I’m often asked about my surfaces and it’s usually not a simple answer. My explanation usually winds up taking a few minutes because I often use a blend of several techniques to achieve the look I’m after, including but not limited to colored terra sigillata, commercial underglaze, glaze, and even multiple firings. Below you'll find some info on terra sigs I use as well as some glaze tweaking hints. Hope it helps some of you out!

Terra Sigillata Mason Jars

I use Pete Pinnell's Terra Sig Recipe (listed below), but I tweak a few things. I let clay settle for only 24 hours (white sig) and siphon the middle layer. I then measure the specific gravity (details below). If the sig is too watery I might need to evaporate some water from the sig, so I typically just leave the lid off for a few days, making sure to check back with it.

I prefer my sigs to be the consistency of 2% milk. Not totally thinned out, but I don't want them thick like whole milk. I want to apply sig onto my bone dry surfaces and coat the piece in several thin coats.

PETE PINNELL’S TERRA SIGILLATA

Pete Pinnell’s Real Authentic Lip Smackin’ Smooth Easy Terra Sigillata

Large Batch Recipe

  1. In a 5 gallon bucket, put 28 pounds (28 pints or 31/2 gal.) of water.

  2. Add 14 pounds dry clay. XX sagger works well for white base, RedArt for red.

  3. Add enough sodium silicate to deflocculate (a few tablespoons). *For red clays use 2 teaspoons sodium silicate and 1 tablespoon soda ash.

  4. Allow settling. 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).

  5. Siphon off the top (this is the terra sig) without disturbing the sludgy mixture below.
    Throw the rest away; do not reclaim.

Circular Test Tiles Ben Roti
Aardvark Obsidian Test Tile
Glass Mason Jars

Small Batch Recipe

XX SAGGER TERRA SIG RECIPE

  • Water               3000 grams

  • XX Sagger        1500 grams

  • Deflocculant   25 grams (sodium silicate)

Specific Gravity

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.

  • Terra sig is best when the specific gravity is about 1.15.

  • The useful range is 1.1 – 1.2.

If too thin evaporate.
If too thick allow it to settle longer.

COLORANTS

Start with a white base and add stains or oxides to create a palette of your own. You can add more than one stain to the white sig base. The combinations are endless.

I use 1 tsp. of stain to 1/2 cup of sig. The color and sheen of the sig will be affected by the end firing temperature. Generally, stick to Pete Pinnell’s rule of no more than 3 teaspoons of colorant per 1 cup of terra sigillata base

Marjon Mason Stains

My white sigillata base recipes:
(All colors are added to 1 cup of white sig)

  • Orange = 3 teaspoons #6028

  • Yellow = 3 teaspoons #6433

  • Blue = 3 teaspoons 6376 or 6315

  • Red = 5 teaspoons Bright Red

  • Green = 3 teaspoons Evergreen

  • Grey = 1/2 teaspoon #6600

Other 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)

Ben Roti Terra Sigillata

APPLICATION

I apply terra sigillata to my wares at the bone dry state.  I typically use the terra sigillata as a vehicle for color that I will eventually apply underglaze on top of after the bisque firing. I brush three very thin coats with a soft moppy brush.  For a soft sheen, I burnish the sig with a plastic grocery bag stretched over my finger before it completely dries.  Work in small sections around the piece.