Glue-size (in German Tiichlein or Tüchlein, sometimes referred to as Distemper in contrast to tempera) refers to a technique in painting where pigment is bound to cloth (usually linen) with glue extracted from animal skin. Typically the unvarnished linen was in turn fixed to its frame using the same glue. Glue was a popular binding medium in the 1400s, particularly among artists of the Early Netherlandish period, who used it as an inexpensive alternative to oil. Although a large number of works using this medium were produced, few survive today, mainly because of the high perishability of linen cloth and the solubility of the hide glue. Well-known and relatively well-preserved—though substantially damaged—examples include Quentin Matsys' c. 1415-25 The Virgin and Child with Saints Barbara and Catherine[1] and Dirk Bouts' c 1440-55 Entombment.[2]
A binding agent for pigment was made by boiling animal skin mixed with other organic tissue and applied to linen, itself prepared with a thin layer of glue.[3] Generally the linen was ground, or treated, by both the glue and also white chalk, which allowed a surface suitable for underdrawing and a base that would not absorb the final layer's pigment.[4]
The advantage of using glue as a binder is that the colours render as matt and opaque, as opposed to the translucent appearance associated with oil, textures suited to austere or mournful images. Many reds and blues bound in glue would have appeared with a brilliance and intensity difficult to achieve with oil. Unfortunately, the surviving examples have greatly deteriorated over time, having suffered from colour alteration due to exposure to light. Furthermore, the solubility of glue derived from animal products has meant that the accumulated layers of dirt cannot be removed without damaging the linen or dissolving the pigment.[3]
Although it allowed fine linear detail, subtle tonal transition and at times vivid colourisation, by the end of the 1400s the medium, along with egg tempera, had fallen out of favour. Oil painting had become predominant among the artists of the early Northern Renaissance, mainly due to the innovations in oil by Jan van Eyck[5] and Rogier van der Weyden.[3]