So I stumbled across a technique that is used by some Potters in Mexico that I want to try. So I am doing that now. The technique is to apply graphite to bone dry pottery, and then burnish the piece. The result when fired is a shiny deep black surface on your piece. I have only run across to discussions about how this is done.
In the pics below, the first I have started applying the graphite to this plate and burnishing the outside edge. The second pick is on un-modified surface of my bone dry terra-cotta plate. And third pic I am finished burnishing.
In the workshop video I have watched about this, the Mexican potter that was doing itExplained how the pieces were finally sanded before applying the graphite. And this application of graphite and burnishing is done three times. The process is very time-consuming, Slow. And usually only one piece is produced a week. However the results are amazing. As you can see below. On this piece i did not sand, and I have only applied the process once thus far.