substanceCertain ClayColors & materialsA named craft material / finish lemma (Certain Clay) drawn as an exact public-domain workshop phrase.Certain Clay is historically related to Clay.earth-colours seats orphan certain-clay beside clay as a first craft peer — object speech, not a text-container or tradition dump.from Josef Bersch · The Manufacture of Earth Colours, PD Gutenberg #71219historically related to · sourced · documentedsourcesThe Manufacture of Earth Colours · Josef BerschBersch, The Manufacture of Earth Colours (PD Gutenberg ed.).