Talk:Troy weight

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In the article it says:

"One cubic inch of distilled water, at 62 °F (17 °C), and at a barometric pressure of 30 inches of mercury, was determined to weigh 252.458 troy grains (gr)."

Which definition of the cubic inch and inch is intended? The inch has changed values considerably throughout history, the latest in 1960 when it was defined as 0.0254 m. This would have noticeable effect on the all of the non-metric units.

Why not make one more change? Define the Troy ounce as 31.25 g exactly. This way there would be 16 ounces in 500 g and 32 in a kilogram. It will also be easier to weigh out troy ounces on a gram scale. —Preceding unsigned comment added by 70.187.73.207 (talk) 17:55, 27 February 2010 (UTC)

I think the paragraph "One cubic inch of distilled water, at 62 °F (17 °C), and at a barometric pressure of 30 inches of mercury, weighs 252.458 troy grains (gr)." needs to be removed from this article, I don't see what it has to do with Troy weight! It's more like the definition of an inch, but as the inch varied until 1958 it does not apply, this particular reference is from 1840.Metricmike (talk) 03:12, 2 October 2011 (UTC)

I removed the offending paragraph. Zyxwv99 (talk) 21:34, 13 November 2011 (UTC)
The variation of the imperial yard, relative to the metre, would vary the metre from Kater's value of 39.37079 inches, to a value closer to 39.370113 inches. The effect on volume is 51 ppm. This would vary, eg 252.458 to 252.471 over the historical era. The actual value of 252.458 was a determination from 1820's sanctioned at law for converting gallons to cubic inches. A new measurement in 1898 gives 1 cu inch as 252.325 grains troy, this is the basis of the modern gallon of 4.54609 cu in.
"grains troy" distinguishes from other grains, like "grains tower", "grains avoirdupoise" (which was proposed but never used), and "baker's grains". The avoirdupoise dram was to be divided into 30 grains avoir, or into 28 grains in Baker's Tables (in notes on rifle guns). Tower grains are 1/640 tower ounce, or 1/682.666 troy ounce. avoirdupoise and tower grains were current when that particular quote was written.
The inch did not so much vary. What happens is that the standard changed relative to the metric one, and that the extent of the variation has little effect except on geodetic surveys, and on making guns. Similar variations exist in metric (german legal metre). Wendy.krieger (talk) 07:34, 11 April 2012 (UTC)

Who defined the grain in terms of the gram? When? -- Anon.

Thomas Corwin Mendenhall. April 5, 1893. See Mendenhall Order Zyxwv99 (talk) 01:53, 21 November 2011 (UTC)
The relationship of 1 pound avoirdepoise is 7000 troy grains, was first a conversion relation between a particular averdepoise and troy scale, and then the definition of the pound, (up to 1834, the standard of weight was two troy pounds), and then the definition of the grain (the new standard was 7000 grains). The definition of the grain in grams was made in 1959 by international agreement that the grain would be 64.7989 or 64.79891 milligs, this half-way between the Seer's 1922 and Broch 1880 determinations. The latter was selected. The US value derives from Broch's determination of the pound in grams. Wendy.krieger (talk) 08:12, 13 April 2012 (UTC)

"ounce of gold weighs more than an ounce of feathers" - be careful with that "weighs" word. Unless you weigh in a vacuum, a gram of gold weighs more than a gram of feathers, too.[1] Kwantus 20:23, 2004 Dec 8 (UTC)

Tried to fix mess. How's it look? Rossumcapek 02:04, 13 Dec 2004 (UTC)

In the troy system, there are 20 pennyweights in an ounce, and 12 ounces in a pound. In pre-decimalisation British currency, there were 20 pence in a shilling, and 12 shillings in a pound. I'm pretty sure there were other currencies with these subdivisions as well. I'm wondering if there's any historical basis for this; if anyone knows, it could make a good addition to the article. Izzycat 23:45, 18 February 2006 (UTC)

British currency was: 4 farthings to a penny; 12 pennies to a shilling; 2 1/2 shillings to a half crown; 5 shillings to crown; 20 shillings to a pound; 21 shillings to a guinea. Easy, huh?

The currency reform of King Offa replaced the scetta with a silver penny, derived by dividing the moslem dirhem into two coins. The resulting coin is about the size of a silver threepence, or about half the size of a dime. The shilling was then set at twelve pence (in place of smaller and larger values), and the pound as twenty shillings. Also, the ounce was set to twenty pence. In this time, and for 300 years there after, a (tower) pound of silver was a currency pound. The first mention of 'troy' in an act was 1309, but elsewhere this is implied as the tower pound (since the 480 grain ounce did not appear until much later). Wendy.krieger (talk) 08:12, 13 April 2012 (UTC)

If troy is a system of mass and avoirdupois is a system of weight (which is what the entries say) there should be a disclaimer somewhere that we're talking about (say) sea level on the earth.

It should be mentioned that troy measures are derived from Troyes, not Troy. I don't have any better sources though than the other Wikipedias (e.g. German and Russian). --Oop 18:33, 11 November 2007 (UTC)

One etymology for 'troy' is the market town in france (troyes). This is the usual etymology given in dicitionaries, but given as tentivite. The actual weight is again based on an moslem gold prototype of 48 grains troy, which may have been traded at troy.

This has to be one of the dumbest suggestions I've heard for the use of "Troy". It came from Troyes in France? WTF? What muppet came up with that? No. Troy comes from the Germanic root of English. Meaning true. A troy pound is a true pound. Germans still use the word today to mean faithful. You can look it up in any German dictionary. — Preceding unsigned comment added by 87.160.169.126 (talk) 12:55, 28 April 2013 (UTC)

However, Colonel Watson "British Weights and Measures" suggests a different etymology (pp 32-33). Having established that the words 'troy' and 'avoirdupois' were in use before their scales, the names could not have followed the weights. Instead, 'troy' relates to dialectic 'troi' balances, and 'avoirdepois' to 'goods of weight'. troy weight is then weights by scales (gold, silver, gems, medicines), while avoirdepois is goods of weight (every thing else).
The original metric system made the distinction between the two kinds of weight (grave avoirdepois vs gram troy), but the intervention of the 'system usuelle' preempted the grave-scale, and by the time it came to eliminate the system usuelle, the notion of dual weights became somewhat dated. That's why we have kilograms instead of graves. Wendy.krieger (talk) 06:44, 12 April 2012 (UTC)

Millesimal fineness[edit]

How does the Troy ounce translate into a millesimal fineness figure? I'm trying to establish if all the 'oz' mentions in 16th century coin were, in fact, referring to Troy ounces. According to John Chown (A History of Money from AD 800, page 43, on Google Books) the 'Troy Pound' replaced the 'Tower Pound' in 1526 as the measurement for the Royal Mint. What I need to know from this article is was the Troy ounce the standard ounce in all money in Tudor England after 1526? Thanks. 86.42.102.87 (talk) 23:52, 16 April 2008 (UTC)

I am assuming you are talking about English coins. While it's not really a source on coins, I think you should read Chapter I.4 of Connor and Simpson: "Weights and Measures in Scotland". This book seems to contain the most correct and up to date information on English measures of the time. In short: English and Scottish measures were essentially the same if you only look at the ounces (not at the number of ounces in a pound), and so far as mint weights are concerned there was only the tower ounce of 450 troy grains (but probably divided in 480 tower grains), superseded by the troy ounce of 480 troy grains. However it seems that the weight of a grain was increased from 64.76 mg to 64.80 mg in the 18th century, as the result of an erroneous decision after the official standard was lost. However, since the error consisted in using the faulty standard that was in use at the mint as the base for the new standard, you should really read the book and the paper Simpson and Connor: "The mass of the English troy pound in the eighteenth century" if you need it as exactly as that. (I am also not sure I am summarising everything correctly, as it's rather late for me.)
I don't see the connection to fineness. I think for silver in this period it was always "sterling", but at the time if they had debased the money by reducing the fineness, the meaning of the word would have been adapted, so I just don't know about that. --Hans Adler (talk) 01:18, 17 April 2008 (UTC)
Fineness for silver was in ounces of 20 dwt, pure = pound. Sterling was 11 oz 2 dwt fineness, or 11.1/12. Purity of gold was in carats of 4 grains, viz pure = 24 carats, 1 carat = 4 grains. The arab dirhem or mitkal weighs 24 carats, as did the solidus at one stage weigh 24 carats. A coin of weight 24 carats would be say, the weight of two dimes (US money), or a nickel. A gold coin would be about the size of a dime (US sixpence). Wendy.krieger (talk) 07:34, 11 April 2012 (UTC)

Scottish system[edit]

We need the absolute weight of one of the scottish units. Rod57 (talk) 03:57, 5 December 2008 (UTC)

For Scottish weight units I recommend "Weights and measures of Scotland" by R.D. Connor, which contains the results of the latest research. It turns out that even before the forced unification the Scottish units weren't so different from the English units. Mostly there were regional units that were different even within Scotland or England, and there were national units that were "originally" (i.e. dating very far back to the time when the large Scottish cities were founded) the same in both countries. The main difference that evolved over the centuries was that different units were lost, e.g. the English stopped using the ell (previously used primarily for measuring goods traded with Germany) and the Scots stopped using the yard (previously used primarily for measuring land). A further complication was that 19th centuries antiquaries sometimes misread the surviving weight and measure standards (e.g. the ell standard), because the tradition how to use them was lost. The book is really amazing – if I remember correctly, Scotland was trading with Venice in the first millennium! --Hans Adler (talk) 11:10, 5 December 2008 (UTC)


The paragraph on the Scottish system is internally inconsistent or at least unclear as it now reads (5/1/10): “Thus there were 16 drops to the troy ounce, 16 ounces to the troy pound, and 16 pounds to the troy stone.” Is the standard reference for the Scottish system the troy ounce (480 grains) or the troy pound (5760 grains)? As written, the Scottish ounce would be 1/16 of a troy pound (360 grains), and the Scottish drop would be 1/16 of troy ounce (30 grains). This would then make the Scottish drop 1/12 of a Scottish ounce (30/360). If so, the Scottish system would then lose the implied symmetry of 1/16 of 1/16 of 1/16 of a “Troy Stone.” [b.t.w., is a troy stone even defined or used elsewhere? And, who would be trading in a mass of a precious metal of that size?] If it were based only on the troy ounce (480 grain) then the Scottish pound would be 16 troy ounces or 7680 grains. If it were based only on the troy pound, the Scottish drop would be 1/16 of 1/16 of a Troy pound or 22.5 grains. In the light of the comment s previously submitted: 01:18, 17 April 2008 (UTC) and 11:10, 5 December 2008 (UTC), it appears that the details of actual historical standards are unclear.

If the facts are so convoluted and unclear, does the full paragraph on Scottish system even belong in the “Troy weights” article? Perhaps the “Troy Weight” article should only make a passing statement such as, “Incorporation of Goldsmiths of the City of Edinburgh used another system. (See the article on the History of Weights & Measures).”

I would ask those with editorial experience to ponder whether the following statement belongs in the “Troy Weights” or “History of Weights and Measures” article: “In Scotland the Incorporation of Goldsmiths of the City of Edinburgh used a system in multiples of sixteen. Sixteen drops to an ounce and sixteen ounces to a pound and sixteen pounds to a stone. It is unclear exactly how the ounces or pounds actually related to pounds and ounces in the Troy system of weighing precious metals.”

The scottish troy pound was 7716 BI grains, but often rounded to 7680 grains. It divides to 16 ounces, of 16 drops of 30 grains, and 16 pounds make a stone. Denominations of weights tend to run to binary powers, which encourages powers of two in weights. Wendy.krieger (talk) 07:52, 13 April 2012 (UTC)

Additionally, before an actual reference is made as to how the Scottish system related to the Troy system, the detail of the primary reference (See Assay-Master's Accounts, 1681–1702, on loan from the Incorporation to the National Archives of Scotland.) should be consulted more precisely. MDB341 15:59, 1 May 2010 (UTC)

I have removed this irrelevant piece:-

Ettin is archaic English for giant, and one wonders whether Edinburgh was so named for an unofficial reputation as the "City of Giants." You can recognize a cognate of ettin in the Icelandic word jötunn, which means giant (Jötunnheim was the realm of the giants in Norse mythology, Old Norse being all but identically the same language as modern Icelandic.) Ceartas 21:03, 9 July 2010 (UTC)

Scottish troy measure is unrelated to either of the English systems. 'troy' as an appellation to a weight system first appeared with the tower system in 1309. The troy oz of 31,104 gramms appeared somewhat later: thus troy can not refer to the town in france, but is a method of weighing of precious things by balance. Wendy.krieger (talk) 06:44, 12 April 2012 (UTC)

Reasons for Continued Use[edit]

I stumbled upon this article while searching for what a Troy Ounce was. One thing I will look into is why the Troy Ounce remains the measure for Gold and other precious medals as opposed to converting to Grams or some other measure. If anyone else has resources or information on this subject I think it would be valuable to the article. Drockel (talk) 19:07, 4 March 2009 (UTC)

This question actually comes up a lot. It's for the same reason that railroad tracks are stuck at a certain gauge. If they wanted to switch to a wider gauge, they'd have to tear up all the railroad tracks in the country and start all over again. It's why my computer still runs on X86 technology, and why the human brain is just a thin layer of mammalian tissue stuck onto a reptile brain. Much of the world's gold supply is in the form of 400 oz. (troy) bars of gold, purity usually 0.995. Much of the gold supply of Asia and parts of Africa is in the form of 22-karat 10-tola bars. The tola is a unit of British India equal to exactly 3/8ths of a British Imperial troy ounce. On the other hand, much of the world's gold supply is also denominated in kilograms. Go to Switzerland and buy some gold bars, they almost all come in metric sizes.
Zyxwv99 (talk) 02:08, 21 November 2011 (UTC)

Troy Weight[edit]

The following moved from User talk:Indefatigable

This system does not measure mass, it measures weight (as the name implies). For example, an item which measures 1 troy ounce on earth will not measure 1 troy ounce on the moon or in free space (because an ounce measures weight). By comparison, 1 gram of a substance will measure 1 gram everywhere in the universe (because it measures mass). —Preceding unsigned comment added by 71.139.9.126 (talk) 22:02, 13 November 2009 (UTC)

Please let's not use the term weight: it's ambiguous. You seem to be contending that troy units measure force, rather than mass. This is incorrect: they are mass units. When these units were invented, the only devices that could measure troy units were balance scales. Balance scales measure mass, not force: they give the same reading regardless of the gravitational field (as long it's not zero). Spring scales for measuring force were not invented until many centuries later. Indefatigable (talk) 22:15, 13 November 2009 (UTC)

Well, it really comes down to whether you think a pound of steel is still a pound of steel on the moon. Physicists would say "no". Apparently you would say "yes". To me, this implies that saying troy weights measure mass is, at least, contoversial (if not ambiguous). —Preceding unsigned comment added by 71.139.16.134 (talk) 16:59, 14 November 2009 (UTC)

If it's a force, how is that force defined? It's easy to see that it's mass by following the chain of definitions. A kilogram is the mass of an artifact in France. An avoirdupois pound is legally defined as 0.45359237 kg. A troy pound is legally defined as 5760/7000 of an avoirdupois pound, so both pounds are legally mass units. I acknowledge that there is also a unit called pound-force, which is usually abbreviated to "pound", but the troy units have never spawned force units. Only the avoirdupois mass units have spawned parallel force units. Indefatigable (talk) 20:13, 14 November 2009 (UTC)
In legal and commercial usage, "weight" means "mass" as physicists understand the term. Zyxwv99 (talk) 21:11, 11 November 2011 (UTC)
Why do we get these people who think that the physics use of 'mass', 'displacement' etc supercede all other uses. In metrology, weight refers to what balances measure. In theory this is moment of force around the fulcrum, but in practice, gravity cancels out, and the balance measures moment of mass. An equal-arm balance has a direct dependence of mass down to eight significant digits. Troy weight is weight by balance is always mass. Wendy.krieger (talk) 07:58, 13 April 2012 (UTC)

This page needs a different picture of a gold or silver bar which actually says TROY ounce on it! —Preceding unsigned comment added by 74.71.117.59 (talk) 07:46, 20 February 2010 (UTC)

There is a picture on the Krugerrand which shows it as being '1 oz', it is not usual to give it as troy. Wendy.krieger (talk) 06:44, 12 April 2012 (UTC)

I looked all over Google Images and couldn't find any. Furthermore, I hadn't even gotten around to narrowing my search to public domain images. Coins, yes, but not bars. Zyxwv99 (talk) 02:14, 21 November 2011 (UTC)
Troy weight is normally implemented by bullion coins. Large weights are usually done in chogs of 32 oz 3 dwt 7 mites troy. Wendy.krieger (talk) 07:58, 13 April 2012 (UTC)
Gold held by central banks is mostly in 400 oz. bars, although in recent decades they've been acquiring more gold denominated in kilograms. This is probably the only reason why the troy system hasn't been discontinued: if it was, central banks would have to melt down trillions of dollars worth of gold and have it re-cast to conform to standard.
The reason I haven't been able to find any photos is not that such bars don't exist or haven't been photographed, but that the word "troy" is nowhere to be seen in the photos. That's because, in the world of gold, "ounce" (or "oz.") is presumed to mean "troy ounce."
Gold traded on commodity exchanges is typically 100 oz. The buyers are the jewelry, electronics, and dental industries, as well as private investors.
As for "chogs of 32 oz 3 dwt 7 mites troy" I've never quite heard of that, although there is something called Mini Gold (33.2 ounces). However, the use of the word "mite" brings up another point: this article fails to mention mint weights. There are 24 blanks to a perit, 20 perits to a droit, 24 droits to a mite, and 20 mites to a grain. These are all part of the troy weight system. Zyxwv99 (talk) 14:17, 14 April 2012 (UTC)
Mint weights: Thanks to User:Zyxwv99 for fixing the {{clarification needed}} and giving them some context. --Old Moonraker (talk) 20:30, 21 April 2012 (UTC)

Watson's conjectures[edit]

Several weeks ago someone added two paragraphs to this article about Watson's theory on the origin of the troy weight system, one in the Etymology section and one in the History section (second paragraph of Origins subsection). At first I thought this was just another alternative theory. However, after the same material appeared in the Grain (unit) article I became concerned and decided to look into it.

British Weights and Measures as described in the laws of England from Anglo-Saxon Times by Colonel Sir C M Watson KCMG, CB, MA, late Royal Engineers, (1910) is a twenty-thousand-word booklet with no footnotes, end notes or bibliography. In the preface, Watson describes it as "popular" clearly in the sense of not claiming to be scholarly. The full text of Watson's book can be found at archive.org The relevant details can be found on pages 32-34.

Watson claims that the word "troy" means "balance" or "scale" (i.e., equal-arm as opposed to auncel scale) and goes back to Old English. (An auncel is a scale with a fixed weight and movable fulcrum.) However, the only evidence he cites is Wright's English Dialect Dictionary. In order for this claim to carry weight, Watson would need to be a credentialed linguist, dig up more evidence, publish the results in a peer-reviewed academic journal, and wait for other linguists to weigh in. Since Watson is not even a linguist, this entire line of argument is mere conjecture.

Next, Watson claims that the word "tron" is a synonym for "troy" and that the tron family of weight systems is an extension of the troy weight systems. As evidence he cites a single instance in which the Public Record Commissioners translated "troni ponderacionem" as "troy weight." The Public Record Commissioners were responsible for compiling statute books and translating old statutes from Latin and Anglo-Norman into modern English. The text in question is from the Assize of Weights and Measures (Tractatus Ponderibus et Mensuris), one of the famous Statutes of uncertain date circa 1266-1304. However, according to the OED the word "troy" in connection to weight is first attested about a century later in 1390. Furthermore, both the tron scale and the tron family of weight systems are well documented and have no connection with troy weights.

Finally, I can find no mention of this theory in the literature, or anywhere for that matter.

Then there is Watson's second theory, described in this article under Origins in the History section, that the troy system may have some connection to Arabic weights, in particular to the 48-grain dirhem (i.e., twice the troy pennyweight in the same way that the 45-grain dirhem is twice the 45-grain dirhem). Watson admits (page 6) that this is a conjecture, his own words being "it is not unreasonable to suppose that there is some connection ." I have seen the same conjecture in various 19th century Google books. Even though I find this conjecture intriguing and would like to see some real evidence to back it up, I have not been able to find any mention of it in reliable contemporary sources.

In conclusion, I feel that the inclusion of Watson's first theory violates WP:FRINGE and should be removed, while mention of the second theory should also be removed on the grounds that Watson's book is an unreliable tertiary source.

Zyxwv99 (talk) 15:22, 11 September 2012 (UTC)

Mint Weights[edit]

The progression of subdivisions makes the smallest, the blank, equal to about 281 nanograms. Yowza! Were these finest of units ever in common use, even by the mint? It seems hard to believe that one could conceive of weighing anything to anywhere near that precision in 1649. Joe Avins (talk) 17:05, 29 May 2013 (UTC)

At the time these units were developed, precision of measurement was progressing by leaps and bounds. They had no idea what kind of precision would be possible in future centuries, but they wanted to be prepared. Kind of like using 4 digits for computer dates instead of 2, or other situations where extra room is left for future possibilities. Even though the smallest mint weights were not in routine use, the standards laboratories that supervised the mints had very advanced technology (for the time) and went to extreme lengths in calibrating their own standards. Zyxwv99 (talk) 01:50, 5 June 2013 (UTC)