What is Instrument Staining?
Staining is a surface deposit on instruments, and most often mistaken for rust. After autoclaving, you may notice a stain on your instruments. Rusting instruments are very rare, especially when you purchase high quality German or USI brand instruments. Stains on instruments appear in many colors and in most cases the colors tell you about the origin of the stain.
The problem is most often a phosphate layer (brown to light orange) on the instrument, which develops as a result of any of the following causes: water sources, detergents used to wash and clean instruments, surgical wrappings, cold sterilization solutions, or dried blood.
The most common black stains are due to an acid reaction. Black stains may result from detergents used to clean the instrument; similar to brown stains caused by high pH detergents. The black acid type stain can be caused by low pH (less than six) during autoclaving.
Dark Brown Stain
Dark brown stains are usually a result of dried blood left on an instrument. Blood should be removed from the surface of the instrument immediately. It will break down the instruments surface chemical reaction.
These are usually a result of plating and are extremely difficult to remove from the surface. The surface beneath the stain is always smooth, but the instrument may have to be refinished to obtain good results. The cause for this stain is the mixing of dissimilar metals in ultrasonic cleaners and during autoclaving. Multi-color stains are most often due to excessive heat (chromium oxide stains) and actually show rainbow colors with a blue or brown overtone. When the instrument shows these heat stains, it may have lost pert of its original hardness, and may not perform well.