I have an old silver spoon which I keep in a drawer with other cutlery and utensils. I recently took it out and saw that the bottom of the bowl had developed an interesting pattern, presumably caused by a chemical reaction (see photos). What caused this? The spoon was in a drawer with stainless steel cutlery and also with utensils of other metals. Plastic and wood could also have come into contact with any of these.
Valerie Cumming, Stafford, UK