Pete Pinnell’s Terra Sigillata

Pete Pinnell’s Real Authentic Lip Smackin’ Smooth Easy Terra Sigillata
taken from Ceramic Arts Daily

Chanda’s note: I use grolleg as my dry clay, following the directions for XX Saggar. No soda ash is necessary.

In a 5 gallon bucket, put 28 pounds (28 pints or 31/2 gal.) of water.
Add 14 pounds dry clay. XX saggar works well for white base, RedArt for red.
Add enough sodium silicate to deflocculate (a few tablespoons).
For red clays use 2 teaspoons sodium silicate and 1 tablespoon soda ash.
Allow to settle. Overnight is average.
Less plastic red clays (such as RedArt or fire clay may require only 6-8 hours, while very plastic clays like XX Sagger or OM4 ball may take up to 48 hours).
Syphon off the top (this is the terra sig) without disturbing the sludgy mixture below.
Throw the rest away; do not reclaim.

Terra sig is best when the specific gravity is about 1.15.
Useful range is 1.1 – 1.2.
Specific gravity is measured by weighing out 100 grams of water, marking the volume, and weighing the same volume of the sig. Divide the weight of the sig by 100.

If too thin evaporate.
If too thick allow to settle longer.
Apply 2-3 thin coats sig to bone dry greenware and buff.

Pete uses “patinas” of 1 part gerstley borate + 1 part colorant as a thin wash over bisqued sigs, applied and rubbed off. Works on textured areas.

Color suggestions to 1 cup liquid terra sig:
white = + 1 tsp. Zircopax or tin
off white = + 1 tsp. titanium dioxide
green = + 1/2 tsp. chrome oxide
blue = + 1/2 tsp. cobalt carbonate
black = + 1 tsp. black stain
purple = + 1 tsp. crocus martis (in a white sig base)

Test batch weights & measures:
7 pints water
3.5 lb dry clay
2.5 grams sodium silicate
3.75 grams soda ash (if using a red clay)