What is tarnishing silverware?

Answer 1

If by "silverware" you mean "eating utensils" then yes, there was, but it was not quite the same as what we use today.

If you literally mean eating utensils made of actual silver, then again, yes, but it was vanishingly rare.

Nearly every medieval person carried a small personal knife (a fact that is joked about the movie "The Lion in Winter"). This knife was the primary eating utensil, used not only for cutting but also much the same way we use forks.

Spoons were fairly common, but again not really the same way we use them for practically everything. Soups were generally drunk out of the "mazers" (a large, wide mouthed cup, similiar to what lattes are served in today, but without the handle). Spoons for daily use were made of wood or cowhorn, but metal spoons were considered heriloom items and start showing up in English wills in the 13th century.

Forks were also known, but used primarily by cooks, not by those eating. These generally only had 2 prongs.

Matched silverware sets were a fashion that began in 16th century Italy, but really didn't take off until they became the court fashion of 17th century France.

Therefore, a typical table setting in the high middle ages consisted mostly of the table linens, plates (or trenchers) and mazers. Guest were expected to have thier own knife (in fact, it would have been considered declasse to eat off someone else's knife) and spoon, if they used a spoon.

Answer 2

Oxidation from air

Answer 3

Table ware with a silver coating.