I've seen these tools before at ceramic supply stores, a little tiny rake for scoring pots. I've always used a serrated metal rib for scoring. When I went to StarWorks Ceramics for my weekly clay pick-up the other day, Takuro talked me into buying one. It's a great little tool. You can really score more thoroughly with it, and since a few of my two-piece foot-soaking bowls separated a bit at the joint during the glaze firing, I'm now being extra careful in joining the two pieces.
Here's the points I'm focusing on:
Adding grog and mullite to clay
Vinegar added to slurry
More deliberate tapping together the two pieces once joined
Watching that I don't use too much slip when adding coils inside and outside the joint
"Working" the joint as best as I can after outside coil is added (this is difficult as I'm adding an upside down bowl onto a platter at the leather hard stage)
I've decided to bisque fire all the pieces I made up until the ones I made today, so I'll have to fire every day to get 32 fired by the end of the month, my first deadline.
Here's a few pictures of today's work:
I'm cutting a groove into the outside of the bowl to allow a coil to be added outside the finished piece after joining.
Adding a coil on the outside
I do this after tapping the platter from underneath
with a metal chisel and then scoring and slipping
the groove. This is where I think I need to be careful
to not use too much slurry (or slip)