What is marble name art

Real and fake types of marble

Marbling and shades

While you can find light to pure white marble types in Carrara, Italy, in Tuscany, there are mainly colored types in France and Belgium. This is because the deposits in Carrara are geologically older. The limestone was exposed to tremendous pressure and extremely high temperatures at greater depths and is therefore harder and lighter.

Crystalline marble in its purest form is white like the Carrara marble of the "Statuario" variety, which Michelangelo used for his sculptures around 1500. The warm tone of the polished, white sculpture marble is based on the fact that the light can penetrate to a certain depth and is reflected there on the differently oriented calcite crystals.

It is also easier to work with than the color-veined one. With veins there is a great risk that the stone will crack and break. The colored marbles are also of particular aesthetic appeal.

Impurities, i.e. foreign components, are responsible for the color and pattern. They discolor the limestone and give it a patchy or vein-shaped appearance, sometimes streaky or cloudy.

For example, iron compounds color yellow, red and brown. Graphite colors gray and black. Petrified shells and snails also illustrate the structure of the stone. These geologically younger limestones are also marbled green, purple or very colorful in some places. The floors, pillars, chimneys, tables and clock cases of the French castles of the 18th century were made with preference from colored marble.

Real marble or stucco marble?

Real or fake? One wonders sometimes when looking at marble columns and walls in baroque castles and churches. Small cracks or flakes then reveal the origin. The supposed marble is a stucco marble. To produce this mass, the finest alabaster plaster is mixed with water and glue.

It has to be alabaster plaster because it becomes so hard that it can be polished to a high gloss. The glue prevents the plaster of paris from setting too quickly and hardening. This means that the viscous mass can be processed for a long time.

Next, paint comes into half of the plaster of paris and is kneaded well as in a dough. Then the mass is halved and mixed with part of the uncolored half. This dough is now lighter. It is also divided again and one half is kneaded with the white plaster of paris.

The process is continued until a sufficiently good color gradation has been obtained. The stepped parts are now layered on top of each other. If you cut this plaster dumpling open, you can see a color gradation from dark to light.

Then you prepare a so-called wet veining by mixing different colors and finally a so-called dry veining, which consists of colored powder. The colored gypsum dumpling is wrapped in it, cut into cubes, put back together to form a dumpling, which is finally cut into finger-thick slices.

These are glued to a surface on the wall with gypsum glue and have to dry out there first. In the end, this one-centimeter-thick layer is processed in seven grinding processes until it is only two to three millimeters thick and shines like marble.

Marble from the laboratory

At the "Geological Institute" in Bayreuth, a simple limestone from the Eifel has been artificially made crystalline marble. Under the microscope it can be seen that this simple limestone is geologically fine-grained, but structured in a disorderly manner.

The small limestone sample is pulverized in a mortar and then especially carefully coated. It is important that only the pulverized limestone may be changed in the following process and not the surrounding area. A ceramic jacket is placed around the sample envelope. It can withstand particularly high temperatures and there is also a cube-shaped hard metal shell that can withstand extreme pressure conditions.

The conditions that normally take place in the earth's interior to produce marble can now be simulated: a press simulates a depth of 3000 meters with a weight of 400 tons on the tiny sample. A temperature of 500 degrees Celsius is now generated via a power connection.

These values ​​for pressure and temperature are reached after about five hours. It now takes another twelve hours for the limestone sample to become a geologically genuine, coarse-grained marble.