|Monthly Tech-Tip |
The dipping glaze version of G2917 was used on the left, we make that by the bucket and it drains and dries in seconds after dipping bisque ware. We also make a brushing glaze version in our studio (it is not sold). That was used on the outside of the mug on the right. Of course, it is much slower to apply but there are some advantages. First, it was easy to control the thickness to maximize the variegation this glaze gives with thin and thick, revealing the throwing lines better. And where thicker application was needed (e.g. at the rim) it was easier to achieve that. Near the foot ring, it has been applied in a thinner layer. And the brush strokes do impart a more handmade look that is also nice.
These are GA6-C Alberta Slip floating blue (left), AMACO Potter's Choice PC-20 Blue Rutile (center), GR6-M Ravenscrag floating blue (right). The clay is M390. The firing is cone 6, the schedule is C6DHSC (drop-and-hold, slow cool). All of these recipes are descendants and improvements of the 50-year-old original G2826R floating blue. The inside glaze on these mugs is GA6-B. The two on the left develop the blue color because of the slow cool, the one on the right works on fast-cool because it contains cobalt (although it will fire somewhat more mottled). Remember, these work best on dark-burning bodies.
A popular cone 6 glaze that employed Gerstley Borate, it was very troublesome to use and to fire. Much work has been done to create alternative recipes.