Terra Sigillata (also called terra sig) is a way of creating a lovely smooth warm buttery finish on your pottery. 

Terra sigillata is a very refined clay slip that can be applied to the surface of your pot to create a high shine to your piece.   Because it is made out of the finest clay particles, it creates a very smooth finish.  

You can buy terra sigillata but it can be a little tricky to get hold of.  Fortunately, it’s reasonably easy to make.  If you’d like to know how to make terra sigillata, you can follow my step-by-step guide here. 

Applying Terra Sigillata

The best time to apply terra sigillata is to bone dry clay.  If you apply it to leather hard clay you can lose a bit of the shine from the finish.  The reason for this is that as your pottery continues to shrink it will create micro crinkles in the surface of the terra sigillata. 

Nice youtube on Terra Sigillata creating.

One way to apply terra sigillata is to position your pot on a pottery wheel or banding wheel.   Turn the wheel head and dip your mop brush into the terra sigillata.  Then apply the brush to the pot as the pot turns.  

Be careful not to overload your brush, as this can create drips on your pot which may cause streaks.   The terra sig will dry quickly on the bone dry clay. 

Once it’s touch dry you can apply another layer.  Usually, 3 layers are enough.  The more layers you add, the greater the chance that it will flake when you fire the clay.  

Once all three layers have been applied and are dry, you can buff the surface with a soft lint-free cloth.  This should bring the surface up to a high shine.  The pot can then be bisque fired to around 1823F (995C). 

The terra sigillata itself creates a lovely finish to your pots.  However, it can also make a nice smooth glossy base for other low fire ways of firing pottery such as raku firing or saggar firing.

Reference -  thepotterywheel.com -