Carrageenan each plant weighs approximately 1 kg. The "E. cottonii" variety has been reclassified as "Kappaphycus cottonii" by Maxwell Doty (1988), thereby introducing the genus "Kappaphycus", on the basis of the phycocolloids produced (namely kappa carrageenan). After harvest, the seaweed is dried, baled, and sent to the carrageenan manufacturer. There the seaweed is ground, sifted to remove impurities such as sand, and washed thoroughly. After treatment with hot alkali solution (e.g., 5–8% potassium hydroxide), the cellulose is removed from the carrageenan by centrifugation and filtration. The resulting carrageenan solution is then concentrated by evaporation. It is dried and ground to specification.
Purple is a spectral color. On the CIE xy chromaticity diagram, violet is on the curved edge in the lower left, while purples are on the straight line connecting the extreme colors red and violet; this line is known as the line of purples, or the purple line. During the Middle Ages, artists usually made purple by combining red and blue pigments; most often blue azurite or lapis-lazuili with red ochre, cinnabar, or minium. They also combined lake colors made by mixing dye with powder; using woad or indigo dye for the blue, and dye made from cochineal for the red.