Working pH
The working pH is the pH of the cleaning solution as it is applied, already diluted in water, and not that of the concentrated product.
pH measures the acidity or alkalinity of an aqueous solution on a scale from 0 to 14: 7 is neutral, below is acid and above, alkaline. It is a logarithmic scale, so each unit represents a hydrogen ion concentration ten times higher or lower. When a product is diluted, its pH moves towards 7, but not proportionally: it depends on the strength of the acids or bases it contains and on its buffering capacity. The hardness and alkalinity of the water, and the soil that gradually dissolves, also change the pH of the solution during use.
The working pH determines which soil is removed and which materials the solution is compatible with. Alkaline solutions act on fats and proteins; acid solutions, on limescale and mineral deposits; neutral solutions, on light soiling on delicate surfaces. Disinfectants and enzymes have their own pH range of activity, and mixing products can shift it or release dangerous gases. It is checked with indicator strips or a pH meter.
That is why technical data sheets state how the pH was measured: «pH (1 %)» corresponds to a 1 % dilution and «pH» on its own, to the product as supplied. Examples of Instaquim products for foam cleaning in the food industry, according to their technical data sheet:
- Gras Foam: pH (1 %) 12.2; used at 2 to 6 % for heavily greased surfaces.
- Neutro Foam: pH 5.5; used at 1 to 5 % for all types of surfaces.
- Acid Foam: pH (1 %) 2.2; used at 2 to 5 % for limescale deposits.