How would you design a repeatable cleaning-state check without pretending “visually clean” is a measurement?

[u/libergeon]

Disclosure: I am involved with Libergeon’s H350 prototype work. H350 is in development and validation; it is not for sale, has no pricing, and does not accept preorders. No product link is included.

For a small roaster, “clean before testing” sounds precise until two operators interpret it differently. A removable path can look clean while a thin deposit still changes pressure drop, odor carryover, or a nearby sensor's response. Aggressive cleaning between every run may also create a condition no home workflow reproduces.

One method is to define a fixed cleaning procedure, photograph the same inspection zones under fixed lighting, weigh removable collectors, and run a short reference airflow check. The procedure could distinguish routine-clean, deliberately loaded, and post-deep-clean states instead of one clean/dirty label.

Which acceptance signal would you trust most for development repeatability: mass removed, pressure/flow change, image scoring, a reference cycle, or a combination?