Shipping it by the case
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Spice ships well by weight and badly by value: the product is light, the packaging is most of the mass, and a single broken jar costs more than the order earned.
Small, light and fragile in the wrong way
A case of spice is not heavy, so freight class is rarely the issue. What is at issue is that glass jars in a box with nothing between them will find each other, and that a case of small items has a lot of internal void.
What a case has to survive
Drops onto a corner, compression from whatever is stacked on it, and vibration for hours. Dividers or a molded insert do more than extra outer board, because the failure mode is jars striking jars rather than the box collapsing.
Seal the case properly and mark it as glass if it is. Neither guarantees careful handling and both improve the odds.
Configuration decides your costs
Case count is not an arbitrary number. It sets your wholesale minimum, your shelf replenishment unit, the pallet pattern if you ever get there, and how much a retailer has to commit to in order to try you.
Twelve is the conventional spice case and it is conventional for a reason: it is a sensible shelf facing and a sensible first order. Six lowers the barrier for a small store and doubles your per-unit packing cost.
Pick it before printing anything that references it, because the case count appears on sell sheets, price lists and purchase orders and changing it later is a documentation exercise.
Direct to consumer is a different problem
One or two jars in a mailer is a different engineering problem from twelve in a case, and it is the one most small producers get wrong first. A single jar needs to be immobilized rather than merely cushioned; a jar that can move will break regardless of how much paper surrounds it.
Work out the postage on a packed sample before setting a shipping price, because at these unit values the carriage is frequently a larger number than the goods.