Specific Gravity - list of Aussie species?

[FenceFurniture]

Does anyone know of a list of Specific Gravity for Aussie timbers? Preferably one that is able to be copied and pasted into Excel?

This is for use with a moisture meter, and being a USA made product, they aren't aware that we have more than 2-3 species here (let alone about 700 Eucalyptus spp....). Also interesting to note that it can't be used with timbers >1.0 SG, which cuts out a lot of Aussies.

[BobL]

. . . . they aren't aware that we have more than 2-3 species here (let alone about 700 Eucalyptus spp....).

There are apparently 700 Euc species just in WA, and 200 in the rest of Australia. OK most of them are no more than stunted shrubs.

The densities of eucalyptus can be highly variable (the first one I looked at my CSIRO Forest Trees of Australian book on forest products says 755 - 1043 and another one says 740 - 1005 kg/m^3) and then even on the same tree the density can vary significantly. The only way around this is to measure the density yourself otherwise if you want a reliable comparative MC measurement.

[FenceFurniture]

The densities of eucalyptus can be highly variable (the first one I looked at my CSIRO Forest Trees of Australian book on forest products says 755 - 1043 and another one says 740 - 1005 kg/m^3) and then even on the same tree the density can vary significantly. The only way around this is to measure the density yourself otherwise if you want a reliable comparative MC measurement.Maybe I am misunderstanding this, but I thought Specific Gravity for timber was the density at 12% moisture content. O'course, I don't know what the moisture content is, which is why I bought the meter. If I just measure the straight up density of any given piece then that will be giving false readings won't it? (because the MC could be anything).

[BobL]

Maybe I am misunderstanding this, but I thought Specific Gravity for timber was the density at 12% moisture content. O'course, I don't know what the moisture content is, which is why I bought the meter. If I just measure the straight up density of any given piece then that will be giving false readings won't it? (because the MC could be anything).

Specific gravity at 12% is only what what moisture meters use but that won't necessarily be the SG or densities available our presented in books or tables. The likelihood of the SG for your piece of timber at 12% being the same as that of the what's in a book is only approximate. That's why using the density method only ever give approximate results. Accurate MC measurements calibrate the meter output direct to an absolute moisture content for a specific timber which of course has to be measured by drying a range of pieces of timber and measuring their moisture loss with a with a balance. This takes lots of time and effort which is why its only been done for a few meters and for a few timbers.

[FenceFurniture]

Yes I understand that even a particular piece of timber can vary (just like the grain does) and that it's only approximate, which is why 10-15% is the desired range (and preferably a little lower up here in the drier climate - no rusty tools here man!). This meter (https://www.wagnermeters.com/shop/orion-930-dual/) comes with a calibration device which is a piece of plastic on 25mm legs complete with serial number to match this particular meter.

However, I'd still like to be able to create a list of SGs in Excel to put in the phone as a PDF to use with the meter when I'm either purchasing timber or evaluating my own stash for "ready to use". Too many shrunken disasters tearing themselves apart when I thought the timber "probably/likely" dry enough, even after more than 1 year per inch.

[BobL]

Have you seen this.
http://www.tocact.org.au/wp-content/uploads/2016/09/Timberspeciesandproperties.pdf

[ian]

Maybe I am misunderstanding this, but I thought Specific Gravity for timber was the density at 12% moisture content. O'course, I don't know what the moisture content is, which is why I bought the meter. If I just measure the straight up density of any given piece then that will be giving false readings won't it? (because the MC could be anything).
Brett
Don't let your OCD get the better of you.

I have a much older version of what I think you have bought -- you have just purchased a pinless Wagner meter?
BTW, Chris Becksvoort uses a meter which uses pins and says you can always find places to hide the pin holes, and failing hiding them, a little water will make them disappear.


If timber in your stash has been drying for a while, what you're really looking for is the variation in moisture content between boards and along individual boards. If you are looking at a selection of Jarrah boards (0.75 SG in Wagner's species table) what you want to know is how the moisture varies along a board and between boards. As long as it's pretty uniform, it doesn't really matter what the "actual" value is.

If your timber is fresh sawn -- i.e. green -- you can still measure the moisture, but just let it dry a little longer.

[FenceFurniture]

Brett
Don't let your OCD get the better of you.

I have a much older version of what I think you have bought -- you have just purchased a pinless Wagner meter?
This meter (https://www.wagnermeters.com/shop/orion-930-dual/) comes with a calibration device which is a piece of plastic on 25mm legs complete with serial number to match this particular meter.Yes, a pinless Wagner, with dual depth reading which should be very useful (6mm, 18mm readings)



BTW, Chris Becksvoort uses a meter which uses pins and says you can always find places to hide the pin holes, and failing hiding them, a little water will make them disappear. With this meter I can just move it over the board and the reading continually changes - very, very fast to assess a board. That is not possible with pins (unless you subsequently run it through the thicky, which is probably likely - not very welcome in a timber yard though...)

[Fekit]

I looked into this quite a while ago. I concluded that there isn't a complete list.

Bobs pdf,
Wood properties and uses of Australian timbers | Business Queensland (https://www.business.qld.gov.au/industries/farms-fishing-forestry/forests-wood/properties-timbers)
Australian timbers volume 1, by Ashley J Sewell

That's about all I'm aware of, hope it helps a bit.

[ian]

Hi Brett

looking at the Wagner species list, I see
Douglas Fir (known in Aus as Oregon) -- 0.48
Gum, Black (US generic term for Eucalypti spicies) -- 0.50
Gum, Red (ditto) -- 0.52
Jacaranda -- 0.34
Jarrah -- 0.75
Jelutong -- 0.38
Karri -- 0.79
Merbau -- 0.67
Mountain Ash (Eucalyptusspp.) -- 0.62 (marketed as Tassie Oak?)
Myrtle, Tasmanian -- 0.64
Pine, Hoop -- 0.44
Radiata Pine -- 0.45
Rubberwood -- 0.51
Sapele -- 0.60
Sassafras -- 0.46


then there's other [to the US] exotics, like

Red Mallee (Eucalyptus oleosa and E. socialis), Average dry weight (1,050 kg/m3), SG (basic 0.79, at 12% moisture content 1.05)
Queensland Maple (Flindersia spp. (F. brayleyana), Average dry weight (560 kg/m3), SG (basic 0.45, at 12% MC 0.56)

etc
Look here Browse by Common Name | The Wood Database (https://www.wood-database.com/common-name/) for more "exotic" species

[FenceFurniture]

Thanks chaps. In the absence of a copiable list, my accomplice (i.e. co-owner) :ninja: is going to create a simple spreadsheet from his timber book of Aust species.

[ian]

Brett
How many different species do you have in your stash?

I'm thinking no more than about a dozen that are not also common in the US, Europe, South America, Asia or Africa and therefore listed on Wagner's species list.

so looking up a dozen "exotics" shouldn't be too difficult

[FenceFurniture]

How many different species do you have in your stash? I'm not sure - quite a few, but not too many by now that should need measuring. It's more about being prepared for whatever might come along, particularly when out purchasing, on a trip etc. Not a particularly onerous task to get the data from the book into an iPad apparently. Having a simple PDF in the phone will be pretty useful I reckon.

BTW, don't forget I have that FRG board here for you.

[ian]

Brett
thanks for looking after the FRG for me


To contribute to your requested list

Mountain Ash, Victorian Ash (Eucalyptus regnans) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 680 kg/m3) -- SG (Basic 0.49 -- 12% MC 0.68)
(https://www.wood-database.com/wood-articles/specific-gravity/)
Beefwood (Grevillea striata) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 965 kg/m3 -- Specific Gravity (Basic 0.78 -- 12% MC 0.96) (https://www.wood-database.com/wood-articles/specific-gravity/)

Bendee (Acacia catenulata) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 1,200 kg/m3) -- Specific Gravity (12% MC 1.2) (https://www.wood-database.com/wood-articles/specific-gravity/)

Australian blackwood, Tasmanian blackwood, Acacia blackwood (Acacia melanoxylon) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 640 kg/m3 -- Specific Gravity (Basic 0.54 -- 12% MC 0.64) (https://www.wood-database.com/wood-articles/specific-gravity/)

Red Bloodwood (Corymbia gummifera) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 865 kg/m3 -- Specific Gravity (Basic 0.70 -- 12% MC 0.87)

Grey Box, White Box (https://www.wood-database.com/wood-articles/specific-gravity/) (Eucalyptus moluccana (syn. E. hemiphloia)) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 1,120 kg/m3 -- Specific Gravity (Basic 0.83 -- 12% MC 1.12)

(https://www.wood-database.com/wood-articles/specific-gravity/)Yellow Box (Eucalyptus melliodora) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 1,075 kg/m3 -- Specific Gravity (Basic 0.81 -- 12% MC 1.08)
(https://www.wood-database.com/wood-articles/specific-gravity/)
Brigalow, orkor (Acacia harpophylla) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 950 kg/m3 -- Specific gravity (12% MC 0.95)
Comments: Brigalow is not commercially harvested, but hobbyists and other craft mills may utilize this wood on a limited basis. Brigalow trees are most closely related to the smaller gidgee (Acacia cambagei) (https://www.wood-database.com/gidgee/)—though the latter’s wood is slightly more dense.

Australian Buloke, Bulloak (Allocasuarina luehmannii) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 1,110 kg/m3 -- Specific Gravity (Basic 0.86 -- 12% MC 1.11)

(https://www.wood-database.com/wood-articles/specific-gravity/)Australian Red Cedar, Toona (Toona ciliata (syn. Cedrela toona)) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 485 kg/m3 -- Specific Gravity (Basic 0.40 -- 12% MC 0.49)
(https://www.wood-database.com/wood-articles/specific-gravity/)
Chinaberry (Melia azedarach) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 610 kg/m3) -- Specific Gravity (Basic 0.47 -- 12% MC 0.61)

(https://www.wood-database.com/wood-articles/specific-gravity/)Cooba, willow wattle (Acacia salicina) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 690 kg/m3) -- Specific Gravity at 12% MC 0.69

River cooba, shoestring acacia (Acacia stenophylla) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 735 kg/m3) -- Specific Gravity at 12% MC 0.74
Comments: A small to medium sized tree, river cooba grows slightly larger than the closely related cooba (Acacia salicina) (https://www.wood-database.com/cooba/). Both yield attractive timber of moderate density (for Acacia) that’s easy to work.

Coolibah, Coolibah burl (Eucalyptus coolabah, Eucalyptus microtheca) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 1,085 kg/m3 -- Specific Gravity (Basic 0.81 -- 12% MC 1.09) (https://www.wood-database.com/wood-articles/specific-gravity/)

Creekline miniritchie, red mulga (Acacia cyperophylla) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 1,100 kg/m3) -- Specific Gravity at 12% MC 1.10
Comments: Sometimes called red mulga for its distinctive red bark, this small tree yields a dense, dark-colored timber. Due to its small size, the wood is limited to speciality and craft uses such as turned objects.

Curracabah, early-flowering black wattle (Acacia leiocalyx) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 850 kg/m3 -- Specific Gravity at 12% MC 0.85
Comments: A small tree with fairly dense, dark-colored wood. Another very closely related species, Acacia concurrens, also goes by the name curracabah. Curracabah is not available commercially and its used is primarily limited to hobbyist and other small specialty craft items.

Australian Cypress, White Cypress Pine (Callitris columellaris (= C. glaucophylla)) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 650 kg/m3 -- Specific Gravity (Basic 0.56 -- 12% MC 0.65) (https://www.wood-database.com/wood-articles/specific-gravity/)

[ian]

and then there's

Huon Pine (Lagarostrobos franklinii) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 560 kg/m3 -- Specific Gravity (Basic 0.47 -- 12% MC 0.56)

(https://www.wood-database.com/wood-articles/specific-gravity/)

[rustynail]

Hi Brett, The AUSTRALIAN TIMBER HANDBOOK by Norman.K.Wallis will answer all your questions. This is the Bible among the old Aussie timber men. Talks in density rather than SG but it is easy enough to crunch the numbers if you want to be pedantic. Remember this is not an exact science and there are variables tree to tree.
Hope this helps.

[FenceFurniture]

Thanks Ken. I understand it's inexact, and not being pedantic - just want to use the meter as it's supposed to be used. Variations are within each board let alone tree to tree.

[FenceFurniture]

Mountain Ash, Victorian Ash (Eucalyptus regnans) -- Average Dried Weight: (https://www.wood-database.com/wood-articles/average-dried-weight/) 680 kg/m3) -- SG (Basic 0.49 -- 12% MC 0.68) (https://www.wood-database.com/wood-articles/specific-gravity/)
Basic 0.49, and 12%MC 0.68. Presumably basic is at 0%MC? Can that ever be the case?

[ian]

Basic 0.49, and 12%MC 0.68. Presumably basic is at 0%MC? Can that ever be the case?
yep
when the sample is oven dried the moisture content approaches 0. I won't claim it gets to zero as I don't know for sure, but oven drying will pretty much desiccate the wood sample.

[ian]

Hi Brett (and your partner in "crime")

attached is an expanded species setting list for your "new" moisture meter

The table is colour coded.
Black text is data drawn from the Wood database
Blue is direct from Wagner's species setting table.

[FenceFurniture]

Hi Brett (and your partner in "crime")

attached is an expanded species setting list for your "new" moisture meter

The table is colour coded.
Black text is data drawn from the Wood database
Blue is direct from Wagner's species setting table.Did you compile that yourself Ian?

[ian]

Yes, I did.
Blue text is the data in Wagner's Species setting table. (A bit of copy and paste followed by search and replace converted Wagner's PDF into a word document)
Black text is data extracted from the Wood Database.

I have two additions for you


New Guinea Walnut
scientific name (Dracontomelon mangiferum)
SG at 12% MC 0.62
SG (basic) 0.50
Average dry (12% MC) density 625 (Wood Database)


New Guinea Rosewood,
Solomon Islands Rosewood
scientific name (Pterocarpus Indicus)
SG at 12% MC 0.65

Average dry (12% MC) density 650 (Britton Timbers)

[FenceFurniture]

Wow, that's damned decent of you! Thanks very much for that. Is it in Excel by chance?

[ian]

You want my Excel spreadsheet ??
Colour coded PDF not good enough?

Yes, the data is stored in Excel.

Given you are proposing to load the data onto a smartphone I thought a PDF would be most useful. If you need the data just ask.

[FenceFurniture]

You want my Excel spreadsheet ?? If you need the data just ask.Ooh, yes please! It means it can be easily updated from this end, and I can prioritise likely species to the top (which saves scrolling through on the phone). Then I'll create another PDF.

[Fekit]

Very decent of you to provide that data ian. Thanks.

476835

[BobL]

Have you seen this post
https://www.woodworkforums.com/f11/wood-moisture-meters-calibrated-australian-species-235112#post2191880

If your meter is mentioned in the list in that post then there is reference to document to about a dozen common Australian timbers that enables accurate MC measurement that does not need density. All it requires is look up table that converts meter reading to real MC. The look up tables are provided in the document.

If you cannot find the document send me a PM.

At a bare minimum you can at least use a species for which an MC look up table is provided to check what you are doing.

Cheers

[ian]

Ooh, yes please! It means it can be easily updated from this end, and I can prioritise likely species to the top (which saves scrolling through on the phone). Then I'll create another PDF.
Hi Brett

Here you go.
I've added a few more species using the Business Queensland site -- see the web links in the comment column.


Note that some of the values in the Wagner Species Table appear not to be an exact juxtaposition of the 12% MC values extracted from other sites such as the Wood Database.

[FenceFurniture]

Cracker, thanks Ian.

[Bushmiller]

Brett

Bootle's book (Wood in Australia) has specs for a many Aussie timbers and also exotics. I think I have another source too. I will have a look when back home.

Not sure if it has aready been mentioned, but meters are calibrated for Douglas Fir (Oregon) and a compensator has to be applied for each species. Correction tables are usually suppied with the meters, but may not cover a wide range of Aussie trees.

Regards
Paul







i

[FenceFurniture]

So after a little massage to suit the purpose, the spreadsheet looks like the attached. Actually two sheets in it - the first one (abbreviated) will go in the phone as a PDF.

Thanks to Ian for the hard yards!

I tell you what - this process has highlighted just how bloody useless common names are (IanW would be having a fit!). Have a look at the Wattles section - There are 3 Black Wattles - all different spp, then there is Early Black Wattle, Early-Flowering BW, Northern BW (ok, reasonable) and I'll bet there are a whole bunch more. Two Purple Gidgees too.

[ian]

I tell you what - this process has highlighted just how bloody useless common names are (IanW would be having a fit!). Have a look at the Wattles section - There are 3 Black Wattles - all different spp, then there is Early Black Wattle, Early-Flowering BW, Northern BW (ok, reasonable) and I'll bet there are a whole bunch more. Two Purple Gidgees too.
Brett
Did you note that there are three (yes THREE) timbers marketed as "padauk" all with different SG settings 0.57, 0.71, 0.79, though the last two belong to the same species.

[FenceFurniture]

Brett
Did you note that there are three (yes THREE) timbers marketed as "padauk" all with different SG settings 0.57, 0.71, 0.79, though the last two belong to the same species.Yes I did. I think I saw about 7 Aussie timbers in the Wagner list, and all of them had different SGs to your source material (some significantly different).

[FenceFurniture]

Have you seen this.
http://www.tocact.org.au/wp-content/uploads/2016/09/Timberspeciesandproperties.pdfThanks for this Bob - very useful. Added 33 species to Ian's list from Wood Database.

Bushmiller has also emailed me an extensive list to sort through - thanks Paul!

It brings up a discussion point though - some of the SGs in that list are quite different to the same species in the Wood Database list. Given that the whole moisture measuring thing is reasonably vague anyway (10-15% is in usable range), at what point should disparities become problematic?

I'm assuming (possibly incorrectly) that moisture measuring is mathematically lineal, and that a difference of 10% in SG will make a difference of 10% in the moisture measurement reading -
i.e. timber with 0.9 SG would read 10% MC different to timber with 1.0 SG, so where one would read 12% MC the other would read 13.2% (without recalibrating the meter) which is not significantly different for these purposes.

That would mean that anything up to ±0.25 difference in SG will make ±2.5% to the MC reading - that should still be more or less in range shouldn't it? A ±0.25 difference in SG would certainly cover all the anomalies that I have come across so far. (I think the biggest was 0.16)


BTW, something I haven't made clear about this meter - and which may be very different to other pinless meters - there is a calibration factor built into it - you enter the SG of the timber into the meter and then take a reading which means there is no need to do a conversion of the reading afterwards.

[ian]

Thanks for this Bob - very useful. Added 33 species to Ian's list from Wood Database.

Bushmiller has also emailed me an extensive list to sort through - thanks Paul!

It brings up a discussion point though - some of the SGs in that list are quite different to the same species in the Wood Database list. Given that the whole moisture measuring thing is reasonably vague anyway (10-15% is in usable range), at what point should disparities become problematic?

I'm assuming (possibly incorrectly) that moisture measuring is mathematically lineal, and that a difference of 10% in SG will make a difference of 10% in the moisture measurement reading -
i.e. timber with 0.9 SG would read 10% MC different to timber with 1.0 SG, so where one would read 12% MC the other would read 13.2% (without recalibrating the meter) which is not significantly different for these purposes.

That would mean that anything up to ±0.25 difference in SG will make ±2.5% to the MC reading - that should still be more or less in range shouldn't it? A ±0.25 difference in SG would certainly cover all the anomalies that I have come across so far. (I think the biggest was 0.16)
OK, so now we are getting serious

From the adjustment information that accompanies another of Wagner's moisture meters

Commentary on Species Adjustment Tables

In 1992, a study was conducted at the Forest Research Laboratory of Oregon State University on species correction for the Wagner Hand-Held Moisture Meters. The species tested were Douglas Fir, Lodgepole Pine, Western Red Cedar, Western Hemlock, White Fir, Western Larch, Engelmann Spruce, and White Oak. Three to four 40-piece samples of each species were tested. Specific gravity was found to be the primary factor on species adjustment. A species equation as a function of specific gravity and the meter reading was obtained using multiple-regression technique
(R-square = 0.95) as follows:

AF = 8.77 + (0.25 * MM) - (15.86 * SG) - (0.62 * SG * MM)

in which:
AF = Adjustment Factor
MM = Meter Reading
SG = Species average Specific Gravity in oven dry weight and 12% moisture-content volume basis.

The species adjustments provide the adjusted moisture measurements that are based on the species adjustment determined using the species adjustment equation, with rounding to the nearest 0.5

Wood is not a uniform material. Specific gravity of solid-sawn lumber varies within the piece and among pieces. In the OSU study, the average specific gravity for each species differed from the individual sample by plus or minus 1% to plus or minus 8%. For general applications, average specific gravity values can be found in the Wood Handbook (USDA Agriculture Handbook No. 72, 1999). Except for one species for which the experimental value is 7% higher, the species’ overall average specific gravity values obtained in the OSU study are comparable with those in the Wood Handbook. The exception may be caused by unknown biases in the sampling scheme. The Wood Handbook values are used in the tables, except for the imported species, unless otherwise noted.

Species adjustment can be determined for lumber sorted, or otherwise known, to have specific gravity different from the species’ average. One example is lumber graded under the Dense rules. If the specific gravity of a lumber sample is known, species adjustment can be determined by the species adjustment equation.

The species adjustment equation provides a way to expand the use of your Wagner HandHeld Moisture Meter for lumber of any species groups having similar species-specific gravity values. One example is Hem-Fir. For a species group, one way to determine the species adjustment is by the use of a weighted average of the individual species’ average specific gravity values. The weighing procedure used in the ASTM D2555 by standing timber volume can be used. Species adjustment is not recommended for any species group having a broad range of species-specific gravity values. There are no recognized limits on species group species adjustment. Species adjustment for species groups should be used with knowledge on the variability on species involved and the affect of it on species adjustment. If the species mix in the lumber production of a species group is controlled or known to have specific gravity different from that used for the species group, a better estimation of species adjustment can be determined using the known specific gravity in the above species correction equation.

I'll post more later

[FenceFurniture]

Many of those species sound like they could be similar to Douglas Fir, in that there is a big difference between the soft rings and the hard rings (I just forget the name for it now). Most noticeable in fast growth trees where the rings are not as tight. Presumably there is a difference in the densities of the two types as well.

[ian]

These numerical values are for a different Wagner moisture meter, but I believe that the table is still useful.

At some stage -- perhaps tomorrow, perhaps much later -- I'll attempt to follow through the comparison formula I posted above.

[FenceFurniture]

These numerical values are for a different Wagner moisture meter, but I believe that the table is still useful.Ian, don't think there's any need for you to go to any trouble for the meter that I have - there are no conversions necessary to be done.

[FenceFurniture]

I have now combined those three sources (Ian's Wood Database, Bob's Forest Industries, Paul's Bootle sheets) into one spreadsheet, attached. Also attached are the two PDFs for my phone, which may be useful to someone. The PDFs are the "abbreviated" versions: Common name, Botanical name, SG @ 12%.

I'm sure there are more to be added, but only if they are likely to be come across in Oz. My version of "Probable or possible" may not suit everyone of course.....you are very welcome to manipulate the spreadsheet and print some PDFs.

[GraemeCook]

Bet you didn't realise how difficult this task would be when you started, FF. Just to complicate your task I will throw in a few more issues.

Geographic variation: A prime timber in Tasmania is celery top pine (Phyllocladus asplenifolius) which Bootles ascribes a dry density of 650. That is applicable for CTP harvested almost anywhere except the Southern Forests (behind Geeveston) where the timber has visibly closer grain, is noticably heavier with density above 700 and feels different - it "rings" if hit with a hammer.

Provinence variability: Plantation timbers are almost always significantly lighter than bush-grown timber, although standard references almost never mention this factor. I will illustrate this by reference to Tasmanian bluegum (E globulus) and by using hardness janka as a proxy for density as I do not have the latter figures:

Old growth - janka 12,
Re-growth - 10.5,
Plantation - 7 - 7.5.


Never tested: A much loved craft timber in Tasmania is horizontal (Anodopetalum biglandulosum). After 20+ years of searching without results I must conclude that no one has ever actually measured its specification.

[rustynail]

The moister meter is not definitive. There are way to many variables for it to be so. I have been using them for as long as they have been available and still find a rap of the knuckle of my index finger on a piece of wood will give a good indication of wet or dry. When supplying timber for the building of the New Parliament House it became evident that not all moister meters were the same or read the same. This caused much delay on the project while an attempt to reach consensus of opinion was undertaken. Indicative would be my approach.

[FenceFurniture]

Bet you didn't realise how difficult this task would be when you started, FF.Actually I was aware of the inexact science involved, and all the vagaries of regional difference, plantation differences etc. I also knew I was going to massage whatever it was that came up.




It brings up a discussion point though - some of the SGs in that list are quite different to the same species in the Wood Database list. Given that the whole moisture measuring thing is reasonably vague anyway (10-15% is in the usable range), at what point should disparities become problematic?

I'm assuming (possibly incorrectly) that moisture measuring is mathematically lineal, and that a difference of 10% in SG will make a difference of 10% in the moisture measurement reading - i.e. timber with 0.9 SG would read 10% MC different to timber with 1.0 SG, so where one would read 12% MC the other would read 13.2% (without recalibrating the meter) which is not significantly different for these purposes.

That would mean that anything up to ±0.25 difference in SG will make ±2.5% to the MC reading - that should still be more or less in range shouldn't it? A ±0.25 difference in SG would certainly cover all the anomalies that I have come across so far. (I think the biggest was 0.16)



In the absence of comments on my theory in post #34 I'll have to assume it is reasonable logic.

[Bushmiller]

Brett

I don't have all my data to hand at the moment, but my initial comment would be to look at the moisture correction tables I sent to you. While I appreciate your meter relies on the density of the timber (albeit expressed as SG, which I find unusual in itself) and does not require correction tables, you will note that the corrections themselves are not linear. Neither do timbers of similar densities have the same correction factor.

All I would say without delving deeply into the figures is that an indicated MC of 12% will probably be around 10% to 15% for any timber (that is a wild guess as it could be 8% to 20%) and the real question is whether that is suitable for the area where you live. If timber is dried down below the equilibrium MC it will rebsorb moisture to the humidty conditons of where you live, although this may take a few weeks to happen. In times gone by, floorbords were only temporarily layed down for this reason and then permanently fixed some weeks later.

One shortcoming I see with your meter (of which I am completely unfamiliar ) is that you need to know what timber you are measuring and know the density or be able to accurately weigh a sample piece to ascertain the density, although when I think on it all meters have an inherent failing in this regard.

I believe the only truly accurate way of meauring MC is the oven dry method, but perhaps others closely connected with the industry can comment.

Regards
Paul

[FenceFurniture]

Paul, as I understand it (wrt timber), Specific Gravity = Density at 12%MC so the SG for a piece of timber at any MC is still xx, whereas the density is whatever it is at the current MC. I may well be confused though. In other words the SG is the baseline for each species to work from.

Following on from that I would have thought that the correction tables issued with meters will do the same correction as changed the SG within my meter.

For the oven dry method: I don't know exactly how it works but it sounds like a sample piece is put in an oven at about 100° until it stops losing weight, and then use the weights before and after drying to work out the MC?

[rustynail]

The test should be conducted at 103C with a variable of plus or minus 2C.

[FenceFurniture]

Yesterday I went to Mathew's Timber and bought some laminated ¼sawn Vic Ash 285x38mm for a desk I'm going to build. Not being in the habit of having a Moisture Meter.....I only remembered it when I was too far from home to turn around. :doh:Well, I figured that buying commercially available timber wasn't going to be too much of a risk.

I measured the MC just now, using a SG of 0.68 and at 19mm & 6mm depth they are reading around 7.5-9% which seems pretty low to me. I would have though they might spend less time in the kiln rather than more? Perhaps it's the case that they'd rather sell the timber with no more realistic shrinkage, only possibly a slight expansion? Maybe Ken might have a comment on that?

I'm pretty confident in the timber - after all, these would be sold to joineries making benchtops etc, so I doubt they should give me problems.

[rustynail]

Timbers like vic ash and tas oak are usually dried to below EMC. They are then reconditioned to the required EMC, usually by steam. Alternatively, they are sold prior to reconditioning and complete the process naturally in there new home - a much slower process. All done in the pursuit of stability.

[Bushmiller]

Yesterday I went to Mathew's Timber and bought some laminated ¼sawn Vic Ash 285x38mm for a desk I'm going to build. Not being in the habit of having a Moisture Meter.....I only remembered it when I was too far from home to turn around. :doh:Well, I figured that buying commercially available timber wasn't going to be too much of a risk.

I measured the MC just now, using a SG of 0.68 and at 19mm & 6mm depth they are reading around 7.5-9% which seems pretty low to me. I would have though they might spend less time in the kiln rather than more? Perhaps it's the case that they'd rather sell the timber with no more realistic shrinkage, only possibly a slight expansion? Maybe Ken might have a comment on that?

I'm pretty confident in the timber - after all, these would be sold to joineries making benchtops etc, so I doubt they should give me problems.

Brett

"Victorian" Ash is a little like "Tasmanian" Oak and is a marketing term for a group of species as no such tree exists with that name.. Victorian Ash can be either Alpine Ash or Mountain Ash with densities of 620Kg and 680Kg respectively. I don't know if the manufacturer would use only a single species for laminating purposes. I would hazard a guess that they would try to use one or the other in any given product. Either way the density you have used may be distorting the result.

Try 620Kg (.62) and see if that results in more as you would expect. It also highlights the difference a variation in density makes.

In fact Victorian Ash is similar to Tasmanian Oak in that two of the species are the same with Tassy oak including Messmate Stringybark as the third timber. I just looked up the difference and Victorian Ash is when the timber is sourced, not surprisingly, from Victoria. :) It is as I said a marketing strategy.

Regards
Paul

[FenceFurniture]

Thanks Ken. At least my thinking was more or less on track.


Try 620Kg (.62) and see if that results in more as you would expect. It also highlights the difference a variation in density makes.lI will, but I expect that will make a difference of around +0.75% (aka not much). I base that forecast on an email I got back from Wagner USA when I queried how to measure for SG >1.0 (because that's where the meter finishes).

They said to just subtract 1.5% MC for an extra 0.1 SG, so where I would read say 12% with SG 1.0, if the timber is 1.1 the reading manually converts to 10.5%.

Therefore a SG difference of 0.06, or close enough to half of 0.1 should mean an adjustment of about 0.75%. Will report back after readings.