substanceProduct OxideColors & materialsA named craft material / finish lemma (Product Oxide) drawn as an exact public-domain workshop phrase.Product Oxide is historically related to Salt.earth-colours seats orphan product-oxide beside salt 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.).