History and technology of painting on wet plaster

An ageless art form that has been practiced for thousands of years is painting on wet plaster. Many civilizations have employed this method, often known as fresco, to produce magnificent wall paintings that endure. Vibrant colors and intricate designs combine to tell stories and capture the essence of various eras in frescoes found everywhere from the Sistine Chapel ceiling to the ancient ruins of Pompeii.

Painting on wet plaster is an exacting and skill-based process. Painters have to work fast to apply pigment directly onto the surface before the plaster dries. The pigments are absorbed by the plaster as it cures, incorporating the colors into the wall itself. Because of this special technique, frescoes maintain their beauty and resilience over time despite aging and weathering.

To perfect this art, a variety of methods and materials have been developed over centuries. Through the development of fresco painting technology, artists are now able to achieve amazing effects, moving from basic earth pigments to more complex mixtures. Despite these difficulties, fresco painting is still regarded as a noble art form, valued for its capacity to turn plain walls into works of art.

Topic	Description
Origin	Painting on wet plaster, known as fresco, dates back to ancient civilizations like Egypt and Rome.
Technique	Artists apply pigments directly onto fresh, wet plaster, allowing the colors to bond with the surface as it dries.
Materials	Natural pigments mixed with water are used, and the plaster is often lime-based.
Durability	Frescoes are long-lasting due to the chemical reaction between the plaster and pigments, making them resistant to fading.
Famous Examples	The Sistine Chapel ceiling painted by Michelangelo is one of the most famous frescoes in history.

A little history

Painting walls using paints on wet plaster is referred to as "fresh" or "fresco" in Italian. The evolution of fresco has a history spanning over a century. The invention of coloring agents on lime by the ancient Romans marked the beginning of "fresh" painting.

Instead, the paintings discovered in Pompeii were created on dried, moistened plaster (secco), which was then covered with materials containing tempera or wax. The compositions used in the paintings included a small quantity of lime. There are surviving frescoes that adorned Romanesque churches built in the eleventh and twelfth centuries. Painting on dry plaster was once again popular in the fourteenth century, following a protracted period of neglect.

Complete wall painting on wet plaster, or buon fresco, which is the application of paint based on lime to recently laid plaster, did not emerge until the 16th century, during the Renaissance.

According to Michelangelo, frescoes are brave forms of art because they demand a bold, precise hand, the capacity to apply a stroke without needing to be corrected, physical difficulty, and the ability to work quickly and for extended periods of time. As a result, not every artist could work in fresco, and a fresco test was used to gauge skill.

The rightful creators of the fresco technique are the Italian masters. Italian painters were the ones invited to paint palaces, cathedrals, temples, and other imposing structures abroad.

The process needed a minimum of five layers to be applied, specific lime, solution, and paint preparation, close adherence to every technological detail, and a significant amount of time. The maximum area that an artist could decorate in a 16-hour day was 1.6 m². Every day, a layer of freshly laid plaster had to be removed from areas that were left unpainted and reapplied the following day. They spent years studying the method.

The demand for fresco masters quickly declined with the introduction of wallpaper, the widespread use of glue paints, shifting tastes, and the desire to expedite the finishing process. Today, the true art of painting on wet plaster using water-based paints is mastered only by a select few master restorers and custom finishing artists.

Masters use modified technologies all the time, which saves them money and enables them to use some modern materials and techniques. There are ways to mimic the look of fresco.

Ancient civilizations such as Egypt, Greece, and Rome have a long history of painting on wet plaster, a technique called fresco. Using this technique, pigments are directly applied to newly laid plaster, allowing the colors to set into the surface as the plaster dries. Fresco painting developed over centuries, and Renaissance masters like Michelangelo used it to produce magnificent pieces such as the Sistine Chapel. While new tools are available today thanks to modern technology, the fundamentals of fresco painting are still based in tradition and combine art and craftsmanship in a timeless manner.

Techniques of wall painting and painting with water-based paints on wet plaster

Thus, the evolution of one wall painting technique has been traced through three stages:

• on a dry wall (tempora) with paints containing lime;
• water-based paints with the addition of lime after the plaster has dried and then re-treated (secco or alsecco), or on a fresco underpainting with tempera;
• lime paints on damp, freshly laid plaster (fresco, as fresco, buon fresco).

Modern artists employ a variety of wall painting techniques, each with its own variations.

Painting on a new composition involves a series of sequential operations, most of which are carried out in the order listed below:

• preparation of the wall;
• preparation of several solutions;
• sequential application of each solution;
• preparation of paints;
• creation of a sketch, application to the top layer of plaster;
• hermetically sealing the wall with film;
• painting on wet plaster (direct and reverse order);
• drying.

Preparing the wall surface

Not every type of wall material can be painted using this method. For instance, there are various reasons why aerated concrete blocks or other weak materials shouldn’t be painted with frescoes.

• the blocks are weak and cannot withstand the weight of the plaster coating;
• aerated concrete has a high ability to absorb moisture from the mortar;
• if the integrity of the wall is damaged, the artist"s precious work is lost.

A true fresco could have one of three bases:

• brickwork;
• sandstone blocks;
• iron blocks (stone) are considered the best wall material for fresco painting.

Nonetheless, contemporary artisans also create frescoes on walls made of concrete.

In order to prepare a brick wall, you must:

• removing cement or unusable gypsum plaster;
• cleaning from stains;
• deepening the inter-brick joints by 2-3 cm;
• applying an insulating and adhesive coating;
• complete drying.

Fresco painting is not appropriate for cement plasters.

In the past, the base was insulated in the following ways, which were required to stop water from penetrating the wall material:

• section of wall with an area of ​​½ sq. meters were heated with a wide gasoline or kerosene flame;
• the surface heated area was quickly coated with a heated mixture of asphalt and coal tar (1:3);
• fired once with a lamp (the heated mixture was absorbed into the brick);
• “sharp” (unrounded) sand poured onto a board was transferred to a warm tar mass, to which grains of sand were glued;
• processed the next area.

As a result, the wall became more waterproof and more adhesive. But the need for such a coating only arises when water rises along the wall from below due to inadequate insulation.

Current regulations stipulate that the height difference between the wall’s surface should not be greater than one centimeter. Consequently, the protrusions are removed. To create a rough surface, metal brushes are used to treat the brick. Notches are all over smooth brick. Dust is taken out.

Large-headed galvanized hooks or nails were another antiquated technique for attaching the plaster to the base (again, it’s important to separate the metal from the plaster). These products retained a 2-4 cm layer of plaster. Fiberglass meshes are now employed.

Preparation of a special plaster mortar

Only slaked lime that has been aged for several years is used for fresco. They even purchase ten-year-old Austrian limes in certain instances. They use three-year-old material for home use. While high-quality, ready-made fluff is easier to purchase. After being aged for at least two weeks, it is combined with the dough. Chalk mixing with lime is not acceptable.

Networks usually advise using river sand that has been cleansed (washed, free of silt and clay). Sand was used back then because it was really needed, not just rounded. The standards for hygiene remained unchanged. When using "sharp" sand instead of a solution with rounded sandstones, you can achieve a stronger coating. You will require multiple fractions of sand:

• for the underlying layers – larger;
• for overlying – smaller;
• The thinnest sand is needed for the top layer.

According to research on Tyrolian fresco coatings, lime plaster with the highest strength is produced by dolomite sand.

Brick powder is a filler that effectively retains moisture in the mixture. For the top layer, it is preferable for them to replace the plaster mass’s sand. The plaster solution’s shelf life can be prolonged by adding small pieces of brick and powder, which is crucial information for painters.

• The dough for the underlying layers – 1: 4;
• mass for the upper layers – 1: 2.5.

In the past, chopped hemp was added, and hemp retains moisture well. Only the bottom layers were filled in with this material. Check out our in-depth plastering sand article.

Features of plastering

Plastering was done in two layers both during the Renaissance and afterwards:

• the lower one – with a solution with coarse sand, which (the solution) was allowed to dry;
• the upper one – with a solution with fine-grained sand/brick powder, which was renewed daily (the part of it that did not have time to apply the drawing).

Currently, the lime mixture is applied in two to three layers, starting with a brick that has been thoroughly moistened. The plaster layer is three centimeters thick overall. The final layer, which is painted, has a maximum thickness of 4 mm. To guarantee strong adhesion, the intermediate layers—aside from the penultimate one—are not leveled.

Paints for painting

Wet plaster can be painted with paints that have been diluted with water. These can be modern adhesives such as water-based or acrylic, even fluorescent, or traditional mineral dyes that are resistant to alkali and do not deteriorate when in contact with lime plaster. Master colorists rightfully revere dyes like yellow ocher, smalt, blue azure, umber, and others that help create multicolored pictures.

Lime that has been slaked for at least three years has long been used as whitewash for frescoes. For a few weeks, it is filled with water and left to remove some of the causticity. Drain the infused liquid every day and replace it with fresh. After that, it is moved to a pot with glaze, put in the oven, let it boil, and then allowed to cool. Remove extra water, get the balls ready, and let them dry. The lime can then be ground and applied like a water paint.

Paints in various shades are kept in small containers; baby food jars work well for this.

When paint is first applied to a wall, it appears vivid and rich. However, they get lighter and lose brightness when they dry. In the past, umber stone was used to estimate the color of the fresco since it absorbs water instantly. The paint takes on a shade that is similar to the fresco as it dries quickly. These days, they paint a test piece to get an idea.

Additionally, tempera paints are utilized. Egg yolk serves as the binding agent in them. Tempera is used for touch-ups and underpainting.

Preparation and application of the sketch

It is impossible to paint on wet plaster without first transferring the drawing to the wall. A small drawing is transferred using the cellular method. They developed the "cardboard" technique for large fresco "canvases." On cardboard, the sketch was created using a 1 to 1 scale. After applying cardboard to the wall, they could see how the fresco would appear.

For each section, they plastered the surface in multiple locations after "binding" the cardboard to the wall with nut-sized holes. The cardboard then cut. Holes were drilled along the lines of the drawing for the purpose of piercing with a needle or dusting with coal.

The sketch lines were moved to the area that needed painting after a piece of cardboard was affixed to the wall in accordance with the markings. These days, a stencil or thick paper can be used.

Some artists used paint to decorate cardboard. This allowed for the timely correction of errors by comparing the completed painting with the sketch. Museums hold the cardboard creations of renowned artists.

Preservation

The top rough layer of plaster is leveled, and then a thin film is applied to the entire wall surface to hermetically seal it and prevent air from leaking through. Using a roller or a sponge to smooth the film, air is gently forced out from underneath. A piece of film is cut out, exposing no more than one square meter, before painting. In this manner, the water required for the entire painting of the fresco is kept in the plaster for the required number of days.

Drawing a picture

Painting on wet plaster can be done in a variety of ways. Some of the masters begin with dark regions and work their way up to lighter ones. Similar to watercolor painting, someone starts with light strokes and works their way up to dense, dark ones. Soft brushes are used for writing so as not to disturb the wet film that has formed on the surface of the recently applied plaster coating.

The artist completes pieces at a time. only interrupts the portion of the preservative film that he can continue painting throughout the shift.

Additionally, the paint’s consistency varies, ranging from liquid to paste-like. Applying multiple layers of paint is possible, depending on the artist’s intentions. One drawback: the paint application is permanent. Instead of the paint’s water being absorbed by the coating, the calcium in the lime solution serves as a barrier to shield the brushstrokes.

Use of frescoes in modern interiors

Large rooms are painted using the method of applying water-based paints on wet plaster. A painting like this appears stunning from a distance.

A fresco works just as well for interior design in a home; the only requirement is that the painting’s plot and size, which are created using water-based paints, match the room’s dimensions. Additionally take into account that the painting will be viewed up close, which alters the viewer’s perception of it.

There is a long and illustrious history of painting on wet plaster. With the use of this technique, artists have been able to produce magnificent, enduring masterpieces directly on walls, as evidenced by the vibrant frescoes of ancient civilizations and the iconic works of the Renaissance. Its timeless appeal stems from the special fusion of craftsmanship and artistry, where each stroke becomes an integral part of the overall design.

Although this method’s technology has changed over time, its fundamental ideas haven’t changed. Although the process is now easier to accomplish with modern materials and methods, painting on wet plaster still requires patience, skill, and a thorough understanding of the medium. Today’s artists are still motivated by this age-old technique and are constantly coming up with new ways to investigate its potential.

Painting on wet plaster is still a potent medium for expression, whether one is following tradition or exploring new artistic directions. This technique is guaranteed to enthrall and inspire future generations due to its historical significance and innovative potential.

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