Filling

Filling is the last moment the product is open, and every route a contaminant can take runs through it.

Filling is a contamination step

Everything the product touches between the mixing vessel and the closed container is a potential inoculation: the transfer vessel, the funnel, the filling nozzle, the air in the room, and hands.

The preservation system exists partly to cope with that, and there is no reason to spend its margin here. Sanitized equipment, clean containers, minimal open time, and hands that are either gloved or not in the product.

Viscosity decides the method

A thin serum pours and is easy. A thick cream does not, and forcing it produces air pockets and inaccurate fills.

The practical answer for a small operation is a piston filler for creams and a simple gravity or pump filler for thin products, and a scale under the container in either case so you are filling to weight rather than to a line. Weight is also what the label declares.

Headspace and fill level

Headspace is air, and air is oxidation and a reservoir for anything that got in. Less is better for the product and it fights with the customer's perception of a full jar.

For an oxygen-sensitive active this stops being a presentation question. An L-ascorbic acid serum with a large headspace is a serum with a shorter life, and it is one of the reasons airless packaging exists.

Sealing and what follows

Wipe the container rim before closing, because product on the land prevents a proper seal and, in an induction-sealed pack, prevents the bond entirely.

Then label, batch code every unit, and set aside retained samples from the beginning, middle and end of the run rather than from whichever jar is nearest. If the fill drifted, those three will show it.

References