To minimize the degree of discoloration, it is necessary to strictly control the process.
① Bottom layer: as thin as possible, with proper glue content, which will neither absorb oil nor leak oil, nor slip.
② Color layer: Strictly follow the principle of fat cover and thin cover, and use toner with caution. If the bottom pigment contains too much oil, it will cause the upper pigment to slide or peel off after drying. The more oil, the more serious the discoloration.
Dry the color below and cover it with the color above. If the color of the lower layer is not completely dried and directly covered, it will absorb oil, become dull and dirty, and the surface has no luster. This situation is irreversible, so it must not happen. Whether the color layer of oil painting is dry or not can not be judged by eyes or hands. Dry surface does not mean that it can be covered. Generally, it is safer to wait for a week or so for a medium-thick color layer to be covered.
③ Pigment: The less the oil content, the better the quality of pigment, the weaker the discoloration and the unqualified domestic pigment. All domestic pigments can't meet the standard of painting a storable oil painting. Not only does the oil content exceed the standard, but they also contain various additives that cannot be disclosed, which makes the pigments with incorrect colors more ugly during the drying process, and the drying speed is too slow, so it is difficult to draw an oil painting with normal speed without oil absorption. The general quality that imported brands can buy in China will not be too good, but it is slightly better than domestic ones. What Windsor Newton can buy in large quantities in China is the so-called joint venture goods, which are of poor quality and cannot be used. There is also a Windsor Newton original student-grade, the quality is slightly better, and there will be no Chinese on the original packaging. In addition, it is relatively small and expensive.
(4) Toner: Do not use the three-in-one oil containing Dammam resin easily. Although this kind of thing has been used as a fool's toner by domestic students in recent years, most of it is abused. Dammam can increase the luster of the color layer and partially cover up the luster loss caused by oil absorption, but the color changes unchanged. Dammam itself will not change, but the linseed oil in the three-in-one oil will change and the wrong drawing speed will be developed. If the bottom pigment is not dried, it will be covered by a new color layer, which will lead to the darkening of the bottom pigment.
When learning oil painting, especially at the beginning stage, it is best to use only linseed oil and turpentine. Only by mastering these two basic materials can we truly master the material attributes of oil painting. Many top players only use these two things. A painter is not a chemical experimenter. It is not that the more formulas, the better the painting, and the indiscriminate use of blending agents will be counterproductive. Dama must be used with caution. This kind of thing is neither oil nor diluent. For oil painting, it is another kind. Sometimes it appears in oil paintings to help painters increase the viscosity of color layers. Most of the time, it is used as a special interlayer binder, not for color layer. When used in color layer, it will increase the fluidity of pigment and make the color tasteless and gaudy. If you don't want your painting to look tacky and earthy, you must use this kind of thing with caution.
Linseed oil is the direct cause of pigment discoloration. Good pigments have low oil content, and dry and good painters save oil when painting. If you use oil such as gouache, the oil painting will be seriously discolored. So it is counterproductive to develop the habit of painting oil with gouache training. The longer gouache painting takes, the worse the habit, the more difficult it is to draw oil painting, the method of oil painting and the strength of pen.
Linseed oil in the background color can be mixed with turpentine. With the increase of color layer, the composition of turpentine will decrease steadily, but the fat cover is thin. In addition, it is best to use sun-dried heavy oil for linseed oil. Fresh flaxseed oil is too fluid, and it dries slowly, changes color seriously, and is very thick after drying. The discoloration is the weakest after drying. Of course, if you don't have this oil, you'd better make it yourself. It's no trouble, but it takes time. Pour the crude oil into the dish for half a year before use. Open it and dry it. The so-called gutter oil sold in the market can't be bought. It's all deceptive and toxic.