The Cone 4/6 Floating Glazes are all lead-free and dinnerware safe.  They require 2-3 coats for full coverage.  Floating glazes is in no way a technical term. 
This series is named after its appearance where one color appears to float above the other without requiring the need to layer multiple glazes together.
Samples are at Cone 5 and changes in temperature can produce variations on the appearance.