FR2847577A1 - Protecting and decorating substrates having a porous surface, e.g. ceramics, comprises applying two coatings, sealing and waxing, all at room temperature - Google Patents

Abstract

Protecting and decorating a substrate having a porous surface comprises applying a first coating of inorganic material, drying, applying a second coating of (in)organic material, drying, sealing and waxing, all of these steps being performed at room temperature. Independent claims are also included for: (1) milk of lime for use in the above process, comprising air-slaked lime, oxide pigments, additives (talc, casein, linseed oil, gelatin glue, liquid soap, saponified wax, gum arabic, gum tragacanth and/or Silicatex (RTM; silicon dioxide fiber)), optionally a pigment fixative, and an aqueous phase in an amount of 40-60 L/100 kg; (2) object produced by the above process.

Description

PROCESS OF TREATMENT WITHOUT COOKING

OF POROUS MATERIALS

  The present invention belongs to the field of surface treatment of ceramics, and more

  usually porous materials.

  It relates to a new process allowing the application of decorative patterns of various shades and the waterproofing of objects whose surface is made of a porous material.

  such as ceramic, without having to cook the treated objects.

  Ceramic comprises all the products which are obtained by virtue of the properties of natural alumina clays and silicates and the like. The essential properties of clay substances are plasticity, which allows the shaping of moist clay paste, and the object's ability to preserve its shape after drying and cooking. These characteristics explain why ceramic objects are very common in

various applications.

  Porous ceramic products are obtained by firing at a temperature selected so as to allow only total dehydration of the clay, without causing the soldering of the pasta granules which would give a compact and impermeable mass. One finds there in particular terracotta (bricks, tiles, etc.), domestic pottery with tinted paste as well as domestic earthenware and sanitary stoneware. Those skilled in the art use different methods for molding pottery, manually or using machines, depending on the type, destination and size of the objects to be produced. After shaping then

  a drying step, cooking is carried out in an oven.

  The objects obtained are porous and permeable. They can be used as is, but more often because of their destination, it is preferable, on the one hand to make them waterproof, and on the other hand to make them aesthetically more attractive. This is particularly the case

  pottery, which has a decorative function associated with domestic use.

  Enameling pottery has long been used to suppress porosity. It gives the products a smooth and shiny surface. According to this technique, the pottery is coated with a glaze, a sort of varnish formed of substances which melt easily during cooking and form a vitreous surface layer. The application of the glaze can be done either when the piece is still raw, or when it is already cooked, which then involves

a new cooking.

  The decorations are obtained using substances which, during cooking, acquire a certain color. There are two methods for decorating pottery: you paint the baked and unvarnished object, then pass the glaze and subject the object to a new baking (decoration at high heat or under glaze); or else the baked and varnished material is painted and subjected to a third muffle firing, that is to say in a low oven

  temperature (decoration in muffle or glaze).

  Thus, the enameling technique, used for the treatment of pottery for waterproofing and decoration, requires at least one, and often two additional firing, inducing manufacturing times and energy costs

1 5 important.

  The method according to the invention provides a new technique which avoids these drawbacks by proposing a treatment of pottery at room temperature, which makes it possible both to waterproof it and to apply decorative patterns of various colors to it. Since no firing is necessary, this technique is easily applicable to the treatment of all kinds of porous surfaces, such as ceramics, stones, but also building materials, or even fibrous materials such as paper, cardboard, wood and canvas. The method of protecting and decorating a support with a porous surface according to the present invention is carried out by a treatment of said surface, essentially comprising the following steps - application of a first layer of mineral nature, - first drying - application of a second layer of mineral or organic nature, - second drying, - sealing-waxing,

  said steps being carried out at room temperature.

  The first layer, also called the bonding layer, must be made using a

  substance of a mineral nature so as to preserve the porous nature of the treated surface.

  Indeed, to have good cohesion with a second layer and obtain a patina, it

  it is necessary not to freeze the shard by closing the pores.

  Advantageously, the bonding layer consists of a limewash, comprising a) - a binder based on lime, and optionally also a filler chosen from colored or non-colored sands, natural pigments, artificial pigments , a mixture of these;

b) - an aqueous diluent.

  In the present application, the term “whitewash” is understood to mean an aqueous preparation of type 10 suspension, based on lime and which may also contain other ingredients, intended to be spread widely over a surface to be treated to form a bonding layer. such as

defined above.

  The mineral binder used in the composition of said whitewash is preferably slaked air lime or natural hydraulic lime. Indeed, among the available binders, lime constitutes an ideal mineral binder: during the drying of a whitewash whitewash, the calcium hydroxide is carbonated by carbon dioxide from the air and forms a hard, calcareous layer. resistant. From an aesthetic point of view, lime is characterized by its

  matt, very velvety, and its exceptional luminosity.

  You can use either natural hydraulic lime or slaked aerial lime depending on whether you want the setting to be fast or slow. Hydraulic lime sets as soon as it is mixed with water. It must therefore be applied immediately after preparation. Air lime only sets when in contact with air, even when mixed with water, it keeps for a very long time in an airtight container, but its drying is slower. It is found in the form of a paste or powder. In the present application, the contents of the binder are given

  for a slaked aerial lime paste with a moisture content of 36% by weight.

  The mineral binder can be combined with a filler, making it possible to increase the volume prepared and to introduce additional constituents having determined functions. In particular, whitewash may contain colored or non-colored sand, as well as pigments

  natural, or artificial pigments, or a mixture thereof.

  In general, materials giving a particular relief to the treated surface can be introduced into the whitewash, to be trapped in the thickness of the bonding layer during drying. For example particles of crushed brick, glass, plastic, paper, having rounded, pointed or flattened shapes can give a more or less rough appearance, and more or less regular. In particular, when it is desired to obtain a finish with a granular appearance, the filler may consist entirely or in part of sand, colored or not. Advantageously, such sand is provided at a rate of 5 to 20 kg

per 100 kg of binder.

  No material giving a relief effect will be added to the binder when it is desired to obtain a smooth patina effect on the treated surface at the end of the process.

  Since the bonding layer is intended to serve as the basis for a second layer having a more marked decorative function, it is often preferable that this

  bonding layer provides a neutral background, for example ivory or yellow in color.

  However, it is obvious that all types of pigments available can be used to color whitewash, the choice of shades being the aesthetic choices of the designer. Such pigments are also used for the preparation of the second layer (in the case of a

  mineral coating) and will be described in detail below.

  The pigments used in the process according to the invention described here are in the dry state in the form of a more or less fine colored powder, although other presentations, for example pigments incorporated in a support in the form of a paste, may also be used without inconvenience. Can be used mineral pigments and

  organic pigments, whether of natural or synthetic origin.

  The pigments introduced into the first layer can in particular be chosen from natural oxides and artificial oxides. In a whitewash according to the invention, the natural oxides will preferably be provided at a rate of 15 to 25 kg per 100 kg of binder. The artificial oxides will be brought in at a rate of 5 to 15 kg per 100 kg of binder. Those skilled in the art will be able to determine the quantity to be brought within these ranges of values, according to the intensity of the tones he wishes to obtain. It should be borne in mind that the color lightens by almost 50% as it dries. For the good resistance of the whitewash on the support to

  treat, it is recommended not to exceed the maximum values.

  The combination of sand and pigment mixed in the whitewash provides a grainy finish and coloring. The quantities of each component to be introduced into the whitewash are again chosen by those skilled in the art in proportion to the aesthetic effect which he wishes to obtain, but remaining within the range of the values indicated in order to preserve the

  whitewash its properties of bonding layer to the support.

  Whatever the binder and possibly the filler chosen, an aqueous diluent must be added, so as to obtain a suspension which is fairly thick, but which still spreads easily in a regular layer. For example, in whitewash intended for the application of a bonding layer, the dilution rate is around 30% to 50%, i.e. 30 to 50 liters of diluent are added per 100 kg of whitewash prepared. Preferably the dilution rate is

  between 35% and 45% based on the total weight of whitewash.

  Said aqueous diluent can of course be pure water, but can also be adjuvant water, that is to say containing one or more additives intended to supplement the properties of the whitewash or facilitating the use of the suspension , such as texturing agents, lubricants, wetting agents, polishing agents, sealing agents. For example, casein can be added to the binder to reinforce the adhesive properties of the whitewash and for its lubricating effect. This animal protein also has the advantage of having a very decorative mat finish. It will be brought in at a rate of approximately 2% of the weight of lime. Skin glue, also called "gelatin glue" or "tempera", is also used for its adhesive properties and is very suitable for decorative painting of porous surfaces. The gum arabic, the gum tragacanth allow to obtain a better hold. A synthetic product, for example Silicatex TM, can be added at the right

  from 5% to 10%, depending on the porosity of the support.

  A saponified wax or linseed oil will be advantageously added to improve the slipperiness and, if desired, to polish the treated surface after drying. Talc is used to give smoothness and slippery. It is preferably added at a rate of 5 to 10% of the weight of

lime, approx.

  A wetting agent such as a liquid soap can be included in the milk of lime, a few drops being sufficient. In the event that pigment saturation is desired for

  color reasons, a fixative may be added in the quantity indicated by the manufacturer.

  Finally, when the humidity of the support is high, the addition of a sealing agent makes it possible to reduce the drying time, or the amount of natural hydraulic lime in the whitewash. The application of the whitewash on the support can be done either by contact, with a brush, with a brush, with a sponge or other, or using a spraying means, for example with a pneumatic gun. During this operation, it is advisable to shake frequently and

  paint regularly to avoid sedimentation of the suspension.

  The composition of the whitewash is strong in bonding, so that it adheres correctly to the porous support and plays its role of bonding layer with respect to the next layer, matching the relief of the support in a uniform manner, with an almost constant thickness after drying. This thickness can vary by a factor of 50 depending on the composition of the whitewash, in particular its viscosity. For example, in the case of a whitewash composed only of lime and water, the bonding layer will generally have a thickness of approximately

  0.1 to 0.2 mm. If the whitewash contains sand, a layer thickness of up to 5 mm can be reached in order to cover the grains of sand.

  After the application of the bonding layer, a drying time is necessary for the whitewash to merge with the porous support. In the case where the binder used is lime, the melting takes place thanks to the limestone which is reconstituted by carbonation of the hydroxide.

  calcium by carbon dioxide from the air, which forms a hard and resistant layer.

  The drying time can vary from two hours to twenty-four hours depending on the water content and the thickness of the layer applied. In addition, for the same composition, the drying time varies according to the atmospheric conditions and the porosity of the support. Those skilled in the art accustomed to controlling the drying of porous parts, can appreciate whether the bonding layer is dry, for example by comparison with the feel of the difference in humidity between the treated face and the bare face of a porous piece. Proper drying of the bonding layer is essential for its good resistance to porous support and must be checked before

  the application of the second layer which will now be described.

  In the method according to the invention, a second layer, of mineral or organic nature, is applied to the porous surface to be treated previously covered with a layer

hanging and dried.

  Advantageously, when this second layer is mineral in nature, it consists of a lime milk comprising a) - a lime-based binder, and optionally also a filler chosen from colored or non-colored sands, natural pigments , artificial pigments, a mixture thereof;

b) - an aqueous diluent.

  In the present application, the term “milk of lime” is understood to mean an aqueous preparation of the suspension type based on lime and also containing other ingredients, intended to be spread over a surface to be treated to form a second layer of mineral coating such as defined above. For the reasons explained above, lime constitutes an ideal mineral binder, from the point of view of its hardness as from the aesthetic point of view. Air lime or hydraulic lime can be used as a binder for the second layer. As with the first layer, a relief effect can be obtained by introducing special materials, such as those already mentioned, into the milk of lime. For a finish with a grainy appearance, the filler can consist entirely or in part of a sand, colored or not. Advantageously, such sand is provided at a rate of 5 to 20 kg per 100 kg of binder. For reasons of ease of implementation and solidity of the coating, it will however be preferred to obtain the relief effects during the application of the first layer, and to favor the

  coloring when applying the second coat.

  It will be readily understood that it is also possible to apply a second layer formed solely of lime and water, in order to obtain a well-opaque white solid surface, at the

matt and velvety.

  We can also consider that in the case where the desired decorative effect, be it colors or appearance, is obtained by applying the first layer, applying a second layer as defined above. it's not mandatory. In a variant of the method according to the invention, it is considered that the first and second layers are combined and obtained in a single application. However, both for the aesthetic quality of the finished product and for its solidity and longevity, it is recommended to make two

  separate layers of coating before sealing.

  The coloring of the treated surfaces is obtained by applying a whitewash containing one or more pigments. Preferably, the pigments are chosen from i) earths colored with metal oxides which have a strong coloring power and are economical, such as copper, manganese, chromium, cadmium, cobalt or iron oxides; ii) crushed natural colored rocks; iii) pigments of plant or animal origin such as

  than indigo, pastel blue and purple; iv) artificial pigments.

  In general, many pigments can be used, insofar as they are miscible with water, such as for example: - whites such as chalk, whitewash, whitewash, titanium dioxide; - blacks such as ivory black, pit black, vine black, smoke black, mars black; - yellows such as Naples yellow, March yellow, cadmium yellow, yellow ochres; - oranges such as mars orange, cadmium orange; - reds such as cinnabar, cadmium red, natural red ochres, red oxides; - greens such as chromium oxide, natural silicates, sodium aluminosilicate;

  - blues such as cobalt aluminate, Prussian blue, phthalocyanine blue.

  These examples are not limitative, many other coloring substances being commercially available. It should be noted that most pigments can be presented pure or mixed with a liquid or pasty support. In the latter case the use doses are indicated by the manufacturer and the charge introduced into the whitewash consists

of the pigment + support package.

  Preferably, said pigments are chosen from natural oxides provided at a rate of 5 to 100 kg per 100 kg of binder, and artificial oxides provided at a rate of 2 to 80 kg for

kg of binder.

  Whatever the binder, the filler and the additives chosen, an aqueous diluent must be added, so as to obtain a fairly fluid suspension, which spreads easily in a thin layer. For example, in the lime milk intended for the application of the second layer, the dilution rate is generally between 50% and 60%, that is to say that 50 to 60 liters of diluent are added per 100 kg of prepared lime milk. Preferably, the dilution rate will be between 45% and 55%. This dilution rate, higher than that of whitewash, allows

  achieve precise pictorial patterns and maintain a certain transparency.

  Said aqueous diluent can of course be pure water, but can also be adjuvant water. It can contain various additives supplementing the properties of the second layer or facilitating the use of the suspension, such as texturing agents, lubricants, wetting agents, polishing agents, sealing agents. These additives are the same as those which have been described previously. The skilled person chooses one

  or more depending on the effect he wishes to obtain and incorporates them into the water of the preparation.

  Lime milk, which makes it possible to carry out the second layer of the process according to the invention, has a particular complex composition, developed specifically to meet the technical requirements already described, while offering a large choice of colors. This is why an object of the present invention is also a composition intended for the treatment of a porous support, comprising a) - air lime, b) - at least one pigment chosen from natural oxides and artificial oxides, c) - at least one additive chosen from talc, casein, linseed oil, gelatin glue, liquid soap, saponified wax, gum arabic, gum tragacanth, SilicatexTM, d) - optionally additionally a pigment fixative, and e) - an aqueous phase at a rate of 40 to 60 liters, preferably 45 to 55 liters, for

kg of said composition.

  In certain cases, the intensity of the coloration obtained by applying a lime milk containing pigments, even at the maximum amounts prescribed by the manufacturer for a given pigment, is not sufficient. The use of higher amounts of pigments is not recommended, as it leads to a relative reduction in the amount of binder and does not allow

  not to ensure good quality treatment of the porous surface.

  It is then preferable to apply to the porous surface to be treated, after drying of the bonding layer, a layer of organic nature. In general, use will be made of a synthetic resin, preferably an acrylic resin or a vinyl resin. These resins are easy to use, have good water resistance, and offer a wide variety of bright colors. The acrylic resin will be preferred insofar as it has excellent compatibility with lime because it is not sensitive to alkalis, and because it is the most decorative. Water-soluble synthetic resins are commonly used in paint and are sold as a thick liquid, which should be diluted

  until the desired fluidity for their application is obtained.

  The application of the second layer on the support can be done either by contact or using a spraying means. During the duration of this operation, the preparation to be applied should be stirred frequently and regularly to avoid sedimentation of the

suspension.

  The second layer having a decorative function, it is not systematically applied to the entire surface of the object to be treated, but only to a predetermined area. It should also be understood that the expression "second layer" is

  used here and throughout this description to designate all of the coatings

  deposited on all or part of the bonding layer. Indeed, to make polychrome decorations, different coatings (different whitewash or synthetic resin) of different colors can be prepared, and each will be applied to a predefined portion of the surface to be treated, so as to produce the chosen polychrome pattern. In this case the second

  layer will be mixed in the sense that plasters of different composition will be juxtaposed.

  It is also possible to produce a second layer, called complex layer, by superimposing several coatings of different tint on the same area, to obtain particular shades. Two conditions must be met for this. The first is to allow each coating to dry before applying the next coating. The second concerns the case where one wishes to superimpose mineral and organic coatings. It is then recommended

  first apply the mineral coating, then after drying, the organic coating.

  Thus in the method according to the invention, said second layer can be a complex layer produced by successive applications on the same area of said surface, of coatings

of different composition.

  For the application of the second coat of plaster, suitable tools will be used, for example, the sponge for smooth or almost smooth substrates, or the brush in moldings and on reliefs. Stencils can also be used, or other techniques

  still available to those skilled in the art.

  A drying time is then necessary, which will generally last on the order of one to six hours. As is, the surfaces treated with a first then a second layer according to the invention are still porous. As a result, they are not waterproof and risk being degraded and discolored during successive humidifications. They must therefore be sealed. In the method according to the invention, a sealing-waxing step is carried out at ambient temperature, by application of a water-repellent agent, then drying and application.

  a colorless wax or a dyeing wax.

  First of all, a water-repellent product is deposited on the entire surface of the treated object in order to fix the lime on the porous support and to merge the first and the second layer, which has the effect of closing the pores. The application of the water repellent, or sealer, can be carried out by spraying, immersion or the like. We can use for example an agent

  water repellent with silicone. Such water repellents are commercially available.

  After drying in the open air, a wax is applied to the entire surface of the object subjected to the treatment process according to the invention. Waxing makes it possible on the one hand to make the support impermeable to water and humidity of the air, and on the other hand to bring a matte touch and

satin patina.

  In the process according to the invention, the wax can be colorless or even dyeing. With a colorless wax, we obtain a support with a satin finish, while a dyeing wax will color the support previously tinted with the coating and give a more rustic note. The application of the wax can be done by soaking, or using an appropriate instrument such as a brush if the wax is liquid, or a sponge if it is thick. After drying at temperature

  ambient, the wax can be polished using a soft cloth.

  Many varieties of natural and synthetic wax exist on the market. Mention may be made of beeswax, floor wax, industrial ionized liquid wax commonly used for floors, and waxes used in the furniture industry. Advantageously, the wax used in the process according to the invention is chosen from a wax

  bee, an ionized industrial wax, a cabinetmaker's patina to shade.

  As has just been described in detail, the method according to the invention makes it possible both to protect and decorate porous surfaces permanently, while working at room temperature. Having no need for additional baking after biscuit-making, it is economical in time and energy, and although it was initially designed for the manufacture of decorative pottery, it quickly became apparent that the interest of such a technique extended, far beyond this activity, to the treatment of most porous surfaces. In particular, the claimed process can be implemented for the treatment of the surface of a porous support chosen from the following materials: ceramics such as terracotta, domestic pottery with tinted paste, domestic earthenware, sanitary stoneware; stone such as limestone, granite, sandstone; building materials such as concrete, cement, plaster coatings, lime coatings; fibrous materials such as

  wood, paper, cardboard, canvas.

  Finally, an object with a porous surface obtained after treatment by a process as described above is also claimed. Such an object has the following characteristics: - it is waterproofed outside, which gives it a protection comparable to that obtained by vitrification with enamel, - it remains porous inside, thus retaining the advantages of porous walls , for example by letting a growing plant breathe, - it resists humidity and temperature change, it offers great diversity in colors, it is thus very decorative, - it offers the choice of an aspect matt and satin, pastel and patinated tones, unlike the always shiny enamel. The following examples will describe in more detail certain embodiments of

the present invention.

EXAMPLE 1

  Preparation and application of a yellow bonding layer on ceramics In a 100 liter container, 1 volume of slaked aerial lime and 1 volume of burnt sienna powder are introduced. Water is added until a fairly creamy product is obtained. These ingredients are mixed using a paddle mixer mounted on a

  rotary motor, in a homogeneous mass of the desired consistency.

  The whitewash thus obtained can be transferred to the tank of an air pistol and sprayed over the entire surface of baked clay pottery, previously placed in a paint booth, until a uniform layer of desired thickness is obtained. . Then the cabin is open and ventilated until the pottery covered with a

first mineral layer.

EXAMPLE 2

  Preparation and application of an ocher grainy layer on a wall In a concrete mixer, have introduced: a) - Slaked aerial lime: 1/2 volume Natural hydraulic lime 1/2 volume b) - Ocher pigments: 1 volume Sand of grain size 0, 5 cm: 2 volumes c) - Water: sufficient quantity to obtain a product that is creamy enough to be able to spray it or float it on the wall. These ingredients are kneaded in the concrete mixer

  until completely homogenized.

  The whitewash thus obtained is applied in the following manner: wet the support to saturation to eliminate the dust and slow the setting, then apply with the float in an energetic way so that the sand takes well, a layer of at least 0.5 cm , but not higher

  1 cm to allow drying. Leave to air dry, preferably in the shade.

EXAMPLE 3

  Preparation of colored lime milks with an essentially decorative function The following ingredients are kneaded until a fairly fluid homogeneous mass is obtained: a) - Dried aerial lime: 1 volume b) Red oxide pigments: 1/2 volume - Burnt Sienna pigments : 1/2 volume c) Water: 2 to 2.5 volume - Liquid soap: a few drops The same operation is repeated several times, replacing the pigments respectively by

  cadmium orange and a red oxide.

  The lime milks thus obtained, colored in ocher, orange and red respectively, are applied one after the other to the pottery previously covered with a bonding layer prepared according to Example 1. Each colored milk is spread out using a sponge on flat surfaces, and using a small gray brush on curved or raised surfaces, without superimposing it with another milk. The pieces are left at room temperature until completely dried. They can be sealed immediately after drying, or

  stored away from moisture for further processing.

EXAMPLE 4

  Preparation and application of a second layer of organic nature with an essentially decorative vocation

  In a 4 liter container, about 2.5 liters of lazure are introduced for 2.5 liters of water.

  These ingredients are mixed using a spatula. The operation is reproduced using

  satin lazures or acrylic resins in aqueous phase, of different shades.

  Application is by brush, brush or sponge. The organic layers are applied one after the other on pottery previously covered with a bonding layer prepared according to Example 1, without waiting too long (because the setting is fast). It is possible to superimpose the shades. The color palette obtained is more vivid

than with mineral milks.

EXAMPLE 5

  Sealing of colored pottery The parts obtained after drying according to Example 3 are impregnated with a water-repellent agent of the silicone water-repellent SikaTm type by total immersion for a few seconds in an aqueous bath prepared with a volume of sealant (mouth pore) in 15 volumes of water. The proportion of sealant will be increased for the most porous substrates. The pieces are

  drained, then allowed to dry at room temperature for at least 2 hours.

  A traditional beeswax is liquefied by heating to 40 ° C, then is drawn with a brush on the surface of the pieces. After drying for 2 hours at room temperature, the decorated and waterproofed pottery is polished using a soft cloth. The pots

  obtained have a very decorative satin polychrome patina.

EXAMPLE 6

  Waxing of a stone status A stone status previously sealed according to Example 5, is coated with a tinted wax, intended to give it a lustrous and rustic appearance. A tinted wax is liquefied by heating (if necessary), then stretched with a sponge on flat surfaces, or with a brush on curved surfaces. After drying for at least two hours at room temperature, the

  status thus treated is polished using a soft cloth.

Claims (17)

  1. A method of protecting and decorating a support with a porous surface by treating said surface, essentially comprising the steps consisting in - applying a first layer of mineral nature, first drying - applying a second layer of mineral nature or organic, - second drying, - sealing-waxing,   said steps being carried out at room temperature.   2. Method according to claim 1, in which said first layer consists of a limewash, comprising: a) - a lime-based binder, and optionally also a filler chosen from colored or non-colored sands, pigments natural, artificial pigments, a mixture of these; b) - an aqueous diluent.   3. The method of claim 2, wherein said limewash comprises a pigment chosen from natural oxides, preferably provided at a rate of 15 to 25 kg per kg of binder, and artificial oxides, preferably provided at a rate of 5 at 15 kg for kg of binder.   4. The method of claim 2 or 3, wherein said whitewash comprises   sand brought in at a rate of 5 to 20 kg per 100 kg of binder.   5. Method according to one of claims 2 to 4, wherein said whitewash   contains between 30 and 50 liters, preferably between 35 and 45 liters of aqueous diluent per 100 kg of whitewash.   6. Method according to one of claims 1 to 5, wherein said second layer is   consisting of a lime milk comprising: a) - a lime-based binder, and optionally also a filler chosen from colored or non-colored sands, natural pigments, artificial pigments, a mixture of these; b) - an aqueous diluent.   7. The method of claim 6, wherein said pigments are chosen from the following: earths colored with metal oxides (oxide of Cu, Mn, Fe); colored rocks; pigments of plant or animal origin such as indigo, pastel blue, purple; artificial pigments such as chalk, whitewash, zinc white, titanium dioxide, ivory black, core black, vine black, smoke black, mars black, Naples yellow, March yellow, cadmium yellow, yellow ochres, March orange, cadmium orange, cinnabar, cadmium red, natural red ochres, red oxide; chromium oxide, natural silicates, sodium aluminosilicate,   cobalt aluminate, Prussian blue, phthalocyanine blue.   8. The method of claim 7, wherein said pigments are chosen from natural oxides provided at a rate of 5 to 100 kg per 100 kg of binder, and artificial oxides   brought at a rate of 2 to 80 kg per 100 kg of binder.   9. Method according to one of claims 6 to 9, wherein said milk of lime   contains between 40 and 60 liters, preferably between 45 and 55 liters of aqueous diluent per 100 kg of lime milk.   10. Method according to one of claims 2 to 9, wherein said aqueous diluent   includes at least one additive chosen from texturing agents, lubricants, agents   wetting agents, polishing agents, sealing agents.   11. Method according to one of claims 1 to 5, wherein said second layer is   made of a synthetic resin, preferably an acrylic resin or a vinyl resin.   12. Method according to one of the preceding claims, wherein said second   layer is a complex layer produced by successive applications on the same area of   said surface, coatings of different composition.   13. Method according to one of the preceding claims wherein said step   sealing-waxing is carried out by - application of a water-repellent agent, - drying, - application of a colorless wax or a dyeing wax 14. Method according to the preceding claim wherein said wax is chosen from   beeswax, ionized industrial wax, cabinetmaker's patina to shade.   15. Lime milk intended for the treatment of a porous support by the method according to claim 6, comprising a) - air lime, b) - at least one pigment chosen from natural oxides and artificial oxides, c) - at least one additive chosen from talc, casein, linseed oil, gelatin glue, liquid soap, saponified wax, gum arabic, gum tragacanth, SilicatexTm, d) - optionally additionally a fixing agent for pigments, and e) - an aqueous phase at a rate of 40 to 60 liters, preferably 45 to 55 liters, for kg of lime milk.   16. Application of the method according to one of claims 1 to 14 to the treatment of   surface of a porous support chosen from the following materials: ceramics such as terracotta, domestic pottery with tinted paste, domestic fae̋nces, sanitary stoneware; stone such as limestone, granite, sandstone; building materials such as concrete, cement, plaster coatings, lime coatings; the   fibrous materials such as wood, paper, cardboard, canvas.   17. Object with a porous surface, obtained after treatment by a process claims 1 to 14. according to one of