T. considers as the primary flow that portion of the glassmelting which is ready to be shaped into various products 10 to 15hr. after that portion of the charge has been loaded into the tank furnace. The characteristics of the primary flow were studied from the distribution of coloration in the drawn-out sheets of glass. This method is preferred to that requiring the addition of the BaO because it requires no chemical analysis and makes it possible to observe the flow and distribution characteristics of the primary melt from that moment of its appearance to the withdrawal of the sheet. Primary glass melt was observed in the sheets of the central Fourcault machines 10 to 12hr after the appearance of coloured glass melt in the tank furnace and 4 to 6 hr later it was observed in sheets of those following the central machines.
