Author Topic: Late Clichy paperweight with laurel branches???  (Read 2653 times)

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Offline toedeloe

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Re: Late Clichy paperweight with laurel branches???
« Reply #10 on: April 30, 2007, 09:45:48 PM »
addg, i did find the John Hawley article about the specific gravity testing on the internet. Since i do not have the same professional equipment to measure it, the testing has been done in a "kitchen" environment and will be less accurate. The resulting densities are :
- Paperweight with Laurel leaves = 2.49 g/cc (Possible factory according to the tests by John Hawley : Bohemian1, Pantin2, Boston & Sandwich)
- Closepack paperweight = 3.13 g/cc (Possible factory : Clichy, NEGC, St.Mandé, Pantin1, Bohemian2, Bacchus, Boston & Sandwich)
If it is true that the two paperweights are from the same factory , the resulting possible factories are Pantin, Bohemian or Boston and Sandwich.
I am not shure if one can make any conclusions as a result of these figures and also i am not shure the "John Hawley" article is complete since i did not find any figures relating Belgian paperweight s.a. Val Saint Lambert or Cheneé (which also produced low and high density paperweights).

Any advice or suggestions in interpreting these densities would be much appreciated.
Eddy


Offline karelm

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Re: Late Clichy paperweight with laurel branches???
« Reply #11 on: May 01, 2007, 11:58:56 AM »
addg, i did find the John Hawley article about the specific gravity testing on the internet.
Care to share the link?  The only reference I could find was to a 1992 PCA bulletin....if somebody has a scanned copy.....
Thanks,
Karel
"Holy cows make the best steaks"


Offline toedeloe

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Re: Late Clichy paperweight with laurel branches???
« Reply #12 on: May 01, 2007, 03:16:58 PM »
karelm, the link i found is :
http://www.paperweight.org/05_convention/JohnHawley.pdf
Regards, Eddy


Offline KevinH

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Re: Late Clichy paperweight with laurel branches???
« Reply #13 on: May 01, 2007, 10:33:24 PM »
Eddy,

I think it is good that you have gone to the trouble of obtaining density measures of your weights. But could you please let us know how you did this - in other words, what "kitchen" method did you use. I ask because this has often been discussed amongst members of the PCC and, as yet, I have not heard of an agreed "kitchen" method that could be easily used, with a fair degree of accuracy, by other folk.

For my own density measures, which I made using a setup similar to that outlined by John Hawley, I found a variety of discrepancies, not only between results of other people, but also between my own repeated measures of the same weight!

One aspect that could well be important is the temperature of the water. There is a table of adjustment factors that are used by "professionals". When I tested this with the same item, with all other conditions the same, I did get some differing results in the decimal places.

Another factor that is suggested by some folk, is the "purity" of the water. However, I have found no differences when using "pure" water (as sold for use in batteries) and "hard" tap (faucet) water containing loads of chalk, and no doubt other odds and ends too!
KevinH


Offline Derek

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Re: Late Clichy paperweight with laurel branches???
« Reply #14 on: May 02, 2007, 08:51:52 PM »
Hi Kev

For what its worth - here are my experiences. Its a bit long winded !

My rig is based on the one Tropdevin (Alan) uses.

It is based around a beam made from a 24" length of ali - cross-section 2 1/4" x 1/4" . In one end is drilled a hole though which a steel pivot rod passes - the pivot rod is secured via a wooden cage to  the contiboard base.

At the far end of the beam another hole is drilled and through this is suspended a cage made of plastic covered garden wire in which the paperweigt is suspended.

A set of digital kitchen scales sit on the base board and the beam bears down onto the scales though a fulcrum made from a small triangular shaped piece of brass.

I use a LARGE measuring jug for the water - straight sides and about 8" diameter.

Weighing process is as follows :

1) position the rig on the draining board with the suspension point for the PW over the sink . Position the jug of water in the sink under the suspension point.
2) Zero the scales
3) Carefully put the PW in the sling and weigh again - air weight
4) Without moving anything carefully bring the water jug up from the sink until the paperweight is totally immersed. Take a second reading - immersed weight.
5) Lower the water jug and remove the weight. Check that the scales still read zero - if not then do not use this reading as something has moved

I take a series of readings until I get 2 or more identical ones. This is the reading I use - I do not average out. Then perform the calculation.

Points to note.

1) The beam must be rigid with NO flexing under load.

2) Ensure that the fulcrum postion is adjusted so that the air weight is near the maximum for the scales as this will reduce the errors caused by reading the scales. A 1g error on an apparent weight of 1800g is of less concern than a 1g error on an apparent weight of 800g.

3) Some scales only read to 2grams - if the reading flickers beween two readings use the average - eg 860g and 862g use 861g 

4) Put the weight into the cage dome side down - this will prevent an air bubble affecting the readings.

5) Always dry the PW between reading.

I believe the reasons for inconsistant readings are 1 or more of the following :

1) Fulcrum has moved on the scales.
2) Scales have moved on the baseboard
3) Friction at the pivot or cage suspension point.

Points 1 and 2 can be easily overcome by taking several readings
Point 3) cound be cured by better engineering but providing several readings are taking until 2 or more consistant results are achieved then I dont believe it is necessary.

Hope this helps

Regards

Derek


Offline Wuff

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Re: Late Clichy paperweight with laurel branches???
« Reply #15 on: May 02, 2007, 09:38:55 PM »
... i did not find any figures relating Belgian paperweight s.a. Val Saint Lambert or Cheneé
Kulles quotes 3.03 to 3.05 for Val St.Lambert
Wolf Seelentag, St.Gallen
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Offline toedeloe

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Re: Late Clichy paperweight with laurel branches???
« Reply #16 on: May 03, 2007, 08:21:31 PM »
kevH and derek,

Thanks for the inputs, i will explain my humble method :
I take a plastic container and fill it with water in such a way that the paperweight can be fully submerged . I put it on a kitchen scale and set the scale to zero. I then fix the paperweight with a strip of secure tape all around in such a way that a small handle is available to hold the paperweight by hand.
I put the paperweight in the water untill it is just fully submerged and hold it still until the scale reading is stable = immersed weight(1) including tape = W1
Then i drop the paperweight including the tape gently in the water = air weight including tape = W2
Then i measure the paperweight after drying and without tape = air weight = W3
The density will then be calculated as follows : W3 / (W1 - (W2-W3))
I performed this test with a known 'Saint Louis' weight and my findings where : 3.37 g/cc.
According to the predicted 99% range calculated by the "John Hawley" report "Saint Louis" was between 3.20 and 3.41, so my measurement is in the predicted range.
May i suggest you do the measurement as i described and compare it with the method you are using and let me know your findings.

(1) : this immersed weight is not the same as the "water weight" in the "John Hawley" report.

Regards, Eddy


Offline KevinH

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Re: Late Clichy paperweight with laurel branches???
« Reply #17 on: May 03, 2007, 09:59:20 PM »
Thanks Derek & Eddy,

I have a couple of questions, but I need to think about something first.

In the meantime, for Eddy's description, is there a "typo"?
Quote
Then i drop the paperweight including the tape gently in the water = air weight including tape = W2
Air weight measured by dropping the object gently into water?

KevinH


Offline toedeloe

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Re: Late Clichy paperweight with laurel branches???
« Reply #18 on: May 03, 2007, 10:19:49 PM »
Yes KevH, my choice of words was not correct. I meant : "lower the paperweight with the tape gently into the water untill it reaches the bottom".

Sorry for my English, it seems not as good as i thought.
But anyway the result is the same as measuring the "air weight" (including tape)

Regards, Eddy


Offline Derek

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Re: Late Clichy paperweight with laurel branches???
« Reply #19 on: May 04, 2007, 12:00:21 PM »
Hi Kev and Eddi

A picture of my rig is at this link -  http://tinypic.com/view.php?pic=4ytqivs

No water but should illustrate the rig in action. Note how the fulcrum is positioned only 1/3 of the way from the pivot point - effectively increasing the apparent weight of the paperweight 3 times.

Best regards

Derek

 

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