Author Topic: Late Clichy paperweight with laurel branches???  (Read 2710 times)

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Offline toedeloe

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Re: Late Clichy paperweight with laurel branches???
« Reply #20 on: May 04, 2007, 05:48:30 PM »
Thanks Kev for the pictures of you rig, it seems easy to use, i will try to replicate it.

Thanks Wuff for the input, with the help of the rig i will be able to measure the density of all of my Val Saint Lambert paperweights.

Best regards, Eddy


Offline Derek

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Re: Late Clichy paperweight with laurel branches???
« Reply #21 on: May 04, 2007, 08:06:56 PM »
Hi Eddy

The picture of the rig was my rig (Derek) not Kev's  !!! - I dont know what he uses.

Best regards

Derek


Offline tropdevin

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Re: Late Clichy paperweight with laurel branches???
« Reply #22 on: May 04, 2007, 09:33:18 PM »
Hi Eddy.  Interesting weight and results. I understand how you are estimating the specific gravity, but I think there is a risk of significant experimental error - however, maybe you have tested the same weight several times using your method, and knows how large or small that is.

I carry out specific gravity measurements using the weight in air / weight in water method, using a pivot / beam / knife edge / and electronic kitchen scales (similar to the setup Derek uses).  I measure the paperweight in air, then without changing any aspect of the measuring system, I bring up a container holding water from below, to immerse the paperweight. Those are the only two measurements you need.  I have discussed in detail the various experimental measurement sensitivities in an article in the recently published PCA Bulletin 2007.  Apart from accuracy and repeatability of the equipment, the next most important thing is to work at constant temperature - the water and weight need to be at the same temperature (for example, 20 deg C).  Water purity is of very little importance.

I have measured over 150 Old English weights, but have not measured any VSL or Clichy yet - I will do so in due course.

Alan
Alan
"Better to remain silent and be thought a fool than to speak out and remove all doubt."  Abraham Lincoln.

The comments in this posting reflect the opinion of the author, Alan Thornton, and not that of the owners, administrators or moderators of this board. Comments are copyright Alan Thornton.
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Offline Wuff

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Determining specific gravity
« Reply #23 on: May 04, 2007, 10:05:48 PM »
Let me try to describe my method for the determination of specific gravity ("density").

I started out with a kitchen scale and a measurement beaker: measure the weight of the paperweight, the weight of the beaker filled with water to a given level, and finally the beaker with the paperweight immersed (making sure the water level is the same!). Basic arithmetics will then give you the volume and the specific gravity of the paperweight in question.
Advantage: no sling, also a volume determination.
Problem: determine (reproduce) the exact water level.

To overcome the problem I modified a surgical device (used to suck off liquid during an operation):
(click on images for larger views)
Because of the small diameter of the tube the total volume (water or water plus paperweight) can be reproduced with great precision. Great care has to be taken, however, to avoid air bubbles in the water: this is the same for the method described above - but the jar needs to be emptied/refilled each time - less time to just let it settle down. The other limitation is the display resolution of the kitchen scale, which is not "magnified" as with the "lever principle".
Wolf Seelentag, St.Gallen
Interested in any aspect of Scottish glass? Have a look at Scotland's Glass.


 

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