The violet is permanent, and by boiling with soap, passes into rose color. The madder-red colors are less susceptible of alteration by acids the more they have been brightened by soap and the ...

The bright red dye discovered in the cave was made from the roots of a plant called Rubiaceae over 15,000 years ago. In some areas, the plant is known as woodruff or madder. It grows throughout ...

The dyes had diverse sources, ranging geographically from India to Mexico. So the composition of red lakes may disclose ... equally be made from the root of the madder plant or cochineal extracted ...