| In the business of buying and selling | | | | All agreed that the color appearance of |
| precious stones there are a number of | | | | rubies and blue sapphires changes in the |
| little tricks picked up along the way, | | | | course of a day, and all specified what |
| tricks that often make the difference | | | | times those stones look best/worst. But, |
| between profit and loss. Collectively, | | | | to the authors' astonishment, there was |
| we might call them "experience," for | | | | no consensus as to what those times are. |
| that is normally how they are acquired | | | | This was all the more interesting in |
| and the price is, usually, high. | | | | that a few stated that they try to |
| "Experience" of this sort is not found | | | | coordinate their buying/ selling of |
| in gemological texts; it comes only | | | | these stones with the time of day in |
| through hard knocks - i.e., buying | | | | which the color appearance was best (= |
| stones from someone who has a bigger box | | | | selling) or worst (= buying). |
| of experience than your own - or, via a | | | | Spurred on by curiosity, the authors and |
| bit of friendly advice passed on by one | | | | two other AIGS staff carried out their |
| who has been there before. Most dealers | | | | own experiments. A selection of rubies |
| have a collection of this "experience," | | | | and blue sapphires of mixed "type |
| kept in a box at the back of the safe or | | | | categories" (see Sersen, 1988) was |
| in some dusty drawer. It amounts to the | | | | periodically examined for two weeks. |
| small pile of gems which are unsalable; | | | | North and east window lighting was used. |
| the gems you have learned valuable | | | | Weather conditions during this period |
| lessons by buying. In other words, gems | | | | ranged from bright and sunny to dark and |
| you should not have bought in the first | | | | rainy. The purpose of these experiments |
| place. | | | | was, of course, to see if the stones |
| One bit of experience that every stone | | | | would change at all in color appearance. |
| dealer worth his rocks soon acquires is | | | | |
| that a stone's appearance is not | | | | The gems were viewed four times daily. |
| constant. Instead, it can and often does | | | | Hue, lightness and saturation was |
| change with the quality of light under | | | | recorded on each occasion, together with |
| which it is viewed. And a change in | | | | respective weather conditions. These |
| color appearance often means a change in | | | | notations were based strictly on visual |
| value. | | | | observation. No conclusive results were |
| In the days before electric light | | | | had, possibly because no comparison |
| sources, traders could only view their | | | | reference was used; only the testers' |
| prospective purchases under natural | | | | memories were involved, just like with |
| light or by the light of a candle. | | | | most dealers. |
| Natural light means direct sunlight and | | | | Now more curious than ever, the authors |
| skylight (light coming from all | | | | took a formal written survey of 20 |
| directions of the sky except directly | | | | colored-stone traders in order to |
| from the sun). | | | | compare their answers and see what |
| Some dealers would examine a stone at | | | | patterns, if any, might emerge. |
| various times of the day, realizing that | | | | The questions asked concerned the |
| the position of the sun in the sky, | | | | lighting conditions used for buying and |
| together with weather conditions, | | | | selling, whether rubies/blue sapphires |
| affected overall color appearance; | | | | change color appearance at different |
| others took it one step further, viewing | | | | times of the day (and if so, when do |
| the gem in sunlight, skylight and in the | | | | they look best/worst) and specifically |
| shade of a tree in order to get an idea | | | | what factors are thought responsible for |
| of how it would look in any lighting | | | | color appearance changes when such |
| situation. Similar practices continue to | | | | changes are seen. |
| this day, despite the availability of | | | | All 20 traders were interviewed in |
| artificial lights of various kinds. | | | | Bangkok. They consisted of 9 Thais, 6 |
| So, why examine gems under natural | | | | Americans, 3 Burmese, 1 Canadian and 1 |
| light, the quality of which is subject | | | | Malaysian. The majority are local |
| to a myriad of changing weather | | | | wholesalers and sales personnel for |
| conditions, when our Modern Age offers | | | | local wholesalers. The others consist of |
| us incandescent and fluorescent | | | | Thailand-based brokers and |
| (including simulated daylight) lighting? | | | | overseas-based dealers who buy in |
| For that matter, why bother to view a | | | | Thailand and/or Sri Lanka and sell in |
| gem under more than one light source, be | | | | Europe and/or America. The trade |
| it natural outdoor light at a given | | | | experience of those questioned ranged |
| time(s) of the day vs. the stone's | | | | from 2 to 50 years, with most having at |
| appearance in the shade, or in | | | | least 10 years experience. Every attempt |
| fluorescent simulated daylight vs. | | | | was made not to phrase questions in a |
| incandescent lighting? The answers to | | | | leading way. People were simply asked |
| those questions lie in whether you are | | | | questions and encouraged to "talk on" |
| an astute buyer or seller, and in what | | | | for as long as they wanted, without |
| part of the world you happen to be | | | | prejudicing comments from the |
| conducting business. | | | | interviewer. |
| "One bit of experience that every stone | | | | "All agreed that the color appearance of |
| dealer worth his rocks soon acquires is | | | | rubies and blue sapphires changes in the |
| that a stone's appearance is not | | | | course of a day, and all specified what |
| constant. Instead, it can and often does | | | | times those stones look best/worst. But, |
| change with the quality of light under | | | | to the authors' astonishment, there was |
| which it is viewed. And a change in | | | | no consensus as to what those times |
| color appearance often means a change in | | | | are." |
| value." | | | | Survey results |
| Viewing gems under natural light | | | | What lighting do you use when buying |
| As in other parts of the world, it is | | | | stones? |
| common practice in Thailand for dealers | | | | Most people (75%) said they buy ruby and |
| and professional buyers to view colored | | | | sapphire after examining those stones |
| stones at a table situated at a window. | | | | under natural skylight only. Of those, |
| Natural light is the accepted lighting | | | | seven people prefer north or northwest |
| "standard," some dealers and buyers | | | | skylight, seven use any direction of |
| preferring north skylight only. | | | | skylight, one specified north or south |
| In the days before the GIA Diamondlite, | | | | skylight and one south skylight only. Of |
| such was also the case internationally | | | | the remaining 20%, one buys only after |
| with the color grading of diamonds. | | | | viewing each stone under north skylight |
| Writing in 1916, Frank B. Wade notes in | | | | and direct sunlight; one uses north |
| his classic volume on diamonds: | | | | skylight or a "daylight lamp"; two view |
| "In the first place see that you have a | | | | their prospective purchases under |
| good north light, unobstructed by | | | | multiple natural and artificial lighting |
| buildings or other objects. There must | | | | conditions; one said he buys using |
| not be any coloured surface near by to | | | | "whatever lighting arrangement happens |
| reflect tinted light, as a false | | | | to be available." |
| estimate might easily result."In the | | | | Lighting used when selling stones? |
| second place, do not attempt to judge | | | | The majority (55%) of those questioned |
| stones at all closely except in the | | | | said they use skylight for selling as |
| middle of the day, say between 10 A.M. | | | | well as buying. Several stated |
| and 2 P.M. Very erroneous results may | | | | categorically that the color appearance |
| easily be had by neglecting this | | | | of rubies and sapphires changes with the |
| precaution."Dark or dull days should be | | | | time of day and they therefore prefer to |
| avoided also. One must have plenty of | | | | buy in "bad light" and sell in "good |
| good neutral light to make fine | | | | light." The rational behind this is that |
| comparisons." | | | | if the stone appears reasonably nice |
| What Mr. Wade has to say about north | | | | under less complimentary lighting, it |
| light and (especially) weather | | | | will look good under any (natural) |
| conditions is echoed by many local | | | | lighting. Selling in "good light" means |
| colored-stone traders today. However, | | | | exactly what it implies: during times |
| the authors of this article were | | | | when natural lighting conditions make |
| particularly struck by the comment | | | | the gem look best. |
| "between 10 A.M. and 2 P.M." as it is | | | | One dealer said he buys in Sri Lanka |
| reminiscent of remarks heard in Thailand | | | | using only northwest skylight, and sells |
| and Burma about rubies and blue | | | | in his U.S. office under quartz halogen |
| sapphires looking "better" or "worse" at | | | | lighting. Another stated she buys rubies |
| different times of day. | | | | under north skylight, but prefers |
| So, wondered the authors, does the | | | | selling them under "direct sunlight in |
| quality of natural light vary enough to | | | | the afternoon, because the light is |
| cause noticeable differences in the | | | | yellow." In both instances, the lighting |
| appearance of rubies and blue sapphires | | | | used for selling is perceived as |
| at different times? Not only had Bangkok | | | | complimentary to the gem's color |
| dealers mentioned this before, but some | | | | appearance. |
| had gone so far as to say that they | | | | The rest largely buy in skylight and |
| regulate their buying and selling | | | | sell in whatever lighting is available |
| according to the time of day and weather | | | | or under lighting conditions expressly |
| conditions. | | | | requested by a customer, such as |
| It was decided to telephone a few local | | | | skylight from a particular window |
| colored-stone dealers, all of whom have | | | | direction. Obviously, dealers who do all |
| been in the trade for years, and ask | | | | their buying and selling from one office |
| them the following questions: | | | | location have more control over lighting |
| Do rubies and/or blue sapphires change | | | | conditions than does a broker who must |
| appearance at different times of the | | | | sell - and accept consignments - under |
| day?If yes, when do rubies look better | | | | whatever lighting is available, natural |
| worse? When do blue sapphires look | | | | or artificial. |
| better/worse? | | | | |