Bread and Butter Pickles
Use a large stainless steel pot or a large glass bowl. Add cucumbers and sliced onions. Add 2 tsp. salt over the top and cover everything with cold water. Let stand for 1 hour in the saltwater. Drain off the water.
In a saucepan, add the vinegar, sugar, celery seed, 2 tsp. salt and the mustard seed. Stir over medium heat and bring it to a boil.
In a large cookpot (5-6 quarts), add the cucumbers and onions, and pour the heated vinegar mixture over the top. Cook for 20 minutes, stirring with a spoon.
Put pint jars in the oven on the racks and set temp. to 200 degrees. Take the jar lids and rings and cover them with water in a saucepan--bring them to a boil. Put cucumbers/onions/juice in each jar until you run out of the mixture. Take a table knife and insert it all around the sides and middle of the jars to get the air bubbles out. Put the ring and center piece on each jar and turn tightly. Put the jars on a surface that can safely stand heat. Let them cool and as they cool they will seal themselves. If the jars seal properly, they will last about 2 years.
Once you open a jar, refrigerate it.