not the centre.