Firestain refers to a discoloration that appears on silver objects when the copper alloy in the silver reacts with heat during the crafting process. This oxidation shows up as dark, blotchy patches, often a purplish or reddish tint, and can be especially noticeable on older silver pieces. These stains are primarily caused by the formation of cuprous oxide—a compound that forms when copper in the alloy is exposed to heat and oxygen.

Firestaining is commonly found in silver items from the pre-colonial period through the early twentieth century. If you clean a solid silver piece and notice a purplish stain that doesn't come off, don’t mistake it for tarnish! Tarnish is a surface layer of silver sulfide, which forms in the presence of moisture or air, but firestain is related to the underlying copper content. Attempting to remove the firestain as you would tarnish can result in damage.

Why does this happen?

Silver used in jewelry and household objects isn’t pure silver; it’s an alloy of silver and copper. The copper helps make the silver stronger, but it also reacts to heat in ways that silver does not. When the piece is heated, such as during the crafting or soldering process, the copper oxidizes, leading to the characteristic purple or red stains. This is more likely to happen with older methods of silversmithing, particularly in smaller, one-person workshops where handmade techniques often result in more direct heat exposure.

Why is this only an issue in older pieces?

After the early 1900s, larger American silver manufacturers started using improved production methods that minimized firestaining. These methods might have involved using lower temperatures for soldering or employing more advanced techniques to shield the copper from excessive exposure to heat. However, smaller independent silversmiths still often use traditional methods that can lead to firestaining, even today.

What should you do if you find firestain on your object?

Nothing, firestain is a characteristic feature of some silver and should simply be appreciated as part of the objects patina.