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Embedding

When casting with diamonds it is imperative to use a liquid additive such as "Pro- Tech:D or to coat the tree with a special investment such as "SRS Stonecast". It is important to comply strictly to the manufacturer's mixing instructions.

It is not essential to use additives or special investments for stones such as rubies, sapphires, garnets, tourmaline, etc., although this improves the quality of the casting.

It is not advisable to use these special products which contain boric acid with cubic zirconia stones, as they impair their shine.


De-Waxing

It is advisable to use steam de-waxing before placing the flasks in the burnout oven.


Burnout cycle  for diamonds and emeralds    max. burnout temperature = 630°Ctime 6h    metal casting temperature = 480°C-530°C  for cubic zirconia, rubies, sapphires, garnets and synthetic stones    max. burnout temperature = 680°Ctime 5 h    metal casting temperature = 550°C-600°C
Suitable alloys and casting

Alloys containing de-oxidising agents and with low shrinkage rates are the most suitable. Stone casting with invisible setting can be implemented with silver, yellow-, pink- and white gold in all karats.


Melting and casting method

Melting can be effected with the centrifuge system or with suction/pressure. If melting with palladium white gold it is advisable to use a centrifuge with vacuum and to accurately measure the temperature of the metal. A good melting plant will give a better and, above all, a more constant product quality.

After melting, flasks must be allowed to cool gradually to prevent thermal shock which could ruin the stones.

Flask cooling time:
only diamonds 20 minutes
all other stones 60 -120 minutes
Finishing of cast pieces

Cast pieces may be finished with traditional methods by hand or with automated systems, as long as the compounds and added products are suitable for the hardness of the stones.

Casting tree in gold with invisible setting and some finished rings and bracelet

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The rubber mould

If silicone rubber or caoutchouc are used for hot vulcanisation, all of the model's dimensions must be made about 5% larger to compensate for shrinkage of the rubber.

This is not necessary when using rubbers for cold vulcanisation type RTV silicone, such as the series "Ditto TM Mould compounds"by Rio Grande.

To obtain perfect waxes, it is imperative to make release cuts in the rubber along the comers of the support net.

Cross section of the rubber mould

Injection JWaxes

It is advisable to use elastic or flexible waxes, coloured blue if possible, such as "Plast-O-Wax", "Flexiplast", "Magnaject", "SRS 866 blue" or similar.

Each wax must be checked thoroughly and repaired and cleaned if necessary.

"Setting" the stones in wax

A special tool, such as V ACU-SET must be used to position "set" the stones in the wax rapidly without damaging or scratching the latter

Before positioning the stones in the wax, "grooves" must be filled with liquid or pasty wax, such as "Disclosing wax" by Kerr.

When setting delicate stones such as cubic zirconia, garnets, tourmaline, etc., it is imperative to leave an extremely small space between the stones to prevent these from breaking after the metal is cast. Diamonds, rubies and sapphires are less delicate and can be placed closer together. The space between stones must only be visible with a magnifying glass and not to the naked eye (about 0.05 mm).

"Setting stones" in the wax

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Procedure

Suitable stones

Diamonds are without doubt the most suitable stones, as they are the most resistant to the pressure of metal. Rubies and sapphires do not create great problems, as long as they are of a certain purity and have been cut as regularly as possible. The most delicate stones for this procedure are cubic zirconia, garnets, tourmaline, etc.

Suitable cuts

Square or princess cut is without doubt the most widely used and suitable for invisible setting, although rectangular and hexagonal shapes may also be used.

For the choice of cut it is important that when a group of stones are placed side by side there are no empty spaces between them, in such a way that the metal is not visible below the stones.

Preparation of the stones

1. To make stones more resistant to breakage caused by pressure of the metal, acute angles must be dealt with in the various ways indicated below.

2. To be able to set stones invisibly, a small groove must be effected under the girth of the stone. This cut requires noteworthy experience and the use of a special machine such as the one below.

Stone grooving machine for diamonds and coloured stones in a wide range of shapes, such as princess, baguette, hexagon and others. Presented by Gesswein USA

These are the various systems and criteria for cutting a groove under the girth of the stone:

Cross section of a support net with stones


Preparing a suitable prototype

There are different methods for preparing the model.

1. Modelling in wax:
to create the model by hand with simple bench equipment, requires a high degree of dexterity and precision, for those who do not have the chance to use rapid prototyping (CAD/CAM).

2. Direct modelling in metal:
this methods is above all suitable for models with extremely geometrical shapes. A lathe or milling machine can be used to help. The support net for stones can be made with the aid of a milling machine or directly with plate and wire.

3. Rapidprototyping:
the various systems are described and illustrated in the book "The Santa Fe Symposium" by Mr. Bud Krahn, page 447, 1998 edition. Due to their high degree of precision, these are without doubt the most suitable systems, although unfortunately they have high lnvestment costs.

The most delicate part of the model is the support net for the stones, which must be created with specific criteria illustrated in the drawings below.

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Stone casting process with invisible setting by Dr Hubert Schuster

Dr Hubert Schuster - Jewellery TECHNOLOGY INSTITUTE HUBERTSCHUSTER Creazzo - Vicenza, Italy


Abstract

Casting with stones in general has now been known of and practised for many years, although great progress has been made and importance gained in more recent years, due to rationalisation in production and increase in quality.

The main reason for developing the stone casting process with invisible setting was the need to drastically decrease costs with the use of synthetic stones or cubic zirconia. In fact, these stones are extremely suitable as their measurements are usually regular and they are already prepared for invisible setting.


Keywords

Invisible setting, cubic zirconia, diamonds, ruby, sapphire, synthetic stones, princess cut, resistant, pressure of metal, purity, Square, rectangular, hexagonal, pentagon, acute angels, groove, girth, stone grooving machine, modelling in wax, model, prototype, rapid prototyping, Cad/Cam, modelling in metal, geometrical shapes, lathe, milling machine, support net, plate and wire, rubber mould, silicon, caoutchouc, vulcanisation, shrinkage, RTV, release cut, injection wax, plastic, flexible wax, special tool, positioning the stones, liquid or pasty wax, small space, magnifying glass, naked eye, embedding, liquid additive, coat, special investment, mixing instructions, boric acid, steam de-waxing, burnout oven, burnout cycle, burnout time, casting temperature, alloys, de-oxidising agent, centrifuge, suction/pressure, melting, palladium with gold, cool gradually, thermal shock, flask cooling time, finishing, automated systems, media, compounds.


Introduction

For many years now I have been researching new solutions and procedures to improve and rationalise the production of jewellery, especially in the lost wax casting field.

Excellent results have been obtained in the following procedures:

modelling techniques in wax, resin and alternative materials; casting of filigree or other extremely thin objects;casting of chains or objects with connecting pieces;union of different metals such as platinum, white gold, yellow gold, silver, etc., through casting (Bimetal casting) shiny surface casting;platinum casting and working techniques;casting with stones: diamonds, rubies, sapphires, garnets, synthetic stones and cubic zirconia and also emeralds cast with palladium white gold.

Owing to the need to reduce costs of invisible setting with cubic zirconia or synthetic stones, I started to look for a solution to replace hand-setting as this is too costly compared with the price of stones. However, this method is also extremely suitable for diamonds, rubies and natural sapphires.

This research project was supported by the firm Swarogem Austria, which also supplied the stones for several experiments. In the meantime, this method of setting has already been introduced by us to several firms in Italy, Turkey, Thailand, Indonesia and the USA. which are using it successfully.

These are the advantages:

Setting stones in wax (invisible) is easy to learn and very fast compared to setting by hand. Example: it would take approximately 6 hours to set a ring with 30 stones by hand, whereas setting a ring with 30 stones in wax takes approximately 20 minutes.Stones are set more securely and the risk of breakage or losing stones decreases dramatically.This system can be carried out with standard casting equipment and would need only a few special tools and pieces of equipment which are not expensive.Princess Cut diamonds, rubies, sapphires, cubic zirconia and synthetic stones can be used for this system and it is possible to cast in red, white or yellow gold and even silver.Only a minimum training session of a few days is required to transfer this technology and start the system of casting with invisible setting in wax.

Books: The Art of Bulgari: La Dolce Vita and Beyond, 1950–1990

For those who associate Bulgari with vivid colored stone cabochons or antique Roman coins mounted in gold jewelry, Chapman and Triossi’s book is an eye-opener. The Art of Bulgariserved as the catalog for the exhib Bulgari ition of the same name at the de Young Museum in San Francisco, intended to chronicle the succession of glamorous celebrities who have worn Bulgari from the dolce vita years of Italian cultural creativity through today. The authors also aim to trace the development of Bulgari’s creative aesthetic through compelling and sometimes surprising examples of its work. In both respects, they succeed.

The jewelry and luxury goods firm is so strongly associated with Rome that it may surprise readers to know that the founder, Sortirio Bulgari, opened his first shop in his native Greece. He later relocated to Naples, and finally to Rome in 1881, where the flagship store, opened in 1905, still stands at 10 Via Condotti.

Prior to World War II, the company operated as a traditional goldsmith shop, but thanks to Sortirio’s forward-thinking sons Costantino and Giorgio, Bulgari began to take a more contemporary direction. Jewelry inspired by Greco-Roman classicism, the Italian Renaissance, and the 19th-century Roman school of goldsmiths took hold, as Bulgari acquired important gemstones and created exclusive luxury pieces, including an emerald and diamond necklace commissioned by American socialite Brooke Astor.

In the post-war 1950s and ’60s, American movies were often filmed in Italy, where production costs were advantageous. As a result, many Hollywood stars fell in love with Bulgari’s bold new style, which featured large pieces set with colored gemstones. Most notable of these was Elizabeth Taylor, although Audrey Hepburn, Ingrid Bergman, Ava Gardner, and Gina Lollobrigida were also steady customers. Wealthy and influential socialites, including Barbara Hutton and Diana Vreeland, also became collectors.

Beginning with the 1950s, Chapman and Triossi show us the evolution, decade by decade, of Bulgari’s distinctive style. The use of color in so many Bulgari pieces stands out, but some gold and diamond jewels featured in this book, such as the Fireworks necklace and the Parentese parure, both from the Heritage Collection, are likewise dazzling.

The book devotes a chapter to pieces from Elizabeth Taylor’s Bulgari collection. Taylor is quoted as saying, “Undeniably, one of the biggest advantages of working on Cleopatra in Rome was [the Bulgari store].” It is clear how dearly she loved this jewelry, wearing her Heritage Collection platinum necklace with emeralds and diamonds to receive an Academy Award in 1966 and again when she was introduced to Queen Elizabeth II of England.

The Art of Bulgari also showcases whimsical pieces  that are relatively unknown. Such items include a gold measuring stick (1970), a silver-and-gold St. Moritz cigarette case (1977), a silver-and-gold tennis ball canister (1980), and a wonderful boat paperweight (1974) fashioned of sterling and gilded silver to look like a boat of folded paper. An exotic gold table clock with onyx, mother-of-pearl, and diamond (1980) is set off by two antique Chinese jade belt hooks.

The text is enhanced by excellent photography, with many jewels displayed in full-page plates. Original sketches of jewelry designs also add visual interest and insight, and photos of famous clientele wearing their Bulgari jewels abound. From magnificent bib necklaces and snake bracelet watches, to the whimsical Star-Spangled Banner series and ice cream cone brooches, this is a stunning look at Bulgari.

Chapman is a curator at the Fine Arts Museums of San Francisco, and Triossi, a jewelry historian and consultant, is curator of the Bulgari Heritage Collection. Together, the authors do an admirable job of presenting Bulgari’s history and cultural impact.

ABOUT THE REVIEWER

Elyse Zorn Karlin is a journalist, jewelry historian, and freelance curator. She is co-director of the Association for the Study of Jewelry & Related Arts, editor-in-chief of Adornment magazine, and the author of several jewelry books and exhibition catalogs.
http://www.gia.edu/gia-news-research-karlin-art-bulgari

How GIA Grades Diamonds

How GIA Grades Diamonds

People from all over the world send their diamonds to the GIA laboratory for grading and analysis. Our clients put their business in our hands and their trust in our expertise – and we are extremely careful with both.

ANONYMITY

Objectivity and independence are the hallmarks of all GIA reports and services, and GIA has elaborate processes in place to ensure a diamond’s anonymity through the grading process. Upon arrival to the laboratory, every diamond is placed in a custom designed, transparent storage case, and all references to its owner are removed or concealed. It is assigned a bar-coded label with a unique internal identification number that is used to track it throughout the process. Furthermore, client information is masked within the software diamond graders use to enter their assessments. We ask that our clients assist us in this process by submitting items in parcel papers free of information that identifies them as the client or refers to grading information.

WEIGHTS AND MEASURES

Diamonds are weighed with an electronic micro-balance that captures their weight to the fifth decimal place. An optical measuring device determines their proportions, measurements, and facet angles.

GRADING COLOR

Since light source and background can have a significant impact on the appearance of color, the diamond's color is graded in a standardized viewing environment. Color graders submit their independent opinions into the system. During this phase, graders are not privy to color opinions entered previously. The color grade is determined when there are sufficient agreeing opinions.

GRADING CLARITY AND FINISH

Clarity is graded with 10x magnification under standard viewing conditions. The preliminary grader carefully examines the diamond to locate clarity/finish characteristics and evidence of any diamond treatments, such as fracture filling or laser drilling.
 
Initially, a grader assigns an opinion of the diamond’s clarity, polish and symmetry, then plots the clarity characteristics on a diagram most representative of the diamond’s shape and faceting style, which is selected from a database of hundreds of digitally stored diagrams. During this step, the grader verifies all previously captured weight and measurement data and assigns written descriptions of the diamond’s culet and girdle thickness. For a round brilliant cut diamond, this measurement data, along with polish and symmetry assessments, is used to determine its GIA Cut Grade. Additional steps, including examinations by additional graders, are also taken during this grading process, and all others, to locate and identify clarity/finish characteristics and to check and double check for indicators of known diamond treatments and synthetics.
 
Depending on the diamond’s weight, quality, and the agreement of grading opinions, additional quality assurance process steps are also performed. More experienced staff gemologists may review all of the previous grading information and render independent clarity/polish/symmetry opinions. Grading results are finalized once there are sufficient agreeing opinions.

GRADING CUT

GIA provides a cut quality grade only for standard round brilliant diamonds that fall in the GIA D-to-Z color range.
 
After the color and clarity grading process, the diamond’s proportions (measurements and facet angles), along with polish and symmetry descriptions, are used to determine its GIA Cut Grade. A diamond’s brightness, fire, scintillation (sparkle and pattern), weight ratio, and durability, as well as polish and symmetry, are all considered within this final assessment of cut quality.

INSPECTION, CARE AND HANDLING PROCEDURES

At every step of the grading process, special inspection, care, and handling procedures are in place to protect a diamond’s identity and ensure the diamond is managed with the utmost care.

INVENTORY CONTROL AND ROUTING

GIA’s Inventory Control Department serves as the hub for laboratory operations. Between grading process steps, a diamond is distributed from and returned to this department, ensuring that the distribution of diamonds to graders is completely random. This is just one of several critical measures in an independent and impartial grading process.
 
Every diamond is tracked electronically so that the laboratory can pinpoint its exact location at any time, and review each step during the grading process. With thousands of diamonds, and hundreds of diamond graders, the routing and tracking of the GIA laboratory’s inventory requires a highly trained and alert staff, combined with the best support technology can offer.
http://www.gia.edu/gem-lab-how-gia-grades-diamond