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PhilUSAFRet
04-20-2011, 02:47 PM
The lapidary in me has to ask if anyone has ever heard of using this material for nut or bridge? Can be worked with metal working tools, isn't expensive either. It comes in a few colors including shades of green & black. It would seem to be suitable material as long as it is solid material.

Sorry, seems like I may have had serpentine in mind (if you can still call it a mind). Hardness 2.5 to 4
Had black in mind.

chiefnoda
04-20-2011, 03:43 PM
Hi PhilUSAFREt

Soapstone is mostly composed of talc, which is very soft. In Geology, they Mohs Hardness Scale from 1 (softest) to ten (gardest). and talc is 1, the softest on the scale.

For comparison, bone (mostly hydroapatite) is about the hardness of 5. Fingernail is 2.5. Copper is about 3.

My guess is that it takes bone to be a good material and fingernail is not. So soapstone is probably too soft. It may work OK for a nylon string, but against a wound string, it will wear out rather quickly.

I am sure there are other factors for something to be a good nut/saddle material (sound transmission?) but due to the hardness, I don't thnk soapstone is a good material.

On the other hand, what do I know? Maybe you can experiment - soapstone may have really good properties other than hardness and it may prove superior.

Random thoughts from me

Happy Pickin
Chief

bbycrts
04-20-2011, 06:22 PM
I have no qualifications here...but I've carved a couple things in soapstone. I am sure that it is so soft that even nylon strings would eat their way right through it in no time. Any stone that you can correct imperfections in your carving with your fingernails probably isn't suited for this purpose.

UncleElvis
04-20-2011, 07:24 PM
I think African Soapstone is a two, so... yeah... I don't think ANY soapstone is appropriate for a nut or saddle.
I'd be worried that it would just crumble to dust as soon as it starts vibrating.

Now... here's a Q for the luthierly inclined...

Is it hardness that affects transmission of sound? and if so, is it: The harder the better?
And if so, what would a super-hard stone saddle and/or nut do? Something like a 6 or a 7 (or even corundum! OOOH! That's, like, a 9!), I'm talking.

Sorry if this is a derail, but I think the OQ was answered, no?

PhilUSAFRet
04-21-2011, 02:36 AM
Thanks for the feedback. I originally thought of Jade, it's hard enough and tough enough, but a pain. Just wondered. Now I think I may have had serpentine in mind. Hardness 2.5 to 4 and it can be worked with metal working tools.

chiefnoda
04-21-2011, 03:26 AM
Hi

Jade has a Mohs scale of 6.5 so it is hard enough but I have a feeling it's not easy to carve and file. I think the trick is you need something hard (for durability) but not too hard (so you can file and carve).

FYI - this is a decent list of materials and Mohs scale

http://www.jewelry-secrets.com/Other/Whats-The-Mohs-Scale-Of-Hardness/The-Mohs-Scale.html

Happy Pickin
Chief

hoosierhiver
04-21-2011, 04:16 AM
I think I've heard soapstone dust can be harmful if inhaled, so be careful when messing around with it.

maybe try onyx?, it might be e little too hard (6.5 - 7) but could be pretty.

ichadwick
04-21-2011, 04:29 AM
Nuts have little effect on the sound, so really only the hardness is relevant for them.

For a saddle, you have to look into a material's acoustic properties. You have to try to figure out what sort of impedance (the resistance to certain frequencies) and its pass-through (the frequencies that get transmitted to the bridge and then to the top) it has. And a few other things...

Look at the chart here (http://www.efunda.com/materials/common_matl/Common_Matl.cfm?MatlPhase=solid&MatlProp=Acoustic#Acoustic) for some acoustic properties of common materials. The first figure, the longtitudinal velocity is basically the speed of sound in that material (in air it's about 331-350m/sec. So aluminum is much faster - at 6,700 m/sec). If you look at the woods (and here too (http://physics.info/sound/)), you'll see wood is in the 4,000-5,000 m/sec range. Longtitudinal waves are simple compression waves.

The other thing to consider is the elasticity of the material (Young's Modulus (http://www.engineeringtoolbox.com/young-modulus-d_417.html)). The material has to bounce back quickly after compressing, or else it can't transmit the next wave in time. Low elasticity means higher impedance. Rubber is slow, aluminum is fast. But brass is faster - which is in part why it's a good acoustic material. Wood is fairly slow. That means it has more inertia (low elasticity means higher inertia: the material is reluctant to change its state).

Shear waves are transverse waves, moving perpendicular to the longtitudinal waves (they look like the sine wave created in the instrument's string). These are slower, so they don't arrive at the same time as the longtitudinal waves (there are shear waves in solids, but not gases or liquids, by the way). So these create overtones and harmonics, as well as giving some duration to the tones. These waves bounce back (and depend on the elasticity to do so).

And finally there's density. A dense material generally transfers the waves better, faster and with more fidelity than a less dense material. Denser materials can transmit a wider range of frequencies, especially those in the treble range.

Got that? Soapstone (http://www.tulikivi.com/usa-can/fireplaces/Soapstone_Characteristics_Fireplaces) doesn't have the elasticity, but it does have a fair density compared to other stones. However, it also has a high heat absorption capacity with a low dispersal of that heat, which makes me wonder if acoustic energy will be wasted by conversion into mechanical energy. In fact, some builders (http://whittendesigns.com/pdf/tulikivi.pdf) use soapstone because it absorbs sound, rather than reflects it.

So I'd say: try it. If you're looking to make a shrill or bright uke more mellow, it should work. In fact it might make an interesting material for a banjo uke bridge. But because it is soft, it may wear the string slots faster than other materials. I don't think it's the best material, but it's decorative and might be able to modify a sound quite nicely.

chiefnoda
04-21-2011, 05:03 AM
the hardness ... acoustic properties ... impedance ... longtitudinal velocity ... compression waves ... elasticity ... Young's Modulus ... more inertia ... transverse waves ... overtones and harmonics ... density.

Got that?

Oh iChadwick

You're talking dirty. And I love it.

Happy Pickin'
Chief

markyd
04-21-2011, 08:09 AM
I don't want to pick your post apart, but you are confusing several different terms and giving some false information. For example, you imply impedance is the inverse of elasticity (which you imply is equivalent to Young's Modulus), but I believe the modulus is actually equal to the acoustic impedance times the wave velocity. Also, you suggest that "a dense material generally transfers waves...faster", but the first link you submitted clearly shows that is not the case: aluminum velocity is faster than brass, copper, gold, etc, all which are more dense than aluminum. Actually, in general, less dense solids have a higher wave velocity, but the actual relationship is that the modulus divided by the density is equal to the velocity squared.

Everything is inter-related, but most of these characteristics can be roughly described by the modulus and the density, along with the geometry, which makes things frequency dependent.

But in general I would come to the same conclusion: try it and see what happens. In a musical instrument, there is enough variability in materials and geometry that many of these quantitative calculations become almost meaningless.

marky-d

ichadwick
04-22-2011, 02:43 AM
Thanks for the corrections. I may have been confused about the relationship between Young's Modulus and elasticity. My physics classes are a few decades in my past, so when I read this stuff today the neurons might misfire a few times.

Generally it is true that denser materials transer the energy faster - in a coarse appreciation, air is slower than water which is slower than metals. But of course the actual material/molecular structure affects that velocity, so you are correct when appying my comment to specific materials within any group.

Outhouse
04-22-2011, 12:19 PM
Well, the science and techno speak is nice. No offense, I do understand it all. But in practice .....
The nut needs to be just as good as the saddle. The string does vibrate on it and it can have a MAJOR effect on how an unfretted string sounds and it's sustain.
BUT, once fretted, the nut is out of the equation.
That said .....
A great bone substitute is Corian. Yeah, the countertop stuff. Go to a woodworking store and look in the pen turning section. Corian pen blanks come in a variety of colors, swirls etc. A matching nut and saddle is a quick and easy job ... and one blank makes several sets.
Just keep string slots away from the edge .... it will chip or splinter, but I don't see Uke string tension being a problem.

Matt

PhilUSAFRet
04-22-2011, 02:22 PM
Well, the science and techno speak is nice. No offense, I do understand it all. But in practice .....
The nut needs to be just as good as the saddle. The string does vibrate on it and it can have a MAJOR effect on how an unfretted string sounds and it's sustain.
BUT, once fretted, the nut is out of the equation.
That said .....
A great bone substitute is Corian. Yeah, the countertop stuff. Go to a woodworking store and look in the pen turning section. Corian pen blanks come in a variety of colors, swirls etc. A matching nut and saddle is a quick and easy job ... and one blank makes several sets.
Just keep string slots away from the edge .... it will chip or splinter, but I don't see Uke string tension being a problem.

Matt

Great tip for corian source....probably better colors for instrument use than counter top scraps.

ichadwick
04-23-2011, 02:15 AM
A great bone substitute is Corian. Yeah, the countertop stuff.
A while back I was looking into Corian and came across several guitar building sites that discusses its properties. There are quite a few folks in guitarland who think it's inferior to bone, but others defend it. I recall seeing a few graphs of comparison charts with Corian as one of the materials, but been too long for me to remember where. Might have been at the Graphtec (Tusq) site.

I think the onyx suggestion might be worth trying.

Vic D
04-23-2011, 06:31 PM
In my limited experience corian is a tad softer than bone, but works really nice on sopranos. The muliticolored corian isn't as stable as the solid colors, but it sure shines up pretty. I wouldn't use it on a full size guitar though.