Decorative Panel with Birds, stained glass panel, 1629. Museum no. 465-1905. The central medallion shows the Infant Christ between Mary and Joseph, with God the Father and the dove of the Holy Spirit above. At the top is a coat of arms and below an inscription recording that the panel was given to Heinrich Venradius of Zwolle by his friend Joannes Nicolaus Venradius of Münster in Westphalia.

This panel illustrates very well the art of 'painting on glass'. Instead of forming part of the design, lead lines are used only to join the panes of glass together into one panel. The artist then painted the images with enamel paints and yellow (silver) stain, rather like painting on a canvas.

From about the middle of the 16th century new techniques for producing decorated glass had been introduced. Glass paints known as 'enamels' were used to paint directly onto the glass. To produce the colours, metallic oxides were added to a ground glass (frit) mixture. The resulting colour range included delicate yellows, greens and reds, as we see here.

The technique was to grind coloured glass to dust and mix it with 'fat oil' or gum and water - this is called the 'medium'. In the furnace the medium would be fired away, and the particles of coloured glass would melt and adhere, more or less firmly, to the sheet of glass.

A much wider range of colours could be obtained from enamel paints but since the colour is applied to the surface it lacks the richness and transparency of glass that has been coloured in the mix (pot-metal).

The 'frame' of the panel is painted with images of birds and plants copied from the zoological and botanical treatises that were popular at the time. The central image depicts the theme of the Two Trinities: Joseph, Mary and the Christ Child, and God the Father, God the Son and the Holy Spirit.