If the crockery insert of a slow cooker develops a surface crack, there's an old-fashioned remedy to keep the crack from getting worse. There is no safe way to repair a Crock Pot that's cracked into multiple pieces at home, as no easily available glues are food safe at the heat that a slow cooker maintains while in use. But where glues fail, hot milk can fill a surface crack and create a bond that will last for a long time.
Wash and dry the crockery insert thoroughly. Identify the location and size of the crack so you know where to check after the repair. If the crack is higher up the side of the crock than the sides of your deepest roasting pan, use a large canning pot and more milk to make sure the crack is covered by the liquid.
Fill the roasting pan or canning pot with cool water up to the halfway mark. Pour the water back into a measuring cup to determine the capacity of the pan. This is the amount of milk you need to use for the repair.
Pour a measure of milk equal to the capacity of the large pan into a saucepan. Bring the milk to a simmer but do not let it boil.
Remove the saucepan from the stove and set the roasting pan or canning pot on a burner. Turn the burner to medium and pour in half the milk. Set the slow cooker insert into the center of the roasting pan or pot and pour the rest of the milk into the bowl of the insert.
Bring the milk to a boil and let it bubble for about 20 minutes. Turn off the stove and allow the milk and the crock to cool off naturally. When the crockery is cool to the touch, pour out the milk and wash the insert.
Test the strength of the repair by heating a quart or two of water in the slow cooker to be sure that the repaired crack is watertight.
If this repair method doesn't work, many slow cooker manufacturers sell replacement crockery inserts.