Glossary · Trade
Bluing
Heat-tempering steel parts to a deep blue for hardness control and decoration.
Explanation
Bluing is the controlled oxidation that gives steel screws and hands their deep blue colour and a thin protective oxide layer. Traditional thermal bluing heats the part over a flame or on a bluing pan to roughly 290–310°C; chemical bluing uses salts. Even, deep blue screws are a sign of careful finishing — and of careful restoration, since screws are often re-blued.
In the object catalogue
Catalogued objects whose own source record mentions “Bluing”. The quoted line shows where; it is the seller’s or museum’s wording, not independent verification.
