Foam Without Waste: A Dilution Ratio for Shampoo in a Foaming Dispenser That Preserves Cleaning Power

This study examines a practical question in everyday hygiene by explicit arithmetic from stated assumptions. Neat use applied surfactant at 15% at the point of contact but averaged 4.1% over the head after spreading losses. Dilution to the threshold occurred at a ratio of 1:11.5, and the recommended working ratio of 1:4 delivered 3.0% at the hair, a margin of 150% above threshold. Annual product consumption fell from 1248 mL neat to 374 mL diluted, saving USD 10.48 per person per year at the stated price, while one diluted wash at the working ratio outperformed, on spread coverage, the first of the customary two neat washes, which used 16 mL in total. The proposed arrangement is as follows. The deliverable is a fill rule for the dispenser, stated as product and water measures to marked lines, with the margin above threshold chosen to cover variation in hair length, oiliness and water hardness without returning to neat use. The foam format itself does part of the work, since foam cannot pool in one spot the way a poured ribbon does. All results are derived from the accompanying simulation script, in which every assumption appears as a named, replaceable value. SIMULATED, NOT MEASURED.