This is decorating slip. Please follow this link for casting
Clay Potter's Slip 10% off
Slip trailing can be used to create patterns, show
decorative skills of the potter, or personalize items. Potter's
slip can be successfully applied to a wide variety of clay bodies
ranging from cone 06 to cone 8. Shake well before using to
activate the deflocculant and provide good fluidity, then perforate the
tip of the bottle using a needle.
Holding your slip trailer bottle
upside down with the cap on, shake the slip so that it fills the tip end
of the bottle to minimize air bubbles that might cause a break in the
slip trailed line. Apply to moist clay for a raised line.
Potter's slip may also be brushed on at any stage, but it will need to
be thinned with water. 4 oz Bottles and Pint Jars. Samples
below were fired at cone 05 on White Earthenware