[30] “The best of all blacks, which can be spread the best and with which one can even glaze, is ivory black, or that prepared from the foot bones of sheep. These, in pieces, are put in a crucible, which is well covered with a brick and the seams tightly sealed so that no air can penetrate, and put the whole thing on a strong fire, not longer than an hour, (otherwise the bones will bleach) and thus the mass is burned to a perfect black.” This quote refers to the preparation of sheep bone black for oil paint, but since the preparation method is the same for pigments for watercolors it is included here. In: Mayerne. 1620-46. Mayerne Manuscript, London, British Library, MS Sloane 2052: folio 93r. https://www.bl.uk/manuscripts/Viewer.aspx?ref=sloane_ms_2052_f93r (transl. in Fels, Donald C., Lost Secrets of Flemish Painting: Including the First Complete English Translation of the De Mayerne Manuscript, B.M. Sloane 2052. Rev. ed. Floyd (VA): Alchemist, ed. 2010.