The Gouda Glasses
The church is famous for its stained glass windows: 'The Gouda Glass. They include images from the Bible and history.
Part of it was manufactured between 1555 and 1572, before the church was in Protestant hands.
The glasses St. John's contain 50% of all the sixteenth-century glass in the Netherlands.
In the ambulatory glasses 9-19 tell about the life of John the Baptist. (See "Overview glass")
After a break of more than twenty years, the Protestant governors (1594-1603) completed the glass in a dozen years.
The glass with Christ and the twelve apostles (45-57) high in the choir deserves our special attention.
At the outbreak of the Second World War (1940-1945), all glasses had already been removed from the church and safely stored elsewhere.
The Liberation Glass (28a) from 1947 keeps the memory of this period alive.

The Regular Glasses
Under glass 14 there is access to a small chapel, which was built in 1934 for seven small stained glasses (58-64) taken from the church of the Convent Regular. In this monastery, founded in 1419 in " the country of Steijn" near Haastrecht, Erasmus received his priestly training. For safety reasons the Regulars settled in Gouda in 1551.
After the demolition of their church in 1580, the glasses received a place in the choir of St. John (in the glasses 20 and 21). They date from 1556 -1559 and were made in the workshop of Dirck Crabeth.
After 350 years they were removed in 1934 and restored in to a place in the newly built Van der Form Chapel. Thus, a modest but precious possession was added to the already vast cultural wealth of St. Jan’s. The chapel was named after the man from Rotterdam responsible for the restoration of the glasses as well as its funding; Willem van der Vorm. Of this fascinating story a booklet available is available in the shop.

The glaziers
To the design and realisation of the glasses many famous glaziers have contributed. The best known among them are Wouter and his brother Dirck Crabeth.
Of almost all glasses the original full-size drawings (cartons) have been preserved, the art-historical value is unprecedented.
On the basis of these cartoons the glasses could be repaired for centuries. The last major restoration took place from 1900 till 1936.
From 1984 to 1989 a special conservation session took place, during which all glasses were provided with protective glass from the outside.