This is the basic inlay slip recipe suggested by Steven Young Lee in his March 2010 article for Ceramic Arts Daily. The only difference is the 1:1 substitution of Glomax (a commercial calcinated kaolin) for the XX Sagger Clay originally in the article.
25 XX Sagger Clay or calcinated kaolin
15 Nepheline syenite
15 325 Flint
4 Cobalt oxide
4 Manganese dioxide
6 Red iron oxide
2 Chrome oxide
I'm using this recipe as my base slip for exploring bisque fired line inlay this fall.