Under weight packaging

Okell

p00hsticks said:

the_lunatic_is_in_my_head said:

PHK said:

Here's the law on the matter:
https://www.gov.uk/weights-measures-and-packaging-the-law/packaged-goods#:~:text=the contents of the packages,more than twice the TNE

The law applies to the average weight of a batch of a product not to the weight of an individual packet. It's also says that no more than 2.5% of a batch can be more than twice the tolerance. 

So it's quite acceptable in law for part of a batch to be under or over weight. I think this makes sense with natural things like a chicken breast or cuts of meat. Animals aren't uniform and butchers can't exactly cut a specific weight but the law says the average weight has to be given. 

I'm not sure how the 3rd rule is applied as the TNE has n/a for certain weights but it seems to suggest a 400g product shouldn't be out by more than 6% in terms of quantity. 

My reading of it would be that if you weighed a batch of 200 products, your procedures should take steps to ensure that at most 5 of them (2.5%) were more than twice the given tolerance

I don't think your right.

The .gov.uk website doesn't clearly reflect what I think(?) are the current regulations - The Weights and Measures (Packaged Goods) Regulations 2006 (legislation.gov.uk).

Reg 4(c) says that a  packer/importer is not allowed to have ANY packages greater than twice the TNE.

Schedule 3 defines the TNE for different labelled/packaged quantities.

Schedule 2 defines the reference tests that must be used to determine whether or not a partuclar batch complies with both reg 4(a) - ie that average contents of a test sample shall not be less than the nominal quantity - and reg 4(b) - ie that no more than a defined number of items in the test sample have a negative error greater than the TNE referenced in Schedule 3.

Schedule 2 also lays down the sample size appropriate to different batch sizes and the test being used.  AIUI the max. sample size is either 125 or 160 (depending on the test being used) and this sample size relates only to batches exceeding 3200 packages.

Okell

the_lunatic_is_in_my_head said:

PHK said:

Here's the law on the matter:
https://www.gov.uk/weights-measures-and-packaging-the-law/packaged-goods#:~:text=the contents of the packages,more than twice the TNE

The law applies to the average weight of a batch of a product not to the weight of an individual packet. It's also says that no more than 2.5% of a batch can be more than twice the tolerance. 

So it's quite acceptable in law for part of a batch to be under or over weight. I think this makes sense with natural things like a chicken breast or cuts of meat. Animals aren't uniform and butchers can't exactly cut a specific weight but the law says the average weight has to be given. 

... but it seems to suggest a 400g product shouldn't be out by more than 6% in terms of quantity. 

I think that's correct.  The TNE for a 400g package is 3%, so no packages more than 6% underweight are allowed.

the_lunatic_is_in_my_head said:

PHK said:

Here's the law on the matter:
https://www.gov.uk/weights-measures-and-packaging-the-law/packaged-goods#:~:text=the contents of the packages,more than twice the TNE

The law applies to the average weight of a batch of a product not to the weight of an individual packet. It's also says that no more than 2.5% of a batch can be more than twice the tolerance. 

So it's quite acceptable in law for part of a batch to be under or over weight. I think this makes sense with natural things like a chicken breast or cuts of meat. Animals aren't uniform and butchers can't exactly cut a specific weight but the law says the average weight has to be given. 

I'm not sure how the 3rd rule is applied as the TNE has n/a for certain weights ...

The table on the .gov.uk website is lifted straight from Schedule 3 of what I think are the current regulations.  

I'm a bit puzzled as to why the TNE for different nominal quantities alternates between being expressed as (1) a %age of the nominal quantity for some nominal quantity ranges, and (2) grammes or millilitres for other quantity ranges.

Not clear to me why that is necessary...

(I probably ought to know.  I was a trainee TS inspector in a previous life...   )

Ergates

The other thing to do before raising this anywhere is to calibrate your scales (kitchen scales aren't always very accurate).  Easiest way to do this is with a known volume of water.

BiffaBacon

Thanks for all your responses. I'll take note.

BTW, it makes me sound like some sort of freakzoid weighing everything, but it started a few years ago when I noticed supermarkets regularly miscalculate deal offers or miscalculated weights when weighing loose items. (Yes, I need to get out more!)

They're not so bad at it now, other than packaged fresh items. As I said in original post, if it's suppose to be an average weight, I've never found it over!

QrizB

BiffaBacon said:

They're not so bad at it now, other than packaged fresh items. As I said in original post, if it's suppose to be an average weight, I've never found it over!

In my experience, pre-packed broccoli in Tesco is almost always over-weight. You get more broccoli with a 350g pre-pack than you do from buying 350g loose. And that's true for the trimmed weight as well; the extra isn't entirely stalk!

HillStreetBlues

Ergates said:

The other thing to do before raising this anywhere is to calibrate your scales (kitchen scales aren't always very accurate).  Easiest way to do this is with a known volume of water.

You can't calibrate scales that way, the volume of water will change with the temperature.

QrizB

HillStreetBlues said:

Ergates said:

The other thing to do before raising this anywhere is to calibrate your scales (kitchen scales aren't always very accurate).  Easiest way to do this is with a known volume of water.

You can't calibrate scales that way, the volume of water will change with the temperature.

It changes by less than 1% between 0C and 40C. It's likely to be good enough for kitchen scales.

https://www.internetchemistry.com/chemical-data/water-density-table.php

HillStreetBlues

QrizB said:

HillStreetBlues said:

Ergates said:

The other thing to do before raising this anywhere is to calibrate your scales (kitchen scales aren't always very accurate).  Easiest way to do this is with a known volume of water.

You can't calibrate scales that way, the volume of water will change with the temperature.

It changes by less than 1% between 0C and 40C. It's likely to be good enough for kitchen scales.

https://www.internetchemistry.com/chemical-data/water-density-table.php

It still doesn't make it a good way to calibrate something, why use something can vary, never mind the fact you have to accurately measure the water in the first place.

EnPointe

PHK said:

Here's the law on the matter:
https://www.gov.uk/weights-measures-and-packaging-the-law/packaged-goods#:~:text=the contents of the packages,more than twice the TNE

The law applies to the average weight of a batch of a product not to the weight of an individual packet. It's also says that no more than 2.5% of a batch can be more than twice the tolerance. 

So it's quite acceptable in law for part of a batch to be under or over weight. I think this makes sense with natural things like a chicken breast or cuts of meat. Animals aren't uniform and butchers can't exactly cut a specific weight but the law says the average weight has to be given. 

exactly   and why  in the 'traditional' butcher's shop  meat prices are quoted as  £x.xx per  unit of mass  ( traditionally the pound  except for  expensive steak were it;s by the ounce ) but  since we neded the modern era by the kilogram...  so each piece  was weighed and priced  accordingly  

molerat

HillStreetBlues said:

QrizB said:

HillStreetBlues said:

Ergates said:

The other thing to do before raising this anywhere is to calibrate your scales (kitchen scales aren't always very accurate).  Easiest way to do this is with a known volume of water.

You can't calibrate scales that way, the volume of water will change with the temperature.

It changes by less than 1% between 0C and 40C. It's likely to be good enough for kitchen scales.

https://www.internetchemistry.com/chemical-data/water-density-table.php

It still doesn't make it a good way to calibrate something, why use something can vary, never mind the fact you have to accurately measure the water in the first place.

Where are you going to get a known volume of water - a bottle of water is going to be measured to the same tolerances as anything else -  or where are you going to get your jug calibrated ?

All I know is my kitchen scale give the same to the gramme as my local PO