After tests at the Hahnemühle paper factory, the rags were used by local factories and then cleaned before being used to make the paper; the colours of the counterfeit and original notes then matched.[26] When the initial paper samples were produced, at a factory in Spechthausen, they looked identical to British notes in normal light, but looked dull in ultraviolet light when compared to the originals. Langer surmised it was because of the chemical composition of the water used for making the paper and in the ink.