Clayey stones are the basic materials for the development of terra cotta squares, made up with more than 50 % of silico-aluminous minerals (clay). The remaining part is composed of a diversity of non-clayey materials (sand, limestone, oxides, silicates, iron materials), whose presence or not depends on the sedimentation of stones. After extraction of raw materials, they are shaped, dried and then cooked in specific kilns whose temperature range is from 900°C to 1150°C.

The variability of clayey materials (depending on their origin) explains the diversity of terra cotta squares obtained, such as the final colour. Generally speaking, calcareous clay (rich in lime, > 7%) and ferruginous clay (rich in iron, > 5%) are distinguished.

When cooking, calcareous clay change colour varying from pink to yellow, all the lighter since cook temperature is high (disappearance of iron oxides and hydroxides, and appearance of ferro-calcareous compounds). Ferruginous clay cook red, except for cooking at very high temperature. Other genuine colours (old-looking, grey, brown, yellow...) can be obtained with the addition of “engobe” or additives (manganese bioxide, limestone, lime).

Finally, porosity of terra cotta squares can be higher than 10% : it is higher for calcareous terra cotta.

               NATURAL STONES

Natural stones for building materials are extracted as big blocks, from open-air quarries or underground galleries. Then, blocks are cut, following the desired uses and forms. Finally, a finish stage can be added: polishing, laying, firing...

France owns a large pallet of materials, with nearly 400 varieties, 250 of them are calcareous stones and granites. Sandstones, slates and marbles add to them. Within the framework of our activities, a more detailed description of marble is done hereafter.


They are metamorphic and calcareous stones, having sedimentary origins. The nobility of this material has always been linked to its rarety, its heaviness (density) and its toughness (tender), favourable to its polishing. They exist in a multitude of colours and can have blotches, as a result of the presence of metallic oxides. An authentic characteristic of marble concerns its remarkable thermic effusivity : Indeed, whatever the surrounding thermic conditions, marble is “cold” to the touch, which is appreciable in places where weather conditions are warm.

Because of their chemical composition, marbles are not resistant to acid or very basic products (lemon, coca, bleach), leading to the formation of marks.

Marble maintenance is divided in three stages which are sanding, cristallisation and polishing.
Sanding permits to clear marks and scratches and to level joints. Cristallisation takes place thanks to a superficial chemical reaction of marble, allowing to give it back its natural brightness. Finally, polishing allows to bring brightness and colours out, highlighted by cristallisation stage.

N.B : Depending on the persons and professional circles, several terms deal with marbles. Hereafter is a table to avoid any confusion :

For marble specialists and professionals, the term  « marble » stands for every stone which can be polished ! Then, marble can be sometimes used to designate eruption stones such as granite, porphyre, jaspe and albatre.



This treatments, said « natural », are not used by NET AZUR TRAITEMENT for  the numerous drawbacks they own.  Linseed oil, hard oils, warm or cold-emulsion wax are mainly concerned.

The use of linseed oil and hard oils is based on the saturation in fat of terra cotta,  and so prevents it from marking. Nonetheless, laying of oil on terra cotta having variations of porosity and density can bring about an irregular penetration, which will cause variations of colours looking like marks. Besides the fact the treatment changes the floor colour, a frequent renew is necessary and is long to dry (“sticky” sensation under shoes, even after one year of the intervention). Moreover, the treatment is not ecological and is harmful for the health (presence and evaporation of solvents during drying period), contrary to generally accepted ideas!!!


On request of customers, products used by NET AZUR TRAITEMENT for inside treatments are solutions of aqueous, acrylic polymers and polyethylenic waxes. The role of acrylic polymers is to increase the adhesion of the protecting layer on the support, and also its UV resistance; the one of polyethylenic waxes is to increase the the layer resistance to impacts. This treatments show lots of advantages, contrary to treatments using natural waxes: They do not modify floors colour, a range from mat to bright is possible, once laid on the treatment does not need to be renewed (resistance and lifetime from 5 to 15 years). Finally, because the solution is water-based, drying time, is shorter and more ecological (organic solvents free) than a product having organics.



Chemically speaking, saltpetre stands for potassium nitrate KNO3. In building field, saltpetre is the result of water loss and cristallisation of this salt leading to a whitish pulverulent powder, forming on old wet walls.

The presence of saltpetre and other mineral salts on new buildings is one of the secondary effects of humidity risings, thanks to capillarity within the materials. This whitish deposits are frequent in areas where water is polluted by nitrates or naturally rich in nitrates.

In cellars or old wet houses, saltpetre is one of the products of development of bacteria which feed on ammonia coming from underground waters and of potassium carbonate present within walls and terra cotta. Process completes in contact with dioxygen (present in the air) to form potassium nitrate or saltpetre. Whitish deposits can be often seen in old buildings close to or surrounding an old septic tank, ammonia forming from urine.

Saltpetre and minerals are present in the whole thickness of old wet walls and grounds, and concentrated on the surface of materials. For the most courageous ones:


ATTENTION : The presence of saltpetre on your grounds means a problem of humidity or infiltration, and so a problem of watertightness !!!



Wooden floor is a floor decking, made with assembling floorboards.

Massive parquet is machined in one and only wood board. Depending on its thickness, it is either nailed-laid on joists (for thickness above 20 mm), or “plain-glued”. In case of underfloor-heating, glued-laid is compulsory. Massive parquet is proposed either as “rough-planed”, or pre-sanded, or treated in factory (varnished or oiled); Moreover special finishing such as aging or “rough sawing” exist.

Laminated parquet is a wooden floor composed of 2 or 3 layers of wood bringing each one its qualities. The surface layer is made of noble wood which gives its appearance. Its manufacturing process allows to diversify in numerous essences, colours, appearances...
Generally speaking, it is manufactured for an economic, fast and floating laying. The “wearing away” layer is, at least, 2,5 mm thick. A 3,2 mm thickness is a standard (renewable three times maximum).

Floating parquet is a wooden floor where floorboards are glued together or assembled with a “clic”-manufacturing.

Parquets for bathrooms must have two properties : naturally rotproof wood (teak, wenge, iroko, mutenye, doussie or acacia), with an oiled finishing protecting the wood from humidity. Sealing between floorboards is compulsory. Likewise, oiled parquets including sealing exist for laying in bathrooms. 

Wood essences used for parquets are as wide as their density (hard, medium or soft), or their colour (light, blond, ginger, red, golden, dark, genuine...). Hereafter are some wood essences we can find on market :

ATTENTION : « Laminate » is not a type of parquet : indeed, the surface layer laminate decking is not wood based but is made up with a picture of wood printed on a composite layer protected by a resin. So, its renovation can not be done by sanding, but by the complete renewal of its whole surface.