fixative

A fixative is a substance used to stabilize, preserve, or immobilize materials by preventing decay, movement, or distortion. The term is used in several fields, including biology and medicine, art, and perfumery, where the goal is to keep a material in its original state for analysis, display, or use.

In histology and pathology, fixatives preserve tissue by immobilizing and cross-linking proteins, inactivating enzymes, and killing microorganisms. The most widely used fixative is formaldehyde, typically prepared as neutral buffered formalin. Other common fixatives include glutaraldehyde, methanol, and ethanol. Fixation conditions—time, temperature, and concentration—affect tissue morphology and the accessibility of antigens for staining. Some fixatives introduce cross-linking that can hinder molecular analyses, requiring antigen retrieval or alternative methods.

In art and conservation, fixatives are coatings applied to drawings made with charcoal, pastel, or graphite to prevent smudging and to preserve finished works. Traditional fixatives include gum arabic and resin-based solutions; modern formulations may use acrylic or polyurethane binders. The choice depends on media, desired reversibility, and aging properties.

In perfumery and cosmetics, fixatives slow the evaporation of volatile fragrance components, helping to stabilize and extend scent lifetimes on the skin or in products. Fixatives can be natural resins or essential oil–derived compounds, as well as synthetic molecules designed to increase the duration of fragrance notes.

Other specialized uses include fixatives for photography, microbiology, and forensic science, where they stabilize samples, preserve evidence, or help archiving. Across fields, the effectiveness of a fixative depends on compatibility with the material and the intended analysis or display.