Baking soda is used to neutralize sulfur lever, which prevents your work piece from becoming darker than you want. It is better for the skin that you neutralize the sulfur residue.
Before you start blacking with sulfur, prepare a mixture of baking soda and water so that you can stop the color change when the desired color is reached.
In a container, mix about one part of baking soda with sixteen parts of water. Use a container large enough to immerse the copper or silver object. Leave it for a few minutes and take it out and wash the item with warm water and soap.
Baking salt can also be added to the sulfur solution after you have finished. The baking soda neutralizes the sulfur liver and Blits-beits, so you can safely wash it away in the sink.