The wooden board is not convenient to take pictures, it is necessary to apply substrate. Traditional gesso substrate is made of chalk (or especially prepared gypsum) and glue (gelatin). Skin glue is glue of animal origin and the best is made of rabbit bones, recently used substrate is based on acrylic. The substrate is applied by brush in several layers, or less by blade. After drying, substrate is flat and glace with abrasive paper.The substrate may be acrylic or based on glue and chalk.
Acrylic substrate is a modern, universal foundation for all painting techniques. It is quality and made of chalk powder and sinthetic acrylic binder with additions. It can be purchased in stores with painting equipment.
Substrate called Gesso (Italian), or Levkas (λευκός-Greek) is based on skin glue and chalk. It is even known in the Middle Age, and recipe for its preparing is not changed until today.
Gesso was used in all medieval icons. Although it is more difficult to prepare and application compared to the acrilyc substrate, he is still in use today because of tradition and authenticity of the icons.Artist who want to imitate a large medieval artists in everything, does not limit itself to the canons and techniques of painting, but wants to use the same materials and fully believing that neither the selection of materials for making icons not accidental but that carries a certain symbolism.
Method of preparing Gesso
Chalk powder is the main ingredient of the acrylic substrate and gesso.The difference between these two substrates is in the binder. Acrylic is a synthetic binder. Skin glue is the antique wood glue made from animal bones and less animal skin.Method of preparing Gesso is as follows: First of all, to melt glue in the water. Melting in the volume ratio of 1:10. Most practical way to determine the right scale is next: Pour water into glass jars. Measure the height of the water from the bottom of the jar and mark it on the jar (for example 10 cm). Share the measurements with 10 (10:10 = 1 cm). Highlight the line that will be the calculated value more than the first line and mark it on the jar.Add gradually thinner in the granules until the water level with the first line does not take up another line. In this way you added exactly 1/10 glue to the amount of water.
Glue is melting for several hours. It must be heated to be completely melted. It is best to warm up with duble dishes: jar with glue put in a pot with water. Pot with the water is heated and thus indirectly heat glue in the jar. This precaution is necessary because glue is must not be to much warm (over 60 degrees Celsius), because properties of the glue can be permanently changed, its stickness can be reduced. When the glue melted away in the water, gradually add required quantity of chalk powder. Eleven teaspoon of chalk powder add to 0,2 liters of water. When chalk is added into a glue, it is necessary to mix and with constant mixture warming keep the temperature little lower than 60 degrees. To chalk could fully absorb the glue it is necessary to pass a few hours.
Thus prepared gesso is ready for application.Gesso is always applying hot. If it is cold, it is necessary to re-warm. It is very important that Gesso is warm!! Because if not, air can not emerge from the some of applied layers of the substrate. In dried coating will remain the bubble, which will later, in leveling and glazing, appear as a hole. Gesso is applying by brush width of about 5 cm. It is important applying thin layers. If the layers are thick, there will be bubbles of air trapped in the substrate layer, the same happens when cold substrate is applied to icon.Each layer is applied only when the previous layer has dried, which in practice means that it can be applied 1-3 layers per day, and so until the applied layers count 15-30. It is better to be more layers, because after the grading substrate will be rather and equable.
We should not be impatient and applied thick layers, so it would not happen that, as in the case of the cold substrate, remain trapped air bubbles.It is also important that air humidity should be higher than normal. At home the best place for working is bathroom, but it can works in other rooms too, because into the house is always increased humidity in relation to external humidity regardless of the season. You should avoid rooms that are heated by electric heaters because that heaters dry the air. You should not work outside!! Because the outside is dry air regardless of whether you work in the sun or in shade. It can occur fast drying and cracking the substrate. When all the layers are applied, substrate requires longer drying, at least two days. When it is well dried, you can start leveling and glazing.
When you are working with acrylic substrate everything is much easier, and rarely have the anomalies during drying. It is necessary to dilute the substrate and apply on the board thin layers, the following apply when the previous layer has dried. The substrate is applying without heating and it is less prone to incidents of irregularities, if the air is dry or if the layers are thicker.
Acrylic substrate is more quality than gesso after drying, because thanks to the elasticity of acrylic, it is less prone to cracking from gesso. I think that in addition to high-quality acrylic substrate is not necessary to use traditional gesso, especially because applying acrylic surface is simpler than applying gesso. Using antique substrate is justified if artist wants with using gesso to preserve the authenticity and tradition of medieval iconography.Leveling and glazing substrate. Leveling is a procedure which removes irregularities arising from the brush trace which applied substrate or from gauze below the substrate, while the glazing is removal unevenness that was created by leveling and using rough abrasive paper. It can be said that the leveling is rougher grinding and glazing is finer grinding, in order to obtain a fully flat substrate with few irregularities.Irregularity is any bump: unevenness, scratch or hole that seems to substrate is not completely flat.
Leveling and glazing substrate
Process of leveling and glazing is the same at Gesso and the acrylic substrate. Leveling is done with abrasive paper fineness of 100-400. At first it is done with rougher abrasive paper and subsequently with the finer. Leveling can be done manually or can be used lapping machine.It is necessary to grinding very long, spend more abrasive paper until all irregularities occurred during the applying substrate is not removed and until only remain the irregularities that were committed by rough abrasive paper. These irregularities can be eliminated with finer abrasive paper of 600-1000, which is called glazing. Glazing should be done as long as there are any irregularities.
The verification of the correctness substrate should be done in bright sunlight or, in the absence of sunlight, in strong lighting.It is necessary to face the board with substrate to a strong source of light, so shadows reveal irregularities in the background. There is one trick, which facilitates the identification of irregularities: a little pigment powder, any color except white, spil into the icon and spread and rub all over with wider brush.During glazing gesso substrate, colored like this, pigment will keep in holes and it will be completely removed only where is glazed well.
polish- hand sanding gesso
When you run out of the pigment from substrate this will mean that is well glazed. If, despite all your efforts irregularities remain, you should make a mixture of white pigment and acrylic, the density of mud and applay with hands - rub into the substrate. After drying it is necessary to glaze again with fine abrasive paper and remove the odds, so that the applied mixture remain only in the holes and scratches. If you have done everything as well, on the substrate should not be any irregularities. The substrate is finally ready for further preparation, before application of gold and colored layers.Do not neglect this part (preparation of the substrate and the board)! It is very important! Although at first sight does not seem so, in further work and practice you will realize that the beauty and the ultimate effect of icon greatly depend on the quality made background!