Dyes included woad for blue and less frequently madder and lichens for reds and purples. Alizarin was discovered before purpurin, by heating the ground madder with acid and potash. This alizarin concentrate comprises only 1% of the madder root. In Viking age levels of York, remains of both woad and madder have been excavated. The madder dyestuff is combined with a dye mordant. He developed a red dye made from the roots of the madder plant. Other goods exported included wheat, durra, honey, gold, ostrich feathers, senna, madder, and civetone. They used bright shades of madder red. Still another group of pigments comes from living organisms, such as madder root. There was a trade in yellow madder (Stil de grain yellow) and mohair. On that tour Tristania was supported by Rotting Christ, Vintersorg, and Madder Mortem. Historically it was derived from the roots of plants of the madder genus. Chapman realised that it needed to be "madder", and came up with the parrot idea. Rose returns to her world with instructions from Rose Madder to "remember the tree". Pierre-Jean Robiquet and Colin began producing garancine, the concentrated version of natural madder.