I installed a mini beeper in my kiln and adjusted the software to beep letters in Morse code depending on the stage of the program. I just used the same transistor+resistor+5v supply design as for the SSD control line to prevent damage to the pi.
Roll of cake making acetate: use it to model PMC clay on and it comes off it easily once it has dried.
This is a “Kilner” type jar with some damp sponges cut to size in the base/top. The dampness keeps PMC clay from drying out solid while being stored for a while.
Tools for making marks in clay.
I had some old “Art Clay” copper clay that had dried out completely. I used this cheap coffee grinder to pulverise it so I could use it again. As this is metal powder, I didn’t want there to be any accidental confusion with it being re-used for food in future.
Dremel and steel/brass tools and brushes for burnishing metal post-kiln.
Welding gauntlets and welding goggles (these Uvex ones have protection from IR):
My steel firing box and associated metal tools for dealing with items at high temperatures. Some of these were from a cheap barbecue set.
“Laser” thermometer to check on temperature of cooling pieces prior to picking them up!
Some nail files from the local wee shop — for smoothing dried un-fired copper clay pieces.
Icing rolling pin for rolling out sheets of copper clay. It comes with little plastic bands you can put round it to achieve a desired thickness.
Recycled takeaway boxes for holding stuff temporarily (eg activated carbon, or water-filled quenching jars to prevent spillage).