Author Topic: OE Atribution Help  (Read 767 times)

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Offline hunter-g

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Re: OE Atribution Help
« Reply #10 on: May 02, 2013, 10:30:52 PM »
I certainly agree, Alan, that there's very little to suggest anything more than a basic similarity between this and definitive Bacchus canes. I've reviewed everything I can get my hands on, and never yet a direct match. (Same with the PWT Related Sugar Bowl Trinket / Powder Box I posted a few days back). "Unidentified" or Richardsons suits me fine, as there's little doubt it's OE, and I love the rather delicate work. The cyan is probably my favorite color too as far as glass goes. Really quite an electric blue, and very similar to a beautiful tobacco jar I have with the overlay cut to clear. (Different animal, but number one in my cabinet - outside of weights, of course.)

The question of SG seems interesting, and would warrant another go so the accuracy can be guaranteed, though I'm quite confident of my method - I was very careful.  I'll forward info if/when I can revisit it. I really appreciate your help and reference photos. And btw/ I have indeed seen a number of Richardsons'-type canes where the white is similarly translucent - I musta had my blinders on earlier :) or selective memory loss. Purely a matter of convenience, either way...

Many thanks,
'til next time,
Bruce / h-g


Offline tropdevin

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Re: OE Atribution Help
« Reply #11 on: May 03, 2013, 07:26:28 AM »
***
Hi Bruce.  Accuracy / repeatability is a key aspect of any measurement.  And here is a word of caution for anyone making SG measurements: the margin of error depends very much on the scales you use, and whether you work in grams or pounds and ounces.  That is because the scales round the measurements to a nearest figure (whether the nearest gram, half ounce, quarter ounce etc).

To illustrate: suppose you have a typical OE paperweight, weighing 660 grams / 1 lb 7 ounces.  If it is of lead crystal, and the actual SG is 3.000, then the weight in water will be 440 grams / 15 1/2 ounces.

What results might you get, using typical electronic kitchen scales that measure +/- 1 gram?  The answer is between 2.977 and 3.023.  Using my cantilever arrangement to magnify the effective weight by about 3 times, I would get a result between 2.992 and 3.008.

For pounds and ounces, the answer is far from encouraging. If the scales measure to the nearest 1/2 ounce, the spread of results will be from 2.765 to 3.286! That is so large as to be of little use.  If you can get to the nearest 1/4 ounce, it is not quite so large a spread ( 2.848 to 3.159), but still too large to be of much use in distinguishing makers.

Conclusion - you need to be working in grams, with scales that measure to +/- 1 gram.

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 KevinH

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Re: OE Atribution Help
« Reply #12 on: May 03, 2013, 10:11:18 AM »
Quote
I determined the volume of the PWT by displacement

Quote
The question of SG seems interesting, and would warrant another go so the accuracy can be guaranteed, though I'm quite confident of my method - I was very careful.

I would be interested to know about the actual method used to determine the volume by displacement. Was this done with a scientifically calibrated measuring beaker? Or was it done by measuring the displaced liquid as an overflow from a "full" container? If the latter method was used, how were factors such as liquid surface tension accounted for?
KevinH


Offline hunter-g

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Re: OE Atribution Help
« Reply #13 on: May 03, 2013, 01:22:24 PM »
Good Morning, Alan and Kevin,
I'll describe my process, which was really quite simple. I began with measuring off a quantity of water with a calibrated photographic beaker (CC's / US Fl Oz) and taking a temperature reading since I know temp will affect density. Photography conveniently had me accustomed to working w/ 20 Degrees C / 68F, which is right where I was (and s/b as a "standard" for referencing SG, as I found in several articles online, just to be sure). So, I placed the weight upside down in a small stainless steel pot and proceeded to add the water while keeping track of the quantity just as a matter of course, until the weight was completely submerged. Although this quantity is essentially immaterial, it came out to be 825 cc's. This also allowed the PWT to be at the same temperature as the water after a few minutes rest, since it was very close to begin with (within a degree - ambient air temp).

With a permanent blue marker, I began placing dots down the inside of the pot until I finally touched the surface of the water, at which point the ink immediately flared and created a perfectly level / straight line at the boundary of the water. So as to not disturb this neat little indicator, I tilted the pot with the handle so the water level fell safely away from it then retrieved the weight, ensuring that my fingers wouldn't displace the water near the line, and gently shook of any excess back into the pot as I returned it to level. Other than damp fingers, essentially none lost.

From this point, I simply added water from the calibrated beaker to the pot until the level reached the line, and recorded the amount needed to replace the amount which the Weight had occupied. That volume was 299 cc's.

Not knowing the actual weight of my subject was the next problem. My scale only goes to 600 grams. I phoned my local pharmacy and soon arrived to have them weigh it. No go, since their digital scale only went to a few hundred grams. Same deal w/ 2 local jewellers, but I found 3 shops who advertise wanting to buy gold, and was able to get tenth-of-a gram accuracy from 2 and dwt from the other: (882.2, 881.8 and by conversion 881.78 which averages 881.92 g.) I figured it was important to get at least 3 readings since one never knows how accurate their scales are, ie, trust but verify... and taking the average as a matter of best practice.

Now, simply creating a ratio of the weight in grams over the displacement / volume (also in grams since cc water @ 20C = grams) 881.92 / 299 yields 2.9496. Figuring also that my potential for error in measuring the displaced water was somewhere about a half cc at worst, and knowing that if anything, my reading was higher, not lower (yes, Kevin, due to that pesky surface tension of the water not creating a perfect plane in the graduate), I subtracted 1/2 cc and refigured: 881.92 / 298.5 = 2.9545 SG. And confident that I'm well within a half of a percent of accuracy. The smile grew large as I realized that it was right near the low end of your observed Bacchus SG's, and I'm also accepting that there's a chance that my error may be larger, but as stated above, if anything, my figure for displacement would be high, so reducing it would only increase the SG, and move it more into range... everything else I can be 99.999% sure of.

So, there's my story. Kitchen Science at its best! :) With a little patience and care, I'm sure it's repeatable, and might afford others something to go on, especially if they've got a proper scale to work with. I believe it is about as straightforward as can be, since the objective is to know the volume of the PWT and then compare it to its mass (weight). Empirically measuring the difference in weights in air & water I'm sure works fine too, though somehow to me at least, seems a step removed from simplicity. But if it is a more accurate method, I'd be inclined to stick with it too. Of course, being able to do BOTH tests should only improve the confidence beyond any doubt, since they're taking different paths to the same result.

This is fascinating stuff and nice to dust off the cobwebs for a change! Thanks. Maybe there's still a chance I've got an "unknown Bacchus" after all? Wake me when it's over...

Bruce / h-g


Offline tropdevin

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Re: OE Atribution Help
« Reply #14 on: May 03, 2013, 02:26:33 PM »
***

Hi Bruce.

Your approach would appear to leave relatively little uncertainty in the measurement: an error of 1 cc in volume either way would put the SG in the range 2.935 to 2.955.  But Bacchus is not the only possibility in that range - I have measured a few other OE paperweights that had SG in the 2.93 to 2.96 range, such as the two shown below. The first one is a member of the 'OE 1' Group that I have written about, from an unknown maker.  The other is very neat, but there is nothing that ties it in to Bacchus.

One has to remember that there were probably 30 or 40 glass factories in and around Birmingham and Stourbridge in the mid to late 19th century that might have made 'Old English' paperweights, and we know very little about the output of most of them.

Alan
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"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 hunter-g

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Re: OE Atribution Help
« Reply #15 on: May 04, 2013, 06:00:45 PM »
Beautiful weights, Alan! Regardless of who made them. Of course it would be wonderful if any info on those lost factories ever turns up, and gives us a name or two from so many... At least it's nice to know this is likely a relative. Many thanks again to all for your thoughts & help!
B / h-g


 



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