It’s quite easy to get become blinded by diamond’s brilliance and luster. The customer’s eyes are always glued to the shop windows when they pass by the jewelry shops. It’s impossible to resist the temptation to enjoy the dazzle and rays of sunlight however even diamond’s brilliance can be deceptive. Many retailers sometimes aspire very hard to rather sell their jewelry which can be of lower quality that they claimed than to strive for customer’s interests. They don’t care about it, this is the customer who should. That is why we hope this piece of information will be useful to you in case you are deciding on buying diamond jewelry:
Surface coating is the oldest diamond treatment known to man. It can be traced all the way back to the Georgian period. Surface coating is used for enhancing a diamond’s color and can raise the color by six to seven grades.
Surface coating was originally performed by applying colored tinfoil to the back surfaces of diamonds and gemstones that were mounted in the form of closed-back settings. However, exposure to moisture often caused the foil to wear out or flake away. This was observed when stones were examined through magnification. Some methods of surface coating on diamonds utilized nail varnish and felt-tip pens. This type of surface coating is usually seen in antique pieces. The presence of foil backings does not devalue heirlooms or antique jewellery.
Throughout the years, many other methods of surface coating have been developed. Violet-blue dyes and films are applied to the girdle or pavilion of yellow diamonds. The color violet is used because yellow and violet are opposite each other on the color wheel, thereby cancelling each other out and giving the diamond a whiter appearance. Dye can be removed by immersing the stone in water or alcohol, while sulphuric acid can be used to strip off film.
A primary indicator of film application on a diamond is the presence of trapped air bubbles, which can be seen under high magnification. Another form of surface coating is utilized to make a diamond simulant more similar in appearance to a natural diamond. This is accomplished by applying a thin film of laboratory-grown diamond to the simulant’s surface, therefore increasing the simulant’s overall thermal conductivity and durability.
Any diamond that has undergone any form of surface coating must be disclosed when submitted for diamond grading and diamond certification at a gemological laboratory.
Surface coating on diamonds is considered a fairly durable treatment. All colors can be used in the process, even shades of pinks and blue. Conversely, an off-color diamond can be treated with surface coating in order to produce a colorless diamond.
Despite the durability of the process of surface coating, evidence of the treatment can still be found in the facet junctions of the stone; specifically on the pavilion facets.
The process of surface coating began in order to meet the demand for colored diamonds, which could not be otherwise obtained, unless paid for at a very steep price. Thus, the process of surface coating was instigated. Compared to diamonds that are naturally colored, diamonds that have undergone the process of surface coating can sell for a fraction of the price one would have to pay for naturally colored diamonds.
When purchasing diamonds that have undergone surface coating, it is important to find out what type of treatment has been used. There is a type of surface coating called the infusion technique, which does not color the diamonds permanently. Here, the surface coating is only applied to the pavilion.
On the other hand, irradiation techniques, HPHT annealing and coloring processes that are a combination of both, result in permanent coloration of the diamonds. Diamonds that have undergone these surface coating treatments are considerably more expensive than those that make use of other methods, because the quality of coloration is superior.
In recent years surface coating treatments for diamonds has been an important issue among jewelers. This applies in particular to diamonds of melee sizes. While there are tests that gemologists can conduct to determine whether or not surface coating has been conducted on a diamond (e.g. boiling in sulphuric acid), this is not a practical option for small diamonds, since it can be a very costly process.
A more economical solution to find out whether or not a diamond has undergone surface coating is to use a high quality carbide scriber. The carbide scriber works by revealing scratches on the pavilion facets, the crown facets or both. The carbide scriber method saves time and is quite simple. Colorless diamonds are examined in a slightly different manner–if no evidence of coating is found via the carbide scriber, the girdle is examined under magnification. If brush strokes are found around the girdle, then the diamond has undergone surface coating.
The information is taken from http://www.ideamarketers.com/?Diamond_Treatments_Surface_Coating&articleid=3050097&from=PROFILE