The original glaze without phosphorus.

This is satiny silver with dark oil spots and a brown rim.

The metallic surface crystals form a thin surface layer, which is absent in a thin glaze application.
If broken, a layer of metallic silver atop a thick glossy brown substrate is seen in the cross section of the pot wall.

bowl is ~3 inches in diameter

Glaze mashiko_ZJ_PP_Z2A

glaze containing phosphorus.

The surface is a varigated splatter of iron colors, while the volcanic erruptions just prior to maturation produced the silvery oil spots.
These are a remnant of the metallic surface crystals of the above glaze, mashiko_ZS_T_5. The late boiling created differential flow within the glaze
and segregation of the glaze components, thus the eccentric scattering of colors.

Dependant on the lighting, there is a distinct hint of lusterous opalescence which contributes to the multicolored effect.

The silvery oil spot glaze family, of which mashiko_ZS_T_5 is a member mature precipitously, in a small temperature window.
The glazes are reacting rapidly near maturation, these chemical reactions involve boiling, thus the oil spots.

Phosphorus being a glass former, likely raises the temperature at which the chemical reactions finish, and the glaze settles down
with a smooth surface. The result, mashiko_ZJ_PP_Z2A didn't quite finish settling down.

mug is ~5 inches in high

oxidation firing to cone 10 in an electric kiln

glaze compositions