Gravimetric Feeding in Cosmetics Production

A colour cosmetic recipe is a base of talc, mica or calcium carbonate with pigments at a fraction of a percent, and the ratio between those pigments sets the shade. The tolerance is whatever a trained eye accepts against a standard, which is tighter than most analytical specifications.

That puts the whole burden on small feeders handling difficult materials. Pigments are fine, cohesive, often agglomerated, and they have a low and variable bulk density, which is the worst combination for a volumetric relationship.

They also stain. Iron oxides and organic lakes mark every surface they touch, and a feeder that held a dark pigment yesterday will give up traces of it today unless it has been stripped. The contamination is not analytical; it is visible in the pressed product.

And the quantities are small enough that the feeder is often oversized simply because small feeders look unserious next to the mixer. The datasheet accuracy then describes a rate nobody is using.

In cosmetics manufacturing the tolerance is a visible one: a shade that drifts is a reject even when the recipe stayed inside its stated limits.

Pigment feeders sized for the actual gram scale rates, with accuracy stated at those rates and verified by catch tests with the pigment itself.

Machines that strip quickly and completely, so a shade change is a cleaning operation that finishes inside the changeover window and can be signed off visually.

Pigment contained at charging, feeding and cleaning, with exposure controlled and the room kept out of the next batch.

In food production the same mistake takes a different shape: one feeder size for a recipe set spanning three orders of magnitude, accurate at the top and blind at the bottom.

Feeder sizing starts from the smallest pigment rate in the shade range, not from the batch size. Small twin screw feeders handle cohesive pigments; where the rate is very low, a feeder with a reduced screw and a slow drive holds a better factor than a larger machine at the bottom of its range.

Hopper design follows the material. Steep walls, flexible sections with external massage, and agitation kept to the minimum that maintains flow, since working a pigment aerates it and moves the feed factor.

Changeover drives the construction. Quick release hopper, screw and tube, no internal ledge, and a design that can be inspected visually, because the sign off for a shade change is somebody looking at the inside of the machine. Dedicated screws and tubes per pigment family are common and usually cheaper than the cleaning they replace.

Containment is designed around charging and cleaning, which is where pigment escapes. Enclosed charging, extraction at the point of work and a clean down method that does not blow powder around; several of these pigments also have occupational exposure limits that make this a duty rather than a preference.

• Pigment feeders sized from the smallest rate in the shade range.
• Accuracy verified by catch tests with the actual pigment, not from a datasheet.
• Hopper designed for flow, with agitation limited to avoid aerating the pigment.
• Quick release contact parts, no internal ledges, and full visual inspection access.
• Dedicated screws and tubes per pigment family where changeover frequency is high.
• Enclosed charging and extraction at cleaning, with exposure limits respected.

• Smallest pigment rate in the shade range, which sets the feeder size.
• Shade tolerance and how it is assessed, usually visually and therefore tightly.
• Pigment flow behaviour and bulk density variability.
• Changeover frequency between shades, which decides cleaning versus dedicated parts.
• Staining and exposure, which set the containment requirement.
• Batch size range, including the smallest batch the line has to make accurately.