Is it all right to clean dirty surface coins with soapy water and wipe dry with a soft rag?

1. It is best to use distilled water. Minerals in your tap water may react with the metal. 2. Use SOAP, not DETERGENT. Again, chemicals may affect the coin surface. 3. Let the coins soak to loosen the surface dirt then gently sweep it off with an artist's camel hair brush. 4. Allow to air-dry laying on the soft cloth, but don't wipe them.

If additional cleaning is needed, it should be done by an expert conservator.