THE OTHER TECHNIQUE in use at this time was tempera. This term covers all those types of painting that employ a medium with a base of glue, either animal--egg, gelatin, cheese, blood, or vegetable--gum arabic, gum of the cherry tree and fecula. These techniques possessed the great advantage of brilliance and permanence, but they were, at the same time, subject to serious difficulties of management which in many ways limited their possibilities.

    The so-called early primitive paintings executed in these various tempera mediums possessed a charm of their own, undoubtedly due in some measure to these very limitations of technique. The impossibility of achieving realistic effects and of producing the illusion of the third dimension preserved in them the flat decorative quality for which many are much admired. This decorative effect owes much of its power to the juxtaposition of large masses of color and form, similar to the effects obtained in some of the minor arts. In this book we speak of these early paintings entirely from the point of view of plastic painting, which assumes that the aim of a picture is the representation on a flat surface of the appearance of depth. Thus, in describing the limitations of the Primitives, we refer only to technical considerations and do not imply that their works were lacking in color, in spiritual value or in emotional and decorative power.

    It is very difficult today to find in the museums any examples of the earliest tempera paintings that are in sufficiently good condition for us to follow with certainty the successive steps of the painter's workmanship. For instance, those paintings with a glue base were subject to serious damage from humidity in the atmosphere, and as soon as they were finished they had to be covered with a heavy oil varnish. This varnish unfortunately had a deep color of its own that seriously altered the harmony of the picture it covered. Then, the examples that are to be seen in the churches are often in

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