I use colored terra sigillata instead of underglaze for the inlaying technique. The final firing is too high to see any sheen, but I do like the matte surface it creates. I found the colored terra sigillata and complementary underglaze to fill in the designs is the perfect combination. I apply the terra sigillata at the leather-hard stage rather than bone dry, so I am still able to carve through the surface.
There are so many ways to make terra sigillata and I have found that this simple method works best for me. It takes less than 10 minutes to make and utilizes a 2-liter water bottle in place of a big bucket. I leave it to sit undisturbed longer than other recipes so a thicker terra sigillata is generated. I usually end up with 0.6 liters and that’s enough to last 6 months.
With an empty 2-liter water bottle, add the following ingredients:
1 liter of water
500g of ball clay
The following premixed: 1.25g sodium silicate, 1.25g of soda ash, and 2.5g of hot water
Mix these well by shaking the bottle, then leave it for a few days without disruption. Following the resting period, you should see 3 distinct layers: larger particles on the bottom, the finer-particle terra sigillata layer in the middle, and a clear water layer on top. Puncture a hole above the lowest layer at the beginning/bottom of terra sigillata layer and let that drip into another container. The terra sigillata will flow out naturally.
To color the terra sigillata, add /- 1% oxides or /- 5% stain.
This recipe was shared by Miae Kin in the November/December 2023 issue of Pottery Making Illustrated.