I follow the blog of a fellow model maker who lives in London. His hobby is "mud larking". That means he explores the shorelines of the Thames and other rivers looking for interesting and ancient artifacts that turn up in the muddy banks of the river. As part of my interest in old buildings from that area of the world I enjoy reading about how things were done in that time, not just structures but also the contents of buildings and methods of work including domestic. Recently I helped him identify some round disc shaped objects that had a hole in the middle as being drop spindle whorls used for hand spinning fibers into yarn.
So he sent me another mystery to solve. A photo of a number of slightly over 1 inch in diameter ceramic balls that he keeps finding in one location. My answer back was had he ever heard of the story of "stone soup"? The tale is about being so poor that there is nothing of substance in the soup other than stones. Being modern we are at a disconnect as to why people would have such a tale. But in actuality the stones were put into ceramic pots to provide the heat for slow cooking. Then of course the pots were put into some type of insulation such as nested into a box of straw. Now we have people making insulated blankets for slow cooking. However those makers of the cookers don't realize that there should also be a long lasting heat holding source inside of the pots for the most effective cooking of the contents, stones or what they evolved into, reusable ceramic balls. These ceramic cooking balls have been found in archeological digs around the world including the digs at James Town in the USA, keywords "cook stone cuisine". I guess you could have a potter make you some if you want to use an insulated slow cooker pot. They will help things cook faster and stay hot longer than just pre-warming the food and the pot. Of course they should be removed before serving the meal and also be larger than 1 inch so that they are readily visible and not bitten into if one is overlooked before serving. What is an old way of cooking can become new again
The photo of the ceramic balls my mud larking friend found on the bank of the Thames.