LIMOGES AND THE HISTORY OF BERNARDAUD PORCELAIN

The Chinese began making hard-paste porcelain with kaolin during the Tang Dynasty (8th-9th centuries AD). When Marco Polo traveled in China in the 13th century, he noticed a delicate, transparent type of ceramic unknown in the West. He called it porcellana after a white shell by the same name. This gave rise to the word “porcelain,” designating an art form that would soon be all the rage in Europe.

Everyone was fascinated by the secret ingredient in porcelain: kaolin was the crucial element to this new form of alchemy.  It was this ingredient that imbued porcelain with its translucency, flawless white luster and sonority.

In the 18th century when porcelain production began in France, the reputation of Limoges porcelain spread quickly.  Soon the mere mention of the name of the city would instantly bring to mind the art of porcelain making. One reason of the principal reasons for the notoriety of Limoges porcelain was kaolin. This white clay, essential to the production of hard-paste porcelain, was discovered in the Limousin region in 1768. 

Limousin not only possessed an abundance of this rare substance, considered to be the “white gold” of the region but also lush forests, that provided an abundance of wood to fire the kilns, and  fresh water streams to power mills that ground raw materials. 

In Limoges there existed a pool of skilled labor, essential to a craft industry like ceramics, which had been producing Limousin enamel since the Middle Ages.  These skilled craftspeople had already established a reputation for exceptional work.

The story of Limoges porcelain began in 1771 and ever since, it remained in step with history as well as trends in techniques and styles.Today numerous artists and designers continue to create beautiful, functional objects that perpetuate the art and reputation of Limoges porcelain.

PRIMARY MATERIALS OF THE CASTING:

The three minerals

Porcelain paste is made of 50% kaolin, 25% quartz and 25% feldspar. These substances are diluted in water, then ground, mixed, sifted and filtered. They are presented in slab form before being converted, depending on manufacturing techniques, into pastes of varying liquidity.

Pastes

Slip: liquid paste used for casting.

Semi-hard paste: deaerated and kneaded into the shape of a cylinder of semi-hard paste, used for calibrating.

Powder: treated by spray drying to get a powder granulate which is directly compressed by isostatic pressing.

Molds

The first phase in the manufacturing of a porcelain piece is the creation of a model. From an image (which represents the finished object in its final scale), the modeler must create the object in plaster to a “raw size” scale, which is 14% bigger than the actual size of the finished piece. This is done in anticipation of the shrinkage which occurs during the firing phase. The model (which is the only reference object) is the basis for the master mold, also known as the core. This is then the basis for production molds which enable the mass production of porcelain pieces. These are made of plaster, resin or polyurethane coated steel.

Casting is a process used for hollow pieces (coffee pots, vases, soup tureens, etc). Slip is poured into plaster molds. The porosity of the plaster absorbs the water contained in the paste and fixes it against the sides of the mold. After a precise period allocated for setting, proportional to the size of the piece (about thirty minutes for a soup tureen) the excess slip is rejected. The pieces are then taken out.

FROM CALIBRATING TO GLAZING

Calibrating is a process used in the manufacture of round and raised pieces (cups, salad bowls, etc). A semi-hard paste slab is introduced into a mold which is itself placed on a whirler. A metal template descends and flattens the paste, spreading it against the sides of the mold and cutting away any excess paste. There are two types of calibrating – jollying, when the template provides the interior profile of the piece, and jiggering for the external profile.

Isostatic pressing is a process that has been used since the eighties for the manufacture of round and flat pieces like plates. The paste in granulated form (powder obtained by the spraying of slip) is compressed at a pressure of about 350 bars inside a steel and polyurethane mold. The porcelain powder compacts and forms the object. Drying time is eliminated.

After the pieces are taken out, the drying process begins. The time will vary between twelve to twenty four hours depending on the size of the objects. During the drying process, the pieces shrink by 3%.

Handle sticking entails the addition of fittings such as spouts and handles using slip strengthened with an added binder, as well as piercing the holes in the spouts of tea and coffee pots.

Fettling enables the removal of seams caused by the division of the mold into several parts and any other imperfections. 

Pieces undergo a first firing at 980°C in kilns which are currently fuelled by natural gas. This firing known as bisque hardens and dehydrates each piece, making it porous so that the glaze fixes itself to the surface.

Glazing 

After the first firing, the pieces are brittle and porous. This porosity enables the process of glazing. For a smooth and shiny appearance each piece is hand dipped into a glaze slop. Unglazed objects have a matt appearance and are known as biscuit. Glaze is made of the same ingredients as porcelain paste, but the proportions are different. Glazing is a very elaborate manual technique which ensures an even thickness on the surface of each piece. For such precise work it is fast: a glazer can do 1,200 saucers per hour.

SECOND FIRING TO SELECTION

Pieces then undergo a second firing known as “grand feu”, at 2,552°F for 24 hours in gas-fired kilns. The purpose of this firing is to vitrify the paste and the glaze to augment the whiteness, translucency, resonance and hardness of the porcelain. It is during this firing that the piece undergoes significant shrinkage (10 to 12%) in relation to the model and reaches its final size.

Selection is the last stage in the manufacture of white products. Each piece from production is individually checked and graded according to quality.  Despite many prior quality checks, over 25% of the production is rejected during the selection process. The most common defects are stains, cracks, patches of missed glaze, deformations or splits. Some defects can be repaired. After the first firing, the pieces are brittle and porous. This porosity enables the process of glazing. For a smooth and shiny appearance each piece is hand dipped into glaze slop. Unglazed objects have a matt appearance and are known as biscuit. Glaze is made of the same ingredients as porcelain paste, but the proportions are different. Glazing is a very elaborate manual technique which ensures an even thickness on the surface of each piece. The rapidity and precision of this work is impressive: a glazer can do 1,200 saucers per hour.

FROM INSPECTION TO QUALITY APPROVAL

Decoration
The complexity of decoration varies according to the style of the collection. Certain unique pieces are hand-painted and craftsman show incredible dexterity using a wide variety of paintbrushes.
In the majority of cases, decals or leaf decorations (which use the same technique as transfers) are affixed by hand on the white porcelain. They are dipped in water to detach the motif from its paper support and are then placed on the piece. These decals are made using different printing procedures, originally lithography, but currently serigraphy. Bernardaud is one of the very few manufactures to have its own printing plant.

Lines and fittings (handles, spouts, etc) are all hand-painted. These decorative techniques are the most common. In the case of special orders, it may be necessary to use more specific techniques such as incrustation or gold relief.

Incrustation is a porcelain decoration process which uses acid engraving. The decal printed with protective varnish rather than color is applied to a piece. This varnish, which is an acid resist material, is applied by brush to the rest of the piece with the exception of the motif which is to be engraved. It is then dipped into a bath of hydrofluoric acid which “attacks” the glaze, thus engraving the cavities of the design. The piece is then rinsed in petrol, detergent and water before being decorated with two consecutive layers of gold (brilliant then matt) or bright platinum, necessitating two firings.

Gold relief is a decorative technique of embossed gold motifs applied by brush with a special paste. After firing, the decoration is dusted with fine gold before another firing.

Gold polishing
For pieces containing gold, the final operation involves gold polishing. When fired, gold has a matt appearance. Once polished – rubbed with a cloth and sand – the piece takes on a shiny new appearance.

Quality control
Before shipment to a final destination, every piece is carefully checked after every operation to ensure that Bernardaud outlets around the world provide products of only the highest quality.

Source: Bernardaud