[header] How to clean a cast iron sink [title] Mix water and dishwashing soap together in a 5-gallon (18. 92 l) bucket. [step] Mix 1 gallon (3.78 l) of hot water with 2 tablespoons (29.57 ml) of dishwashing soap. Look for a dishwashing liquid that has a grease cutting agent in it and a scent that you like. 
[title] Wipe down the sink with a sponge or rag. [step] Dip a sponge or rag into the water and soap solution that you created.