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Author Topic: Units of Measurement  (Read 3697 times)

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Offline Bernard C

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Units of Measurement
« on: May 20, 2006, 06:11:41 AM »
It seems to me to be reasonable to use as your primary unit of length the unit that was in use by that glassworks at the time, with an alternative measure given in brackets for those of us today who are not used to the system.    So, for example, all British glass other than the most modern should be measured in inches, with a metric measurement given as an alternative if it could be useful to some readers, thus:- 8" (20cm).   This provides the link to measurements in contemporary material such as pattern books, trade catalogues and advertisements.

It also keeps us well away from loony statements like "The Davidson Column Vase was made in three sizes, 15cm, 20cm and 25.5cm", when we all know it wasn't, it was made in 6", 8", and 10" sizes, and only serves to confirm that the writer is very confused, a complete plonker, or (in Britain) a trained archaeologist*, or, quite possibly, all three.

You can go one step further and use italics to show derived lengths rather than measured lengths, so 8" (20cm) would show that the object was measured in metric only, and that the inch measurement was derived.

So, my question is what primary measurement system should I use for Venetian glass dating from c. 1895–1920?    Were the Murano glassworks using the metric system then, or some earlier system?   It seems logical to describe the height of my blue vase as 13.5cm (5¼"), but I could be technically incorrect.

In a more general sense, when did the metric system become widely accepted and used on the European mainland?    ... and what systems did it replace?

Bernard C.  8)

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Offline Della

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Units of Measurement
« Reply #1 on: May 20, 2006, 06:29:44 AM »
Hello Bernard,

I found this:

http://www.unc.edu/~rowlett/units/metric.html

It has some fantastic history about when the metric system was introduced. I am not sure, if they say which system was in place before this time, as I don't have time to read the whole article, as I am in a hurry to get packed etc.
Whilst I am in the UK, I will try to get a tape measure which has inches on it. I only have a cm tape, as that is what is for sale here in The Netherlands. Although, not knowing where a piece originates from, could cause problems for me :oops:
Which unit of measurement do I use first and which do I put in brackets or italics?
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Offline Bernard C

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Units of Measurement
« Reply #2 on: May 20, 2006, 07:13:40 AM »
Quote from: "Deltab"
... Which unit of measurement do I use first and which do I put in brackets or italics?

Always the units that the glass was made in first, with other measures in brackets.

Thanks for the link.   It shows that Italy was fully metric by the time my glass was made, so the height of my blue vase is quite properly given as 13.5cm (5¼") or just 13.5cm.    Note that 13.5cm (5.25") is not correct, as it implies an unwarranted degree of precision, one of the two major problems of the metric system, the other being the relative scarcity of factors of 10 compared to 12.

Bernard C.  8)
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Offline Bernard C

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Units of Measurement
« Reply #3 on: May 20, 2006, 07:58:57 AM »
Oh, and don't take me too seriously.   If you are measuring a piece for IDing, whatever units of measurement suit you.    If you know its origin and age, then it's best to stick to the above guidelines.

Bernard C.  8)
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Offline Glen

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Units of Measurement
« Reply #4 on: May 20, 2006, 08:23:11 AM »
I think there are some other things to consider when giving measurements. Essentially I agree with you Bernard, one should use the units of length given by the manufacturing company.

However, I feel there are circumstances when a conversion is justified. Firstly, if the item(s) in question is already well known and sizes are accepted and in common use. For example, if say, a vase is well known as being a 6" vase - then it seems preferable to me to continue referring to it as such, even though the original maker sized it in centimetres.

Secondly, I think it depends on the "audience". I personally prefer (if am writing for a USA audience) to use the Imperial terms, for items made in mainland Europe. If circumstances warrant it, I would also use the original metric measurement.

Glen
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Offline David Hier

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Units of Measurement
« Reply #5 on: May 20, 2006, 09:48:54 AM »
As Metric is almost universally accepted as the standard form of measurement, most people reading threads in this forum will not be familiar with imperial. That would include almost everyone in Europe and most people in the UK under the age of 40.

For reasons of clarity, I think that metric measurements should be given precedence, with imperial dimensions supplied in brackets.

Not to ignore the measurements originally specified by manufacturers: the original unit of measurement should only be given precedence when referring to advertisements, publications or pattern books that are contemporary to the period when an item was made. In which case, measurements should be quoted from the original documentation and metric (or otherwise) conversions provided afterwards.

If you are not directly quoting from a document, but are still referring to sizes mentioned in a document, these should be stated in inverted commas e.g. "these vases, as mentioned in the original catalogue, were available in '8inch, 10inch and 12inch' heights". You would then provide a metric conversion in brackets.
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Offline Bernard C

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Units of Measurement
« Reply #6 on: May 20, 2006, 10:01:56 AM »
Quote from: "David Hier"
... If you are not directly quoting from a document, but are still referring to sizes mentioned in a document, these should be stated in inverted commas e.g. "these vases, as mentioned in the original catalogue, were available in '8inch, 10inch and 12inch' heights". You would then provide a metric conversion in brackets.

No, David, the three measurements I cited in my original post were sizes, not heights.   The actual measurements vary considerably, depending on whether the rims were flared or turned over (D'ed in Davidson terms).

Citing a metric measurement for a British-made item with an inch measurement in brackets is at best confusing.   We are talking here about marrying primary printed and written source material with actual objects.

I can see that this topic is going to raise some interesting views.   I do enjoy a good debate.

Bernard C.
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Offline David Hier

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Units of Measurement
« Reply #7 on: May 20, 2006, 10:59:31 AM »
Quote from: "Bernard C"
No, David, the three measurements I cited in my original post were sizes, not heights.   The actual measurements vary considerably, depending on whether the rims were flared or turned over (D'ed in Davidson terms).


I wasn't actually referring to your example, but giving an example of how measurements should be dealt with.

As I have already mentioned, when dealing with measuremnts mentioned by the original manufacturer, the original units should be given precedence. However metric conversions should be provided, so that those who do not understand imperial units can get an idea of the sizes being discussed.

If you refer to the size of a vase being 6" in a pattern book and supplement this with a size in cm (15.2), I can't see how that could be confusing. The sizes are equal to one another. Besides, if someone only has metric measuring devices, they will need conversions to compare dimensions with items they own.

In all other instances, such as describing a piece of glass for identification, metric units should be used, with imperial sizes given in brackets.
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Offline Frank

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Units of Measurement
« Reply #8 on: May 20, 2006, 11:56:36 AM »
Most people do use the metric system today so it becomes a historical quirk to continue with imperial as the main measurement. From the start ysartglass has used both units throughout. With a childhood based on the imperial system, I can only estimate in imperial but always convert to metric when communicating. My son in the UK, now in his 30's has no idea what an inch is. I struggle with temperatures though, I can never remember what is normal in  centigrade (an archaic term used by imperialists for Celsius).

However in old catalogues it is still common to find other types of units in use and these are not always easy to interpret.

I keep next to my monitor a list of conversions, for my site, from imperial fractional inches to millimeters and I always round to the nearest 5mm. Of course accuracy is irrelevant with Monart where an inch of variation can be found in most size codes in practise. Some old catalogues also state that measurements given are nominal or approximate.
Frank A.
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Offline David E

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Units of Measurement
« Reply #9 on: May 20, 2006, 12:13:22 PM »
For myself I'm sticking with the imperial measurement as used by Chance at the time: their plates were listed as 8" or 10" for example, or the Posy Vases are recognised as 4", 5", 7" and 8" in height — as Bernard suggests. But I am also using the metric equivalent as a secondary unit: does add more work, but will help Euro visitors, as well as those British 'youngsters' who were bought up with Metric only :)

As with all things, we do tend to 'visualise' our own terms of reference. I can quickly convert from Imperial to Metric, but cannot appreciate the size until it's converted to 'old money'.
David
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