Genuine Alizarin Crimson is a fascinating ancient pigment which is also known as Madder Root, specifically made from the roots of Rubia tinctorum. The technical ways in which this pigment differ from a related pigment, NR9, usually called Rose Madder, are somewhat unclear. The Rose Madders we have encountered tend to be pink, so we infer that NR8 Natural Alizarin refers to the deeper crimson form of madder. If you happen to be an expert in historical pigments and can improve this article, please reach out.
Natural Alizarin Crimson or Madder Lake may refer to the older way of preparing Alizarin from the madder root. Synthetic Alizarin, which we call Alizarin Crimson Genuine PR83, was an innovation that led to a synthetic dye that mimics natural alizarin.
In terms of lightfastness, when talking about textiles, Alizarin is said to be lightfast, but in terms of pigments, there are different standards for archival fine art products, and we don't feel Alizarin Crimson is lightfast enough. Much conversation has surrounded Alizarin's lightfastness, and many feel it is right at the lowest end of the dividing line of what could be considered lightfast enough in artist materials.
To the extent that this preparation may be similar to NR9 it is not clear whether NR9 or PR83 is actually more lightfast. For many years it was said that synthetic Alizarin was more lightfast than the natural version, however we have also now seen reports that the opposite may be true in some cases.
In her book Natural Palettes, Sasha Duerr mentions that it takes seven years to cultivate the madder root to in order to harvest.
When used as a pigment in oil paint, this color tends to require a lot of oil, and also is associated with cracking in oil paints. The lightfastness is not very good, and the orange note in the warm crimson tends to fade out (ironically the orange note is the part associated with purpurin).
As purely a note on naming patterns that persist even among imitation hues, natural alizarin crimson tends to be a deep maroonish crimson (deep dark red) while rose madders tend to be bright pink, but we have encountered some very old oil paints marked Rose Madder which were the deep red shade.
