When we buy a picture for decorating the wall at home, most of the cases the technique it was made is secondary. Its beauty matters and if it fits for the surroundings and if the size is good. Maybe it is right. But it’s worth to know broadly the painting techniques because it may affect the value of the picture and if in doubt, it helps to define its age or origin also.
The pigment of tempera is dispersed in an oil-water emulsion. The emulsifier keeps together these two components. The simplest one is lecithin can be found in egg. Its yolk and albumen are mixed with powder pigments. The paint can be distempered before drying. This was used also by the ancient Romans, but the medieval icons were made by this technique too.
Oil paint changed tempera during the Renaissance. The pigment is dispersed in drying oil (linseed oil, nut oil, poppyseed oil). Its appearance coincides the evolvement of landscape painting which specialties are best implemented by this technique. The paint is dense, sticky, dries slow, so the colors and lines are mixable and shapeable still on the canvas. It hardens after drying and produces a shiny and resistant surface. The artists always mixed the paint freshly until the possibility for hermetic storage.
In case of aquarelle (that is watercolor painting), easily soluble pigments are mixed with water and it is applied in dilute state on the paper which is firstly wet. Fine, light, opaque colors are produced this way. This technique was used at first for sketching, later it became an individual art. It was most popular in Europe in the 18th-19th centuries, but primeval cave paintings and ancient Egyptian murals were made by water-based paints also.
Pastel is a transition between drawing and painting. Powder paint extruded to rods with minimal bonding are used for applying to the dry paper. The paper has special surface, it is grainy or on the contrary, velvety for better dispersing the powder on it. The colors are mixable longer on the paper, the picture is formable by finger, brush or even a piece of rag. Pastel appeared in France at the end of the 15th century, it was one of the favorite techniques of impressionism.
Engraving is the summary name of multiplier graphical arts. It has two groups. 1. Relief printing: the part of the picture which shouldn’t mark are dented into the surface. Printing ink is applied to the rest of the surface which is transferred to the paper. E.g.: wood-engraving lino-cut, stone engraving. 2. Gravure printing: lines of the picture are dented into the surface the paint is being applied here and it is cleaned from the topping parts. The paper is pressed into the hollows and the ink is transferred this way. E.g.: line engraving, etching, acid-washing.
In case of uncertainty in purchasing a painting, ask for help of a professional.