duco

To duco is to apply automotive lacquer paint to a vehicle body, typically by spray gun. The term originated in Australia and New Zealand in the mid-20th century, derived from the Duco brand of synthetic lacquer made by DuPont, which became the generic colloquialism for the process itself. Modern usage extends beyond the original DuPont product to any synthetic automotive paint application, though the verb retains regional strength in Commonwealth automotive trades.

Duco lacquers dry through solvent evaporation rather than chemical hardening, which made them revolutionary when introduced because they cured in hours instead of days. The paint consists of nitrocellulose dissolved in volatile organic compounds, typically thinned to spraying viscosity of 18 to 22 seconds in a Ford Cup viscometer. Application requires compressed air at 40 to 50 psi, proper spray technique to avoid runs and sags, and workshop conditions between 15 and 25 degrees Celsius with humidity below 85 percent.

The process demands multiple thin coats, each sanded between applications with 180 to 220 grit paper once dry. A full respray typically requires primer, two to three colour coats, and a clear coat or lacquer top layer for gloss and protection. The work is skilled: improper gun distance, speed, or overlap produces orange peel texture, dust nibs, or uneven colour.

Synthetic lacquers have largely been superseded in modern automotive manufacturing by polyurethane and waterborne acrylic systems, which offer better durability, lower environmental impact, and compliance with volatile organic compound regulations. However, duco remains common in panel beating shops, restoration work, and small independent spray operations, particularly in Australia and New Zealand where the term persists despite the chemistry changing beneath it.

The verb duco survives as a marker of practical automotive culture in regions where it took root. A panel beater might say 'we'll duco that panel tomorrow' without necessarily meaning the 1930s DuPont formulation. The term carries the weight of a specific tool and era, now used loosely to mean what it describes: painting a car body by spray.