Bouland,
It is obvious you never used theRomertopf pot I am referring to. These are not your sand pots, which you are right and you do not soak. Romertopfs are not even Chinese. They are just substitutes for the clay, just like the flour and paste are. The results seem to be the same.
As for as Caul fat is concerned, sometimes we have a time getting that in at school. Whenever that is ordered the market buyer has problems procuring it so it may not be a problem anyway.
Here are a set of instructions referring to the Romertopf clay pot that I got from a web site specializing in these pots.
"This special porous clay is unglazed, allowing it to breathe during the cooking process.
Food cooked in a clay pot requires no liquid unless specifically called for in a recipe. The result incorporates all-natural juices, the full flavor and taste, and all the essential nutrients and vitamins are retained.
You can cook all types of foods without adding any fat.
Directions
Before using the first time, wash thoroughly with hot water. Do not use soaps.
Before each time you use it, completely immerse the top and bottom in water for 10 to 15 minutes.
After adding all the ingredients, place your Romertopf in the center of a cold oven.
Do not add cold liquids once the Romertopf is hot.
Recipes usually can be converted for clay pots by increasing the cooking temperature by 100 degrees Fahrenheit, and deducting one-half hour of cooking time.
Romertopf is ideal for the microwave. Because microwave ovens vary to such a great degree, use the oven manufacturer's guidelines for cooking times.
To keep it in top condition for many, many years, take care not to shock it by moving it from one extreme temperature to another.
Use mitts or pot holders to move it when it is hot, and place it on a trivet, mat or folded dishtowel when moving it out of the oven.
Cleaning is a snap. Use hot water only, and a stiff natural bristle or nylon brush, or a nylon scouring pad to clean after each use. Do not use soaps; a little baking soda will cut any grease.
When not in use, keep the Romertopf in a place where the air circulates. Place lid upside down on top of base when storing, to allow air to circulate inside the bottom of the roaster.
Don't use the Romertopf on an open flame or hot cooking plate. It is designed for oven and microwave use only."
I hope this clarifies things for you.