Place a can of sweetened condensed milk, unopened (no need to remove labels) in the slow cooker. Add water to a level two inches above the cans. Add lid and cook for 10 hours on low.

As the cans cool, the moisture may cause them to leave a ring. Make sure to put them on a surface that won’t be damaged or on a several thicknesses of folded paper towel, a paper bag or old rag that you can be discarded.

Cool to room temperature before opening or storing. May be stored at room temperature, like all canned goods, in a cool, dark cupboard.