In 2015 I documented a project comparing common cone 6 fluid-melt base glazes, picked a favourite (Panama Blue) and over-hauled the recipe to fix it's slurry issues and serious crazing. While fluid-melts almost run off ware when applied thick, they host stains & opacifiers to produce brilliant super-gloss surfaces. But the typical chemistry of these is susceptible to crazing, scratching and leaching. In 2019 I reformulated again, moving the thermal expansion down from 7.3 to an incredible 5.8 (the base can now survive a 325F-to-icewater test on our toughest-to-fit porcelain with no crazing). And it is melt-fluidity-controllable, durable (having 30%+ more Al2O3/SiO2) and sources Li2O, MgO and KNaO from frits. Follow the link here to see the entire history of this development effort (beware, there are multiple pages, each with many columns).
2019 Development of G3806 melt-fluid low-expansion clear base glaze
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.