distributor

In a printing press, the distributor is a roller or set of rollers whose sole job is to take ink from the supply and spread it into a thin, even film across the press. It sits between the ink fountain and the forme rollers, acting as the middleman in the ink delivery system. Without proper distribution, ink reaches the printing surface in clumps and thin patches, producing spotted or faded impressions.

Most offset and letterpress machines use multiple distributors working in series. A typical setup has one or two large distributors (sometimes called form rollers or ductor rollers) that receive ink from the fountain roller, then pass it to smaller distributors that work across the width of the press. Each distributor rotates against its neighbor at a slight angle, splitting and re-combining the ink film with each pass. This cross-hatching action breaks up pigment clusters and ensures uniform viscosity and coverage before ink reaches the forme or blanket.

The surface of a distributor matters enormously. Traditional distributors have hard rubber or composition sleeves; modern ones may use synthetic compounds chosen for specific ink types and viscosities. A worn or glazed distributor surface (where the rubber has become slick or hard) stops distributing properly and causes streaky prints. Regular cleaning with appropriate solvents and occasional re-surfacing keep distributors performing.

Distributor speed and pressure are critical variables. Too much pressure against the next roller creates heat and can damage the rubber sleeve; too little leaves ink unevenly applied. Speed ratios between distributors and the forme rollers determine how many times ink gets worked before printing. Different jobs and ink formulations demand different settings, which is why adjusting the distribution system is one of the first steps in setting up a press for a new job.

The term distributor is sometimes used loosely to mean any ink-carrying roller, but technically it refers to the rollers that perform the distribution function specifically, not the ductor roller (which portions ink from the fountain) or the forme roller (which applies ink to the plate or type). Understanding which roller is which matters when diagnosing print quality problems or ordering replacement sleeves.