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| Testing Specific Gravity http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10101&t=30974 |
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| Author: | Mitch Johnson [ Thu Feb 03, 2011 5:27 pm ] |
| Post subject: | Testing Specific Gravity |
How many of you out there test your tops for specific gravity. Is it a waste of time or does it yield some useful info? What are your methods if you do? I was shown a way to do it and I know it's done in the violin world sometimes. Just curious if anyone's doing it. |
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| Author: | Ti-Roux [ Thu Feb 03, 2011 5:47 pm ] |
| Post subject: | Re: Testing Specific Gravity |
It's pretty simple, and you can find density and humidity level at the same time. Take a scrap that comes from your top. Take the precise volume Witdh x lenght x height. Mesure the weight. Then cook the piece to dry it completly, and mesure it again. |
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| Author: | Alain Moisan [ Thu Feb 03, 2011 6:53 pm ] |
| Post subject: | Re: Testing Specific Gravity |
Hi Mitch, I'm not sure what you mean by 'gravity'. Could you explain what you have in mind? |
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| Author: | Zach Ehley [ Thu Feb 03, 2011 7:47 pm ] |
| Post subject: | Re: Testing Specific Gravity |
Specific gravity is density with 1 equalling pure water as the reference. Petros has some listed on their site. General numbers at that. http://www.petrosguitars.com/woods.htm |
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| Author: | Alain Moisan [ Thu Feb 03, 2011 10:50 pm ] |
| Post subject: | Re: Testing Specific Gravity |
ok if you see it in the way that specific gravity is another way of expressing density, than yes, many of us care a lot about that. We just tend to stick to the more popular ratio of mass/volume. |
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| Author: | wbergman [ Fri Feb 04, 2011 2:47 pm ] |
| Post subject: | Re: Testing Specific Gravity |
If you do your volume measure in cubic centimeters and your weight in grams, then divide weight by volume, don't you get specific gravity without further conversion? You would do this on the wood as it is, without toasting it. |
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| Author: | Jim Watts [ Fri Feb 04, 2011 2:55 pm ] |
| Post subject: | Re: Testing Specific Gravity |
wbergman wrote: If you do your volume measure in cubic centimeters and your weight in grams, then divide weight by volume, don't you get specific gravity without further conversion? You would do this on the wood as it is, without toasting it. You do if your water density is actually 1, but the density of water varies with temperature, which is why a temperature is required for specific gravity as Todd pointed out. The differnce between g/cc and specific gravity is moot for our work. |
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| Author: | Alain Moisan [ Fri Feb 04, 2011 3:01 pm ] |
| Post subject: | Re: Testing Specific Gravity |
Jim Watts wrote: The differnce between g/cc and specific gravity is moot for our work. I would tend to agree with that. It's not like we're doing nuclear science here... |
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