The Caribou Ranch Stacker Mugs were made with the stacking function in mind, and were inspired by Japanese design.
A combined glaze aesthetic, Acero azul glaze on inside and top of outside with firing effects in concert with Bauer Slip application (slip is a liquid clay) are at work here.
In this case, the glazes and slip were applied to the piece before the first bisque firing.
Note that the slip shows the effects of soda, ash, and flame in the final firing and will be unique to each mug.
The base of each mug was textured prior to slip application.
As with all of Julie's work it is the third, phase, called "atmospheric firing" spanning roughly 30 hours plus cooling time, in which fire, heat, ash, and soda come together to create the final product. It is when, as Julie states the "kiln gods" are at work.