Slack fill

A container the consumer cannot see into

On this page11

The condition So visibility is the gate Our shelf is mostly in that category Natural polyethylene is the interesting case Which is a judgment this property does not make The seven clear ones are a different proposition And clear is a real option on this shelf White is the default for a reason Light protection matters for fats Which is itself one of the six reasons References

32 of 39 are opaque or translucent. Which is the ordinary condition here.

The condition

A container that does not allow the consumer to fully view its contents shall be considered to be filled as to be misleading if it contains nonfunctional slack-fill.

So visibility is the gate

The test in paragraph (a) is attached to containers a consumer cannot see into, because those are the ones where empty space is concealed.

Our shelf is mostly in that category

22 white, 8 natural, 1 blue and 1 black against 7 clear. So 32 of 39 do not allow the contents to be fully viewed.

Natural polyethylene is the interesting case

8 containers. It is translucent rather than opaque, so a level can be guessed at and the contents cannot be fully viewed.

Which is a judgment this property does not make

Whether a translucent container allows contents to be fully viewed is a question about a particular container and we publish a color, not a transmission figure.

The seven clear ones are a different proposition

A clear container shows its own fill level, which is the reason the paragraph treats it differently. 7 of 39, all PET.

And clear is a real option on this shelf

2 PET wide mouth containers and a PET single wall canister among them. For a treat sold on appearance that is a deliberate choice.

White is the default for a reason

22 of 39. It is cheap, it blocks light, and it takes a label well, which are the three things a pet food container is usually bought on.

Light protection matters for fats

A freeze dried raw product or a fatty treat oxidizes in light, so the opaque majority is serving a real purpose rather than hiding anything.

Which is itself one of the six reasons

Protection of the contents is reason (1), and it is the reason most often available for a container that is opaque by design.

References

The Davis Pack Supply catalog, measured 19 October 2026. Of the 39 containers in this group, 22 are white, 8 natural, 7 clear, 1 blue and 1 black. So 32 of 39 do not allow a consumer to fully view the contents, which is the condition 21 CFR 100.100(a) attaches its slack-fill test to.

21 CFR 100.100, "Misleading containers": "A food shall be deemed to be misbranded if its container is so made, formed, or filled as to be misleading." Paragraph (a) continues: "A container that does not allow the consumer to fully view its contents shall be considered to be filled as to be misleading if it contains nonfunctional slack-fill. Slack-fill is the difference between the actual capacity of a container and the volume of product contained therein. Nonfunctional slack-fill is the empty space in a package that is filled to less than its capacity for reasons other than:" law.cornell.edu

21 CFR 100.100(a), the six functional reasons, verbatim: "(1) Protection of the contents of the package; (2) The requirements of the machines used for enclosing the contents in such package; (3) Unavoidable product settling during shipping and handling; (4) The need for the package to perform a specific function (e.g., where packaging plays a role in the preparation or consumption of a food); (5) The fact that the product consists of a food packaged in a reusable container where the container is part of the presentation of the food and has value which is both significant in proportion to the value of the product and independent of its function to hold the food; (6) Inability to increase level of fill or to further reduce the size of the package (e.g., where some minimum package size is necessary to accommodate required food labeling)". law.cornell.edu

Written from 21 CFR 100.100 and from the catalog as it stood on 19 October 2026. That section concerns misleading containers and is not a pet food labeling guide: the guaranteed analysis, nutritional adequacy statement, feeding directions and ingredient definitions that govern a pet food label come from state feed laws and the AAFCO model regulations, which are not federal and are not described here. Our capacity field is the actual capacity of the container, which is one of the two terms in the regulation's own definition of slack-fill; the other is a property of your product.