View Full Version : Ebay strikes again
Bigwol
29-09-2009, 10:07 PM
I made the mistake of looking around eBay last week, and put in a silly bid for a W T Avery Balance which took my fancy. It turned up today.
It's a bit bigger than I had imagined, but is a thing of beauty complete with knife edge bearings. shining in gold lacquer on solid Brass
I'm going to make it a home on the shelf, but I'll need to raise the shelf above it by a couple of inches to make it fit. You think you've got your bench all tidy and then eBay sends more toys - Still, I'm sure it will come in handy.
http://img.photobucket.com/albums/v470/DaveWallisPics/balance/Balance.jpg
bustagasket
29-09-2009, 10:13 PM
very pretty!!!
snow_imp
30-09-2009, 07:40 AM
Wow, I've never seen anything like it! And I can see why you bought it.
MuranoSilver
30-09-2009, 09:14 AM
Oooh it's like "Steampunk" weighing!! :Y:
Pandanimal
30-09-2009, 09:31 AM
very pretty.
But its not just for looking at is it?
agent_44
30-09-2009, 09:31 AM
Yeah, very pretty, but do you plan on using it?
Bigwol
30-09-2009, 11:14 AM
Yeah, very pretty, but do you plan on using it?
I certainly do - I found it as a result of reading the new edition of Gemstones of the World by Walter Schumann (ISBN 1-4027-4016-6)
Reading the section on Density and Specific Gravity, it explained the Hydrostatic balance method of determining the density of an unknown stone
Weight in air minus weight in water = volume
followed by
Weight in air divided by volume = density
The only straightforward way of weighing the stone in water involved using a traditional balance and a beaker of water - hence the original eBay search which turned up this splendid piece of kit for the princely sum of £14.50!
I'll let you know how I get on - trials scheduled for the weekend :-)
agent_44
30-09-2009, 11:15 AM
Wow!!! Well, have fun with it, let us know how you get on!
EmmaRose
30-09-2009, 02:02 PM
Lovely scales...can you tell what the stone is then, when you have the density?
Em
Bigwol
30-09-2009, 04:49 PM
Yes
On Page 28 of the Gemstones of the World, there is a table Selected Gemstones Ordered by Density, which combined with what the stone looks like (and what you bought it as!) should give a pretty good idea of what it is, though I'm not an expert in it and would seek further advice if unsure.
Cheers
Dave
Ominicci
30-09-2009, 11:27 PM
That is definitely one piece of pretty kit and doubly so at that price!!! Glad you are going to keep it on display too.
Bigwol
02-10-2009, 01:12 AM
The first trials of the new balance appear to be a success.
Though I'm not sure I would routinely use this method, it was worth doing just to see if the theory was borne out in practice.
I chose a Topaz teardrop stone weighing 0.58 grams, which may have been a bit light to start with - nevertheless, it worked OK. Here's how . .
I set up the Balance without anything on it
http://img.photobucket.com/albums/v470/DaveWallisPics/Density/InBalanceWithoutStone.jpg
Made a net to hold the stone
http://img.photobucket.com/albums/v470/DaveWallisPics/Density/Net.jpg
Weighed the stone on its own 0.58g
And the dry net with supporting hook 0.28 and a bit (flickered between 0.28 and 0.29) - decided 0.285 was fair!
I set up the balance with a bridge over the left hand pan, and placed a beaker of water on the bridge, then set up the stone in its net so that the stone was immersed in water
http://img.photobucket.com/albums/v470/DaveWallisPics/Density/StoneInWaterBeforeBalance.jpg
This caused the balance to fall to the side with the stone, so I added casting grain to the right hand pan to bring the scales back into balance
http://img.photobucket.com/albums/v470/DaveWallisPics/Density/GrainNeededToBalance.jpg
Then weighed the grain 0.7 g
Note - This includes the weight of the net which needs to be subtracted to give the net (no pun intended) weight of the stone in water.
The calculations are as below
A Weight of stone in air 0.58 g
Total weight in water 0.7 g
minus weight of net 0.285 g
B Weight of stone in water 0.415 g
A - B = Volume of stone 0.165
Weight in air 0.58 g
divided by volume 0.165 cm3
gives density 3.515 g/cm3
Topaz is listed as being between 3.49 and 3.57 grams per cubic centimetre
Job done - But probably easier finding a gemstone dealer you can trust in the first place . .
snow_imp
02-10-2009, 08:27 AM
Wow - the maths involved in that!
Is that chemistry or physics? 'cos I've never studied either.
:dontknow:
Kalorlo
02-10-2009, 09:09 AM
That would be physics - it's a version of the Archimedes in the bath principle :)
MuranoSilver
02-10-2009, 09:22 AM
Love you're having fun with your new scales :)
The only thing going in my bath at the moment is bubbles....
Feel free to send me Topaz and Diamonds to bathe in though :D
Nic xx
snow_imp
02-10-2009, 09:32 AM
That would be physics - it's a version of the Archimedes in the bath principle :)
Thanks - its always helpful to know new things. :)
Mila Jewellery
02-11-2009, 10:38 PM
Bigwol - I'm curious, what do you use the slow cooker for in your workshop..?
Ominicci
03-11-2009, 09:05 AM
Ha Ha Mila...we've just had a discussion about slow cookers elsewhere in the last few days...it's for pickle probably!
lesley
03-11-2009, 10:28 AM
Fascinating......and one handsome piece of kit.
Mila Jewellery
03-11-2009, 05:18 PM
Ha Ha Mila...we've just had a discussion about slow cookers elsewhere in the last few days...it's for pickle probably!
lol ah pardon my late arrival! I wondered if it was for pickle - brill idea for larger pieces :Y:
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