The Copenhagen Målarlaug Window Project on Amaliegade 3 in Copenhagen conducted byt the Copenhagen Painters Guild was a unique test. In 2001, its windows were painted with 10 different paint systems ranging from plastic paint to linseed oil paint. The test was intended to investigate which type of paint fared best on windows over 10 years of exposure. Among other criteria, it was judged on cracking, peeling, mould, etc. In 2011, the final results revealed that linseed oil paint consistently fared best out of all the paint types tested.