Red oil

Meaning

Something like red oil floating above the matter is called a very bad sign in the material fault-list. The wording is comparative: it looks like red oil, rather than being identified by a chemical analysis. Its untimely appearance belongs with premature rising before dissolution and blackness. Red is therefore not invariably a successful endpoint. The same list separately warns against redness arriving too soon, making order and timing indispensable to interpretation. This entry records the diagnostic role without recommending any attempt to produce or correct the appearance.