Week 4 · Experiment Diary

Week 4: A 28-day Central hard-water fade experiment

NEO·2026-04-21

Central hard water hair colour fade 28-day experiment

I ran a small experiment this week: same formula (Wella 7/77 + 6/3, 6% developer, 30-minute processing) on four clients living in Central, Sheung Wan, Sai Ying Pun and Taikoo Shing. After 28 days they returned for a fade comparison — and the results made me rethink the 'water quality' conversation.

Experiment design

Four clients with comparable hair condition, length and density. All freshly coloured, no other treatments. Identical home regimen: Milbon Aujua colour-safe shampoo, weekly Olaplex No.3, no blow-drying with hot air. Only variables: home district water and wash frequency. After 28 days I measured ΔE at six points using an X-Rite Ci64 colorimeter.

The result: district isn't the biggest variable

Central averaged ΔE 6.2, Sheung Wan 6.8, Sai Ying Pun 5.9, Taikoo Shing 5.4 — a spread under 1.5, smaller than expected. But look at wash frequency: the Taikoo client washed 3 times a week (lowest) and had the lowest ΔE; the Central client washed daily but kept water below 38°C and her ΔE wasn't dramatically worse. The Sheung Wan client showed the worst fade — she used 42°C hot water daily.

Insight: wash frequency and temperature outweigh 'water hardness'

Hong Kong Island sits at 80-130 mg/L water hardness — not extreme (compared with New York 60 mg/L or London 270 mg/L). The real colour killer is daily washing + hot water (>40°C) + alkaline shampoo. If you wash every other day with sub-38°C water and a mildly acidic colour-safe shampoo, district barely matters.

Three home-care SOPs I give clients

(1) Keep shampoo water below 38°C (test on your inner wrist) — hot water opens the cuticle and bleeds pigment; (2) Don't wash daily in the first week — let the pigment set for 7-10 days; (3) Choose a colour-safe shampoo at pH 4.5-5.5 (Milbon Aujua, Olaplex No.4); alkaline shampoos double the fade rate.

If you're curious how your home routine is affecting your colour, tell me your wash frequency, water temperature and current shampoo at your next booking — I'll adjust the formula buffer to extend your fade cycle by 30-50%.