The outer green glaze on these cone 6 porcelain mugs has a high melt fluidity. The liner glaze on the lower one, G2926B, is high gloss but not highly melt fluid. Notice that it forms a fairly crisp boundary with the outer glaze at the lip of the mug. The upper liner is G3806C, a fluid melt high gloss clear. The outer and inner glazes bleed together completely forming a very fuzzy boundary.
G3806C - Cone 6 Clear Fluid-Melt Clear Base Glaze
A base fluid-melt glaze recipe developed by Tony Hansen. With colorant additions it forms reactive melts that variegate and run. It is more resistant to crazing than others.
GR6-N - Ravenscrag Alberta Brilliant Cone 6 Celadon
Plainsman Cone 6 Ravenscrag Slip based glaze. It can be found among others at http://ravenscrag.com.
In ceramics, the edges of overglaze and underglaze color decoration often bleeds into the over or under glaze. How can this be avoided.
Fluid Melt Glazes
Fluid melt glazes and over-melting, over fired, to the point that they run down off ware. This feature enables the development of super-floss and cyrstallization.
How to Liner-Glaze a Mug
A step-by-step process to put a liner glaze in a mug that meets in a perfect line with the outside glaze at the rim.