fondu

A fondu is a gradual, imperceptible shift from one ink color to another across a printed surface. In offset and flexographic printing, it creates the visual effect of one hue melting into the next without a visible boundary line. The transition can span millimeters or several centimeters, depending on the design intent and the printing process parameters.

The fondu is achieved by adjusting ink fountain settings on the press, typically using fountain keys or zone controls that meter different ink densities across the print width. On some presses, the operator gradually reduces ink flow in one color zone while simultaneously increasing it in an adjacent zone. The actual blending occurs in the print nip, where paper or substrate compresses momentarily against the printing plate or roller, allowing inks to merge slightly at their interface.

Variants and application

Fondus appear frequently in packaging design, label printing, and decorative applications where a photographic or artistic effect is desired without the cost of full-color process printing. They are more common in flexographic printing than offset, since flexo's softer kiss impression allows inks to blend more naturally. The technique is also used in gravure printing, where cylinder engraving depth itself creates the gradation.

The main technical challenge is consistency across the print run. Temperature changes in the ink, variations in substrate tension, and wear on fountain keys all shift the fondu's position and smoothness. Operators must monitor early printed sheets closely and make small, frequent adjustments to fountain settings rather than large corrections. A fondu that is too abrupt reads as a registration error; one that is too diffuse may look muddy or lose intended color definition.

The term derives from the French word for 'melted' or 'blended', reflecting the visual appearance. In French and some European printing traditions, the term remains standard; North American printers sometimes call the same effect a fade or blend, though fondu persists in technical literature and among experienced press operators.