whitening

Whitening refers to processes that make something whiter or remove color or impurities to achieve a whitened appearance. The term covers literal whitening of materials as well as specialized uses in industry, cosmetics, and science.

In industrial contexts, whitening or bleaching involves breaking down chromophores—color-containing compounds—using oxidizing agents. Historically chlorine-based bleaches such as calcium hypochlorite were common, but modern practice relies on hydrogen peroxide, sodium hypochlorite at controlled conditions, and peracids. Some systems add optical brighteners to enhance perceived whiteness without removing color.

In textiles and pulp and paper, whitening improves the brightness of fabrics, fibers, and paper products. If not carefully managed, chemical bleaching can produce environmental byproducts and affect fiber strength.

Teeth whitening is a dental procedure that reduces intrinsic stains on enamel. Agents typically contain peroxide (carbamide or hydrogen peroxide) delivered in gels, strips, or trays. Professional treatments generally use higher concentrations. Efficacy varies by stain type and baseline color; risks include temporary tooth sensitivity and gum irritation; results may require ongoing maintenance and do not affect restorations such as fillings or crowns.

Skin whitening or lightening refers to products aimed at reducing melanin or inhibiting its production. Agents include hydroquinone, kojic acid, azelaic acid, arbutin, and vitamin C. Use is regulated differently by country; safety concerns include irritation and, with long-term hydroquinone use, potential ochronosis and other adverse effects. The topic is controversial due to ethical considerations and social implications.

In data processing and signal processing, whitening denotes transforming data to remove correlations and equalize variances, aiding subsequent analysis or modeling.