The stonework of the Rose Window was completed in the mid 13th century but the stained glass was added near the end of the 15th century to commemorate the end of the War of the Roses and honor the Tudor dynasty.
After fire destroyed the South Transept roof in 1984, inspection revealed that the stained glass in the Rose Window was severely cracked. The 73 panels, containing 7,000 pieces of stained glass had crazed into about 40,000 pieces! Miraculously it was all still in place.
Craftsmen secured the stained glass with adhesive film before removing it, one section at a time. Special adhesives - which would mimic the refractive properties of the glass - had to be researched and were specially developed by 3M corporation before the window could be restored. Each restored section is sandwiched between layers of clear glass - the restorers jokingly refer to it as a Tudor sandwich - and the whole is further protected by more sheets of glass.
The stained glass restoration process, along with the restoration of the roof, took about four years and cost $4 million. Essential Visitor Information for York Minster