Net weight drifting between jars

Twenty jars off the same batch, and weighed afterwards they span a range you would rather not put on a label. Spice is harder to fill accurately than almost anything else its size, and the reasons are physical rather than careless.

Why it is a labeling problem

The principal display panel has to bear a declaration of net quantity of contents, and where that is expressed by weight the term is net weight. That is a statement about what is in that jar, not an average across your batch.

So drift is not a yield inefficiency you can absorb. It is a claim on every unit, and underfill is the direction that matters.

What makes spice hard to fill

Low bulk density means a small weight occupies a large and variable volume, so volumetric filling is inherently imprecise. Leaf material bridges and clings. Static makes fine powder stick to funnels and jar walls. And bulk density itself shifts with grind and with how compacted the source container was.

A scoop that was right this morning is not right after the bin has settled.

Settling is not loss

Worth separating, because they get confused. A jar that looks less full after shipping has not lost weight; the powder has consolidated. That is settling, and regulation explicitly recognizes unavoidable settling as functional slack-fill.

A jar that weighs less than the label says is a different and more serious matter. One is an appearance question, the other is a compliance question.

Controlling it

Fill to weight, not to volume. A bench scale under the jar during filling removes the entire class of problem and is the cheapest equipment upgrade in the operation.

Check-weigh a sample from every batch and write it down. Set your target slightly above the declared weight rather than exactly on it, because the distribution has two tails and only one of them is a problem. And re-check the target whenever the grind changes, because the same scoop is now delivering a different mass.

References