Watercolor course: the production of oil painting foundation

A painting with transparent vegetable oil mixed with pigments creates artistic images on materials such as cloth, paper and wooden boards. So how to lay the foundation of oil painting? Come and have a look!

Oil painting relies on a variety of materials, including soft and hard substrates. The hard substrate is wood, slate, metal plate, cardboard, fiberboard, etc. The soft substrate is mainly canvas. The painting of stretching canvas on a picture frame appeared in15th century. At that time, painters in Venice, the Italian water city, used marine canvases for the first time. In16th century, Venetian painting school reached its peak, and canvas was widely used. Later, how to make a foundation on canvas became a problem that painters studied at that time.

There are many ways to make oil painting base. Some people mistakenly mix a lot of ingredients together, and even insist that the more ingredients in the ingredients, the better. What's more, some people around us simply don't paint white on the base, but paint white on the canvas, which is really ridiculous. Most painters hardly pay attention to the importance of foundation and mistakenly think that it is not important to paint on what foundation. However, foundation not only has a great influence on the brightness of the surface of the work, but also has a great influence on the future service life of the work and the interaction between colors after compatibility.

Many painters think that oil paints can cover each other at will, so foundation is irrelevant. If the background color is light grayish white, then the color of the picture gives people a clear feeling. If heavy colors such as deep red are added to the background color, the picture color will appear dirty and greasy. After a while, the color coating below will come back. In addition, a good painting base can make the initial color layer closely combined with the canvas, which is convenient for the long-term preservation of the work and prevents the picture from cracking, falling off and oil absorption. It can be seen that painting is particularly important on the basis of what kind of painting. Below I introduce several common methods of making painting foundation.

The first layer of gum base: the production of the first layer of gum base is very important, not only the combination with canvas mentioned above, but also the elasticity after the production of the first layer of gum base. The first layer of rubber base must be done well and cannot be penetrated by oil. If it is oil-permeable, the oil will corrode the picture for a long time. The glue used in the first foundation includes rabbit skin glue, bone glue, fish fat glue, gelatin, casein glue, egg white glue, egg yolk glue, methyl cellulose, 107 glue, latex and so on. Many of them think that rabbit skin glue is the best choice and stick to it. The melting point of rabbit skin glue is 46℃ ~ 47℃, which can be said to be a high melting point in animal glue, which can avoid the high viscosity of pictures at room temperature, that is, pictures are not easy to absorb dust at room temperature.

Here, taking rubber skin as an example, this paper introduces the production of the first rubber primer: first, break the rabbit skin rubber, then soak it in water for 6 hours, and put about 7% ~ 10% rubber in the water (of course, it depends on the hot and cold weather, if the weather is high, add more water at this time). If necessary, soak the rubber with a little water first, and then add water. The water temperature of glue is between 25℃ and 30℃. When the temperature drops to 17℃, you can scrape glue on the canvas.

Put the inner frame nailed to the canvas with the picture facing up, pour the rabbit skin glue on the middle side of the canvas, scrape the glue horizontally with a special scraper, and then scrape it up, down, left and right until the whole canvas is glued. Pay attention to the temperature of the glue during scraping, and move quickly. Finally, scrape off the glue that seeps into the back of the canvas. []

Put the glued canvas in a ventilated place, and after drying, gently polish off the protruding sections on the canvas with pumice or sandpaper. When there is a convex hull on the canvas, you can put the canvas upside down on the smooth slate and gently knock it flat with a small hammer. We know that the glue at the bottom of the canvas has two functions: on the one hand, it covers the small fluff on the canvas, on the other hand, it blocks the pores of the canvas to prevent the pigment from penetrating into the bottom of the painting. Scraping glue is the most difficult step in the process of painting foundation, and it is very important to control the temperature of glue solution. If the temperature of the glue is high, the glue will penetrate into the back of the canvas, and the glue

The temperature is low and uneven, and it is not well combined with canvas. We usually use white latex for scraping glue. White latex is sensitive to heat and alcohol, so we should use rabbit skin glue. When the glue base is completely dry, if you scratch the back of the canvas with your nails, the canvas will crack, which means that if you use too much glue, the picture will easily crack in the future. This is an unqualified rubber base. After the rubber base is finished, scrape an oily base or rubber base on it as needed.

Oily base: The standard oily base is one part of white powder, lead white or zinc white and two parts of cooked linseed oil. The method is to mix and grind, and scrape it twice on the rubber base with a knife. But don't add too much oil when grinding the bottom material. Too much oil will cause more technical problems in the picture, which is not conducive to painting. Oil-based is characterized by delicate picture and good toughness, and it is not easy to crack when it is accidentally slightly collided. Less affected by environmental climate change, the disadvantage of oil-based is that it is easy to make the color layer fall off. However, when painting, if the operation is improper, it is easy to make the picture absorb oil, and because linseed oil is used at the bottom, it will make the picture "yellow".

Gum base: also known as oil-absorbing base, 70% gum is added to water to calculate one part, and then one part of white powder and one part of zinc white are added to mix. The foundation should be dried naturally, not exposed to the sun or the sun, which may cause cracks at the bottom. After drawing the foundation, we will find that the canvas is slack, because the canvas area will be stretched after drawing the foundation, so we have to tighten the wedge again to tighten the picture. When it is wet in summer, the picture will absorb moisture, so the canvas will "sag". When it is dry in winter, the picture will be too tight. Therefore, seasonal factors should be considered to adjust the wedge tightness. Filter the bottom material to remove impurities before use. After the first primer dries thoroughly, before the second primer is made, it should be polished gently with fine sandpaper.

. After the first foundation dries, apply the second foundation. If you want to get a smooth surface effect, you must scrape it obliquely with a knife. Remember to scrape with a knife at the beginning, don't brush first and then scrape, because that will leave gaps at the beginning and cracks will occur later. Foundation thickness should be moderate, too thin is not acceptable, too thick is easy to cause shedding. Some painters will add a small amount of alum to the primer in order to solidify it, but this will make the glue yellow and brittle. Spraying formalin solution on it to cure the substrate can reduce the above disadvantages.