Painting on raw plaster with paints (we make a fresco)
Wall painting with paints on raw plaster is called a fresco ... This word comes from the Italian word which translates as "fresh". At the moment, this is far from the most popular idea for interior decoration, where painting on dry walls is often used.
The dry method of painting makes it possible to work without rigid frames in time, undemanding to the base, and most importantly - it can be done by a person who does not have the qualifications of an artist using templates. But with frescoes, this approach will not work.
Art in the form of painting on raw plaster appeared in the ancient Mediterranean. This method has become popular due to cheap paints that are made from local mineral-type raw materials and are diluted with water. In Rome, fresco-type painting adorned the homes of wealthy people, as well as public buildings, and an example of such works can be seen in Herculaneum and Pompeii, where the painting was perfectly preserved thanks to Vesuvius, who stands nearby - the cities were covered with ash at the very beginning of our era.
The fresco developed in the Middle Ages, where it could become an indispensable attribute temples. Especially famous were the Italian masters, whose fresco was a sign of the master's aerobatics. Services for fresco painting were in well-deserved demand - such painting was almost eternal, because the paint soaked into the surface of the plaster and set along with it. When dry, it began to fade a little, but this was compensated for by the main purpose of the fresco - it was carried out in large interiors, where the impression of the painting was obtained at a certain distance from it. Painting on a wet plaster layer prevailed in churches until the 18th century, and was gradually replaced by other types of interior decoration.
Lime-type plaster, consisting of slaked lime and sand, will be applied to the surface of the walls in several layers, the top of which will be covered with painting. Mural paints are water-soluble, and they are made on a casein, lime or even silicate base. When applied to the surface of raw plaster, they begin to absorb into it and, as the mortar sets, they remain in it, staining calcium carbonate. From the point of view of chemistry, such a process will look like the following method:
Ca (OH) 2 + CO 2 = CaCO 3 + H 2 O
In this case, Ca (OH) 2 is slaked lime (i.e.
calcium hydroxide), and CO 2 - carbon dioxide. The picture obtained in this way will be an integral part of the walls, and it will not work to wash it off. You can only paint over or knock down the plaster to the fullest.
A fresco can become one of the types of monumental painting.Unlike an easel, when you can shoot a picture and transfer it to another place, but with a wall painting this will not work.
Initially, all monumental art was designed to be not an independent work, but part of a common complex. It may be that this is roughly said in relation to the artist's works, but the fresco in the apartment will become an alternative to wallpaper or painting, but only with a higher price.
Before deciding on such a decoration for your wall surfaces (or ceiling, if the height allows), you should think about the composition that you will place here. It is better to try to consult a specialist on this matter. The thing is that the picture you like may not fit into your interior at all.
What looks great under the dome of cathedrals is not at all suitable for decorating walls in Khrushchev houses. Another point in painting on wet plaster that is important to warn about is qualifications. Most often, modern master artists do not have the skills of plastering, and the masters themselves often have a bad deal with artistic talents. The masters of the Middle Ages owned both the first and the second, and so it was easier for them.
You have two options for creating the situation:
There is one more very important warning - if you do not have special knowledge about the properties of paints and varnishes, light shadows, composition, and artistic skills in general, you should not start learning from a fresco. Believe me, this is not the case at all. You will be driven into the narrow frames of the plaster layers, and are more likely to spoil both the wall surfaces and the material. You should assess your capabilities realistically.
Painting on plaster using water paints made from two stages - plastering, and also painting. In this case, both processes will be superimposed on each other. For this reason, each step should be considered in detail. The fresco is made according to the most popular plaster coating in Soviet times - lime-sand mortar. This solution will be diluted in proportions of 2 to 8, where 2 is slaked lime, and 8 is sand.
The finishing layers are diluted in a ratio of 2 to 5, and instead of sand, it is worth using a powder made from brick powder.
There is lime on sale, which is in the form of a lime dough, as well as quicklime powder and fluff powder (slaked). Cheap lime is made from industrial waste and is lean - the content of calcium oxide in it is much less, and it is extinguished extremely slowly, and sometimes it can take a year to extinguish.
The use of low quality lime under the fresco is not recommended.Due to slow extinguishing and a large amount of impurities, it will produce efflorescence, due to which it can lag behind the wall surfaces and form ugly streaks on the surfaces of the plaster layer, or even begins to delaminate.
Previously, artists tried to thoroughly grind and mix lime to achieve perfect maturity. At the moment, there is an opportunity to purchase clean lime and start extinguishing it at home, and if there is no place for this, buy fluff. The sand for the solution must be clean, without impurities. The best option would be river sand. It is better to sift sand through a fine strainer - unlike masonry solutions, plasterers adore fine-grained sand, and the solutions on it will be more plastic.
If you feel sorry for the time, then it is worth doing sifting at least on the upper layers.
The plastering process is carried out in three stages:
At least three layers are in question. The maximum number can reach seven, and is extremely important for lime mortars.
When applying a layer of more than 1 cm, such plaster tends to crack, and therefore, the curvature of your walls should be assessed in advance, and additional plans may be required.
The best base for lime-type mortars is a brick-type wall, and concrete is slightly worse. If your wall surfaces are pasted over with wallpaper, then they should be removed, as well as the layer of the old plaster type, and especially if it will not adhere well. Curved walls should be reinforced. For this purpose, a plaster mesh may be ideal, and at the same time it is better to use products made of polymer material under the fresco.
Previously, craftsmen mixed straw into the lower layers, and flax fibers into the upper layers. They are not necessary at this time, but reinforcing a very thick layer will be extremely important.
For the wet plaster painting technique, temporary beacons should be attached to the wall, which will serve to level the first layer. Spraying can be done using a trowel or from a pump (in industrial volumes, they use it specifically). Surplus should be removed by means of a rule.
If the spray is thick, it makes sense to stretch it twice or even three times, and this way you can avoid cracks. In this case, it is better to put the mesh in this layer, pulling out the beacons in advance. When the spray begins to partially set, and you can proceed to the primer. This requires a thicker mortar, which will be applied to the surface of the walls with a trowel and rubbed with a trowel. Remove the excess using the rule.
In this case, the quality of the work performed by the rule or level should be monitored - it is at this stage that the geometric alignment of the walls is completed.
The solution for the covering-type layer is made more liquid, and fine sand or even grated bricks are used as a filler.The latter option is preferable because it perfectly retains moisture, which is so important for the full setting of the solution. The layer itself is small, no more than 0.2-0.
5 cm, and apply it with a float.
Note that in one step for fresco painting, apply as much cover layer as you are able to cover with a fresco. For this reason, labor productivity is best determined in advance. An experienced master will paint from 6 to 9 square meters per day, but this will depend on the selected composition. Attention to detail dramatically reduces productivity.
Since the lime solution is alkaline , when mixing paints, pigments that are resistant to alkali are needed. These include the following ocher, cinnabar, chromium oxide, ultramarine, mummy, soot, manganese peroxide, red lead, lemon, umber, sienna, burgundy, orange and scarlet. At the moment, there are much more such pigments, but when buying, you should always take into account a couple of factors - solubility in water and resistance to alkaline agents. Lack of attention to alkalis can result in both color change and perfect discoloration. If you are in doubt about how the pigment will behave in the future, you can recommend testing it.
To do this, it is important to dilute it in the composition you want to work with (water and lime, casein and lime, water), and apply it to a previously prepared plaster piece. If you are a beginner, you should do this with all pigments. It is important to thin the paint lightly and use a soft brush when applying.
If you will be painting walls for the first time, it makes sense to prepare a template on a paper surface in natural size. It is applied to the walls and the contours of the main figures are pierced with needles to get an imprint on the plaster layer.
After that, you can begin to trace the contours, and it is better to start working with light transitions, and then gradually go to black. Layering is a great option to give the finish color a better finish. Light areas can be whitened with diluted slaked lime, and only after that you can start applying the basic colors. At the end of the working day, the plaster unfilled with painting must be cut obliquely with a clerical knife to the thickness of the covering-type layer so that the layer is invisible in the future.
In addition to the usual casein and aqueous solutions, there are methods for diluting paints and varnishes on liquid glass and eggs.
Paints that are obtained by mixing pigment and eggs are called tempera paints. They are great for calcareous substrates because the egg white albumin will react with the lime to produce a very strong substance called calcium albuminate. Such compositions are diluted with beer, kvass or even wine, adding the ingredients of eggs and pigments to them.The yolk as a base has one, but a very significant drawback - the dried paint, which is diluted on the yolk, begins to lose its brightness. The situation can be saved by covering, but at the same time such a painting will cease to be a fresco, and squirrels work much better in this respect.
tempera painting is much denser and better retains tone.
For painting on wet plaster outside, paints based on liquid glass are perfect. They are bred on a palette, and as a covering layer for them, a solution of 2 to 8 is ideal, in which 2 measures of lime and 8 measures of ash. This porous rock perfectly absorbs paints and varnishes, and when in contact with lime, liquid glass will give a more stable, and still insoluble substance, much stronger than a fresco. If you have weighed all the pros and cons, and decided on a fresco in the house, then you should approach the process differently from the easel composition.
Good frescoes will create a mood at a distance, and it is difficult to paint small details on them, and it is not necessary. It would be much better to pay attention to colors, contours, light shadows, because it will depend on them whether the fresco will fit into the interior of the home or not.
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