Of course, the mediaeval painter could mix his colours with the water of the wet plaster which was put upon the walls of the churches. This method of painting upon "fresh plaster" (which was generally called "fresco" or "fresh" painting) was very popular for many centuries. To-day, it is as rare as the art of painting miniatures in manuscripts and among the hundreds of artists of our modern cities there is perhaps one who can handle this medium successfully. But during the Middle Ages there was no other way and the artists were "fresco" workers for lack of something better. The method however had certain great disadvantages. Very often the plaster came off the walls after only a few years, or dampness spoiled the pictures, just as dampness will spoil the pattern of our wall paper. People tried every imaginable expedient to get away from this plaster background. They tried to mix their colours with wine and vinegar and with honey and with the sticky white of egg, but none of these methods were satisfactory. For more than a thousand years these experiments continued. In painting pictures upon the parchment leaves of manuscripts the mediaeval artists were very successful. But when it came to covering large spaces of wood or stone with paint which would stick, they did not succeed very well.