Carrageenan is that the carrageenan is first dissolved and filtered to remove cell wall debris. The carrageenan is then precipitated from the clear solution either by isopropanol or by potassium chloride. A hybrid technology in which seaweed is treated heterogeneously as in the semirefined process exists, but alcohol or high salt levels are used to inhibit dissolution. This process is often used on South American seaweeds and gives some of the cost benefits of semirefined processing, while allowing a wider range of seaweeds to be processed, however, the naturally low cellulose levels in some South American seaweeds allow them to be
Tyrian purple this ability has sometimes also been historically exploited by local inhabitants in the areas where these snails occur (Some other predatory gastropods, such as some wentletraps in the family Epitoniidae, seem to also produce a similar substance, although this has not been studied or exploited commercially). The dog whelk" Nucella lapillus", from the North Atlantic, can also be used to produce red-purple and violet dyes. The Phoenicians also made an indigo dye, sometimes referred to as "royal blue" or "hyacinth purple", which was made from a closely related species of marine snail. The Phoenicians established an ancillary production facility on