What to check before filling
Updated
The last point at which a bad batch costs bottles rather than customers.
Five checks, ten minutes
Everything here is quick, cheap and catches the failures that otherwise arrive as complaints months later.
Do them on the bulk, after standing, before a single bottle is filled.
The five
pH, on a calibrated meter, at a recorded temperature. A informative number, and the one that reveals a raw material problem.
Appearance. Clarity or the correct color, no separation, no sediment, no undissolved material at the bottom of the vessel.
Viscosity, by whatever consistent method you use, after the batch has stood.
Odor. Correct and at the expected strength. A weak or off smell is a raw material or a process signal.
Weight. The batch should weigh what the formula says. A discrepancy means something was missed or double-added, and it is the check that catches the expensive mistake.
Against what
A written specification with a target and a tolerance for each, and a retained sample from an approved batch to compare appearance and odor against.
Not against memory, and not against the previous batch, which is how a specification drifts one step at a time.
What to do with a fail
Do not fill. That is the whole point of the check.
Diagnose before correcting: a low pH and a low viscosity together is a different problem from either alone.
Record the deviation and what was done, because the pattern across batches is what identifies a drifting raw material.
And where a batch cannot be brought into specification, dispose of it rather than filling it as a second. A cleaning product with something wrong in it is not a discount opportunity.