Everyone has their own methods for cleaning cast iron. My style is a combination of the methods of others and a little trial and experimentation of my own (this is why I'm a scientist, I guess). The method below can be used for black cast iron, nickel or chrome coated iron, but NOT porcelein coated or aluminum. I use lye (Red Devil) and water. I have a 50 gallon heavy duty barrel that I cut in half. This way I can handle the LARGEST pieces, PLUS additional pieces at the same time. Lye is environmentally safe, but very dangerous/caustic and must be used with care. Keep away from small children and animals/pets. NEVER NEVER NEVER add water onto lye. ALWAYS ALWAYS add lye to water. It may not seem important, BUT IT IS. The reaction of lye with water is exothermic (in other words, very violet and hot). It can get so hot that it will boil. So remember, respect the lye and add lye to water. The solution will feel "soapy" when you have a good "working" solution, BUT, if the solution comes in contact with the eyes or skin, it must be washed off immediately. This stuff will "eat" your clothes and skin. Always wear eye protection and where rubber gloves (I use dishwashing gloves). As a safety precaution, the container should be covered. This will prevent evaporation, minimize the chances of spills, and protect against foreign objects from falling into the vat. The lye wash can be used for more than one "batch" of cleaning. In fact, the water will turn REALLY black and I've never changed my water, just add more lye once it "stops working". The following instructions must be used with caution and at your own risk. I provide this as information only.
Lye Wash Cleaning Method:
Soak cast iron pieces in lye water. Mix 1 can of lye (i.e., Red Devil) with 4-5 gallons of water in a plastic container. Suspend pieces utilizing steel coat hangers. Usually several days to a week for really dirty pieces will be enough. I have left pieces in the tub for months (yes, months) and they do not rust and are not damaged by this method.
Remove pieces after soaking and rinse with hose and relatively high water pressure. If grease does not wash away, try wiping with stainless steel souring pad or brush. Repeat the lye bath as required.
After piece(s) are dry, brush with fine steel brush on drill or wire wheel.
Repeat the lye bath if necessary.
Wash the piece in dishwashing soap and warm water and rinse thoroughly. Dry. You can speed the drying by placing in the oven at 200 degrees.
Apply mineral oil, generously, completely coating the item. Let stand overnight.
Wipe off excess oil with paper towel and buff with a soft cloth
LYE does not remove rust, do the following:
Soak pieces in solution of 50% white vinegar and 50% water for several hours. Now this will depend on each piece, BUT remember vinegar is an acid and acids EAT metal You will ruin your piece if you let it in the bath too long. This is NOT like the lye bath.
Remove from vinegar solution, rinse and rub/brush to determine if rust has been removed. Repeat vinegar bath if required.
Dry, oil, wipe, buff as above.