The painting technique was studied on the altar bar of the Assumption Cathedral forming a single ensemble with the Cathedral's iconostasis. Artists under the direction of Dionisius are believed to have painted the altar bar immediately after construction of the Cathedral was completed in the late 15th century. Spectral and X-ray diffraction (XRD) analyses of paint pigments were carried out. Paint components included axurite, ochre, glauconite and cinnabar. The paint composition on the faces and hands of the personages and the technique of face painting were identified. The composition of the sankir (the preparative layer) below the paint used on the faces was analyzed. The study included an examination of certain variations in the colour and composition of sankirs of images from different areas of the altar bar. -- CAL