Powder and scent booster
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What they are
A laundry powder and a scent booster. Both dry, both scooped or poured dry into a machine, both bought in a quantity that lasts a season.
The archetype
Bulk, 1000 to 8000 mL, wide mouth, HDPE or PP with PET as an alternative, with a plain closure or a spout. Wide, because the user puts a scoop into it.
The alkali latitude
Ten percent free or chemically unneutralized hydroxide before a child resistant closure is required, against two percent for a liquid. For a builder-heavy powder that is the difference between a plain lid and a child resistant one.
Caking is the failure that defines the format
Powder plus humidity equals a solid block. The container is part of the defence: a good seal, an opaque wall and enough headspace that the customer can break it up if it starts.
Which argues for a tub rather than a bag
The shelf carries 5 PP round tubs and 4 HDPE round tubs with a handle at this size. A resealable rigid container keeps humidity out far better than a bag that has been opened and rolled shut.
Scent booster is the small, dense one
A booster is used in much smaller doses than a detergent, so the same number of washes fits in a much smaller container. It sits at the bottom of the window rather than the top.
Dust at the fill
Filling a dry product at speed makes dust, and dust on a sealing surface is how a tub that was tested as a good seal becomes a bad one. Wipe the rim before the lid goes on, and build that into the process rather than the instructions.
Weight, not volume
Dry products settle. Fill by weight, declare by weight, and expect the container to look less full by the time it reaches the customer than it did when it left.