The Ravenscrag Slip based burgundy glaze on the outside of these mugs is made by fluxing Ravenscrag with 20% Ferro Frit 3134 and adding 10% Mason 6006 burgundy stain (actually these have a little less stain, about 8%). This stain works better than using raw chrome and tin. This glaze functions very well on porcelains and breaks white on the edges to highlight contours.
Ravenscrag web site
GR6-E - Ravenscrag Cone 6 Raspberry Glossy
A chrome-tin burgundy glaze using the Ravenscrag cone 6 base recipe.