Why is koa usually stabilized but walnut often not?

M

milkbaby

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I'm not trying to open up a hoary debate over stabilized versus non-stabilized woods for knife handles, but I am very curious as to why black walnut is often used without stabilization whereas it seems like koa is almost always used stabilized? From the wood database website, it appears the physical characteristics of both woods are almost the same except that koa actually has a more even ratio of tangential to radial shrinkage than walnut!

Is it only because people have found walnut to occasionally turn ugly colors upon stabilization? Or is it just that I personally haven't seen non-stabilized koa handles mentioned as often?

Koa:
Average Dried Weight: 38 lbs/ft3 (610 kg/m3)
Specific Gravity (Basic, 12% MC): .53, .61
Janka Hardness: 1,170 lbf (5,180 N)
Modulus of Rupture: 12,620 lbf/in2 (87.0 MPa)
Elastic Modulus: 1,503,000 lbf/in2 (10.37 GPa)
Crushing Strength: 7,060 lbf/in2 (48.7 MPa)
Shrinkage: Radial: 5.5%, Tangential: 6.2%, Volumetric: 12.4%, T/R Ratio: 1.1

Black walnut:
Average Dried Weight: 38 lbs/ft3 (610 kg/m3)
Specific Gravity (Basic, 12% MC): .51, .61
Janka Hardness: 1,010 lbf (4,490 N)
Modulus of Rupture: 14,600 lbf/in2 (100.7 MPa)
Elastic Modulus: 1,680,000 lbf/in2 (11.59 GPa)
Crushing Strength: 7,580 lbf/in2 (52.3 MPa)
Shrinkage: Radial: 5.5%, Tangential: 7.8%, Volumetric: 12.8%, T/R Ratio: 1.4

???
 
Koa and walnut are mechanically almost identical. That is not the reason. The thing is, there is a lot of koa and a LOT of walnut. Most of it is pretty plain grain that gets used in all manner of things. The figured stuff is the kind of stuff we see. And well figured koa is worth more than well figured walnut, so more people are willing to pay to stabilize it. Unstabilzied koa is just as good as unstabilized walnut. One is just easier to find and less pricy. There are also the issues of walnuts color fading or changing and that some walnut doesnt react well to stabilizing, but generally it is simple economics. People will pay more for a nice block of stab koa than stab walnut. So which do more people choose to stabilize?
 
Could you explain why some walnut is OK with stabilizing and another not OK ? Walnut is found in many environments therefore many weights etc. Learned that in gunsmithing school! . While I have black walnut here ,just down the road there is a stand of a cousin white walnut .Most have never heard of that one and it has very little color !
 
By white walnut I assume you mean butternut, it's a member of the walnut family that tends to be a lot paler, a lot softer and very easy to work.

That is another reason. Walnut is highly variable based on where it free, what species and so on. Koa, while it does have variation tends to be much more homogenous
 
i get both stabilized only due to the fact i get anything that will take the resin stable. im sure i could use both woods withought stabilizing but if im putting it on a handle i want it as durable as it gets. most of my work is kitchen knives and straight razors so my work not only gets used but wet and and washed with soap and water
 
I had about 30 blocks of black walnut stabilized this winter. One difference I notice is it still has fairly large pores compared to stabilised Koa. They don't seem to fill as well when carding as unstabilized but that might just be something I'm doing wrong.
 
mete said:
Could you explain why some walnut is OK with stabilizing and another not OK ? Walnut is found in many environments therefore many weights etc. Learned that in gunsmithing school! . While I have black walnut here ,just down the road there is a stand of a cousin white walnut .Most have never heard of that one and it has very little color !
Click to expand...
Here in Cally we have a white Walnut that produces great eating nuts that's grafted onto a English Walnut stump because it's more big/disease resistant! I've used the English or Stunp wood for handles unstabilized, I was told that it doesn't take the resin well?
 
Koa is mainly found in Hawaii and it harvest and export is closely controlled. most koa lumber comes from trees that were storm damaged or diseased.
 
Curly California Walnut by Robert Erickson, on Flickr

I've had a number of blocks of California Walnut stabilized by K&G and have been pleased with the results. I was able to fill the pores fairly well during finishing. I used a slurry of the walnut sanding swarf and Danish oil to rub into the pores at around the 400 grit stage.
 
That looks nice. Here's the latest one I did, from the batch I had K&G do as well. You can see how the pores didn't fill so well for me. Maybe I just didn't work at it enough. I love the color in all of this that I sent fwiw.

rv4KDC7.jpg
 
We stabilized more than a thousand blocks of walnut. We stabilized claro, english, black and turkish. The only type that consistently failed was frankette walnut. Other than frankette, all the other types stabilized well with only a few problems. I think "walnut failing to stabilize" is overstated.

We stabilized hundreds of blocks of koa. In our testing, the appearance and chatoyance of koa improved when it was professionally stabilized.

Chuck
 
I recently rescued about a dozen or so old walnut stair banisters from an early 1900's house that was being demo'd but really don't have a use for them. I was told by a cabinet maker that they are black walnut. Part of them are turned and part are octagonal. I just didn't want to see that nice old wood go to waste. If anyone would like some, I could cut them into pieces small enough for knife scales so they could be shipped. I would just ask that you reimburse me for shipping. Drop me a PM if you are interested.--KV
 
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