pH, and what it decides

The most informative single number about a cleaning product, and the one that decides several things at once.

One number, four consequences

What it cleans. Alkaline lifts grease, acidic dissolves scale.

What it damages. Both ends attack something.

Which preservative works. Most have a narrow effective range.

What the label has to say, because the extremes are hazardous substances.

The cleaning consequence

Below 4, descaling and rust removal. Around neutral, gentle general cleaning on delicate surfaces. Above 10, degreasing. Above 12, oven and drain chemistry.

A cleaner in the middle is safe and mild and will not do heavy work, which is the trade a "gentle all-purpose" product is making whether or not it says so.

The safety consequence

An extreme pH is hazardous whatever the ingredient. It burns skin and eyes, and alkaline burns are worse than they feel because the pain is delayed.

It also decides what the bottle is made of, what the closure has to be, and what the cautionary label says.

And it decides what the customer can safely use it on: natural stone, aluminum, grout and finished wood are all damaged at one end or the other.

Measuring and holding it

A meter, calibrated, not strips. Strips are fine for a rough check and useless for a specification.

Measure at a standard temperature, and measure the finished product rather than a dilution unless the dilution is what you sell.

Record a target and a tolerance on the formula sheet, and check every batch against it. pH is a good batch-to-batch indicator you have: if it has moved, something else has too.

And buffer where you can, so the formula holds its pH rather than drifting with a slightly different raw material lot.

References