To rinse the inside, place the casings in a colander in the sink. Run a stream of 90 degrees F (32 degrees C) into the sink. Find an end of one of the casings, hold it open under the running water, and fill with 8 to 10 inches of water. Gently lift the casing out of the colander, allowing the water to run all the way through to empty out the end. Repeat twice more, and set aside; do the same with the remaining casings.