18

Under many of my food storage containers of plastic, there are circles with numbers and an arrow in the middle pointing at one of the numbers. What does these symbols mean?

Could it be recycling information? Plastic type? Production date? Serial number? Suitable for a special type of food?

Here is a picture of a food storage container of plastic from IKEA:

Clock-like symbols under plastic container
(click for full size)

Improve this question
1

3 Answers 3

Reset to default
19

This is the date the item was manufactured. The upper dial gives the year, the middle one, the month.

The bottom indicator could be a mold identifier, and in some cases, it might be a shift indicator (although this would typically be a clock going from 1 to 3, 4, or 6 depending on how shifts are allocated rather than the example showing 0 to 5).

See e.g. this manufacturer's datasheet on mold indicators: http://www.plastixs.com/pdfs/datecodeti.pdf

Improve this answer
6
  • 4
    The bottom dial could also be the mold number. Most commonly these "clock" symbols only indicate the mold used to form the part -- quality dept at the factory can then quickly track down which mold may need maintenance if faulty product is noticed. I think you're completely correct that the upper two are date-related, though.
    – Erica
    Jan 15, 2015 at 12:38
  • @Erica - that is a very credible alternative explanation. I am going to update my answer this evening once I've found a good reference for this.
    – James McLeod
    Jan 15, 2015 at 13:06
  • The year and month is correct as defined here cpsc.gov/en/Recalls/2012/…
    – Huangism
    Jan 15, 2015 at 19:07
  • Just saw a video talking about injection molding of plastic : youtube.com/watch?v=RMjtmsr3CqA . They're mentioned right at the end, at about 8:20.
    – Joe
    Nov 24, 2015 at 19:00
  • Oops, the link is dead.
    – Catija
    Jan 2, 2017 at 23:38
2

Top to bottom: Year, Month, Week. See D-M-E injection mold components catalog p157. If a problem turns up, the date markers will allow the investgating team to run down the batch.

Improve this answer
2
  • 2
    If the third one is the week, then why are there six options?
    – Niall
    Jan 11, 2017 at 12:21
  • Local law says a work week is 5 days with two days off or pay overtime. 5 days into most months is 6 weeks.
    – user53594
    Jan 19, 2017 at 22:31
1

At our plastic company, the last dial is the material source identifier. We source the injection molding pellets for HDPE from different manfacturers of comparable quality to keep them hungry and to keep us from having a supply crisis. 1 = company 1's resin, 2 = company 2', etc. This way you can trace a quality issue to the date and material source. sometimes it is a shift and sometimes it is a day of the week, just depends on the company.

Improve this answer

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.