by Professor Gene Wengert
There used to be a supplier in Milwaukee, WI. I'll see if I can find their name.
Professor Gene Wengert is Extension Specialist in Wood Processing at the Department of Forestry, University of Wisconsin-Madison.
Click on Wood Doctor Archives to peruse past answers.
The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).
Comment from contributor A:
In Australian terms, with red cedar it takes about 2.3 kN to imbed the steel ball halfway in, Oregan (Douglas Fir) 3kN, Teak 4.9kN, and jarrah takes 8.5kN. So jarrah compared to those species available in the US is quite hard. Timbers from Outback Australia, however, such as Brigalow (Acacia Harpophyllia), Mulga (Acacia Aneura), Gidgee (Acacia Cambadgei) and Coolibah (Eucalyptus Microtheca) along with others take 17 kiloNewtons to imbed the steel ball to half its depth(that is not a misprint - it is 17 kN). So by comparison, these timbers are 6 times harder than red cedar and Oregan, three and a half times harder than teak and twice as hard as jarrah. Incidentally, they are also extremely strong and very dense (they all have a density greater than 1). They work quite well with modern TCT tools, glue quite well with modern glues and have a beautiful figure (grain). They grow as small trees (typically < 8ft long and 10" dia logs), so therefore only come in small end sections (typically 1 x 2 up to 1 x 6) and up to 8ft long.
Comment from contributor B:
I periodically work jarah. It is common in the New Zealand boatbuilding industry for keel support sections, due to its strength, stability, water and weather resistance. It cuts and machines well with sharp steel tools. If gluing you need an epoxy and sufficient film thickness as not to starve the joint.
Comment from contributor C:
I have worked with jarrah for some time. Here on the southeast coast of England (Brighton), much of it was washed ashore from storms. It was (is) used for sea defense reinforcements and as far as I know, also for the old piers. I was told that it was originally imported to the UK as cobble stones for London. I have various bits of furniture maded from this salvage. It has an interesting reaction from the sea salt/iron bolts, leaving black flames around the bolt holes. It works extremely well (better than oak's twisted fibres), but you need very sharp, high grade tools, otherwise they blunt quickly. The figure can be beautiful indeed.
Comment from contributor D:
On a relatively minor point, the wood is spelled with a double r not a single letter. It's a great timber. I speak as (a) an Australian, and (b) someone who used to run a sawmill in Malaysia.
Comment from contributor E:
I live here in jarrah country. Jarrah is native to the south west corner of Western Australia. It is renowned as being resistant to borers, termites and rot. In the late 1890s some streets in London were paved with jarrah blocks. I am told they are still there under the road and most are still in reasonable condition. It was in great demand for railway sleepers and mine timbers.
When green, it is relatively easy to work, but the older it is, the harder and more difficult it is to work. I am presently building a treehouse for my children from old jarrah. Each nail and screw hole has to be pre-drilled as it splits very easily and is so hard that a nail will often bend before going in half its length. Oiling finished jarrah will improve its appearance and durability. As an aside, I burn it in my stove and it burns very hot, down to large chunks of charcoal with virtually no ash. It is, however, a little difficult to start and needs to be cut relatively small as it is also resistant to fire. Green jarrah sinks like a stone when thrown into water and floats (just) when dry.
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