TNT was first prepared in 1863 by German chemist Julius Wilbrand and originally used as a yellow dye. Its potential as an explosive was not recognized for three decades, mainly because it was too difficult to detonate and because it was less powerful than alternatives. Its explosive properties were first discovered by another German chemist, Carl Häussermann, in 1891. TNT can be safely poured when liquid into shell cases, and is so insensitive that it was exempted from the UK's Explosives Act 1875 and was not considered an explosive for the purposes of manufacture and storage.