Like many potters, I use slip for various reasons in each temperature range I work in. I occasionally work in the Cone 5/6 range and have been using this slip, on and off since the early 90’s. I am not sure if I got it from Kirk Mangus or Bill Broulliard, but it has been an effective slip all these years on a wide variety of clay bodies.
Rudy Autio Slip Base (Cone 5/6)
Nepheline Syenite 12.5
Ball Clay 12.5 (I use Tenn #10)
Custer Spar 25
Kaolin 25
Flint 25
Zircopax 10 (this is for a white slip)
This is the clear glaze I have used on and off since about 1994. I am not sure where this FPC (Four Part Clear) came from, but it has been a very useful companion to the above slip recipe. I tend to use this glaze on the thinner side, though it also looks nice a bit thicker and rarely has running issues. With a few additions of colorants, it also makes a nice colored transparent glaze.
FPC (Cone 5/6)
Gerstley Borate 25
Spodumene 25
Custer Spar 25
Flint 25
Illustrated is a black slipped teabowl made back when I was in Cleveland using these two formulas.