If you take one thing from this library into your next negotiation, make it this: a price is meaningless until you know what weight it applies to.
The three weights
For a frozen seafood consignment there are at least three different weights in play, and they are not close together.
Gross weight is everything on the scale: product, glaze, inner packaging, carton and sometimes the pallet. It is a logistics figure. It should never be the basis of a price.
Net weight is the product plus its glaze, with packaging excluded. This is what many suppliers mean when they say “net”, and it is where most misunderstandings begin.
Net weight excluding glaze — usually written net of glaze — is the actual quantity of seafood. This is the number your costing depends on.
Why the gap is large
Glaze is a layer of ice applied to frozen product to limit dehydration and oxidation. It is a legitimate and necessary part of frozen seafood production. It is also water, and it is weighed.
At 10 % glaze, a 10 kg carton contains 9 kg of product. At 20 % glaze, the same carton contains 8 kg. Two suppliers quoting the identical price per kilogram, one at 10 % and one at 20 %, are more than 12 % apart on the price of the actual seafood — and nothing in either offer looks wrong.
How to write it
Put the weight basis in the enquiry, not in the reply. Three sentences are enough:
Price to be quoted per kilogram net of glaze. Glaze percentage to be stated and not to exceed [x] %. Net-of-glaze weight to be verified on arrival by [agreed method].
Then make sure the same words appear on the purchase order, the specification sheet, the packing list and the invoice. A weight basis agreed in an email and absent from the documents is not an agreement.
Verification
Net-of-glaze weight is determined by removing the glaze under controlled conditions and reweighing. Agree the method and the sampling plan in advance — how many cartons, drawn from where in the consignment, and by whom. Disputes about weight are rarely disputes about arithmetic; they are disputes about method.
The same principle, other forms
The logic extends beyond glaze:
- Prawns in brine are sold on drained weight, not the weight of the filled pail.
- Fresh fish packed with ice is sold on drained weight without ice.
- Dried products carry a moisture content that decides how much finished food a kilogram becomes.
- Salted products carry a salt content that does the same.
In every case the question is the same: what proportion of the weight I am paying for is the thing I actually want?