Many nat­u­rals report that their hair feels and even behaves dif­fer­ent­ly when they live, move or vaca­tion in an area with hard water. I now final­ly have sci­en­tific answers as to what could be hap­pen­ing!

1. The cuti­cle sur­face is the first point of call for both soft and hard water

Both soft and hard water con­tain met­al salts includ­ing notably cal­ci­um and mag­ne­sium. Hair seems to have a pref­er­ence for cal­ci­um ions and when hair is placed in hard water, cal­ci­um deposits at the cuti­cle edges and a lit­tle bit may trav­el inside the cuti­cle lay­ers but not real­ly into the cor­tex (BBA, pp 1–5, 2003).

water hardness

2. It may be more about pH than water hard­ness

Inter­est­ing­ly exper­i­ments have shown that for unbleached nat­u­ral hair, there is lit­tle dif­fer­ence in the cal­ci­um deposits whether soft, hard or very hard water is used (J Cos­met Sci, pp 383–391, 2011). How­ev­er, if the pH of the water is changed e.g com­par­ing hard water at pH 7 to hard water at pH 8, then there is an increase in the depo­si­tion of cal­ci­um. Nat­u­ral­ly hard water does tend to have a high­er pH so it stands to rea­son that a poten­tial fix for hard water may be adjust­ing its pH (e.g with lemon juice or apple cider vine­gar).

3. Hard water makes nat­u­ral hair a lit­tle more rigid

The effect of hard water does change if hair is chem­i­cal­ly bleached or not. For unbleached nat­u­ral hair, hard water use results in hair becom­ing a lit­tle more rigid com­pared to using soft water (tech­ni­cal ter­mi­nol­o­gy is an increase in Young’s Mod­u­lus). The impli­ca­tion for hair is that when it is wet with hard water, it is resis­tant to exten­sion and will there­fore require a lit­tle more stress (5% more) to break (Int J Cos­met Sci, pp 477–482, 2011). If your hair is straight to wavy, there are some advan­tages to this as you can use less force to comb your hair, how­ev­er for curlier hair, this means a loss in flex­i­bil­i­ty and there­fore you need to be care­ful when wet detan­gling.

4. Hard water can help your twist out last longer in humid­i­ty

Humid­i­ty can wreak hav­oc on some hair styles such as twist outs or curl/rod sets. A sur­pris­ing advan­tage here for hard water is that the extra deposits of met­al salts on the sur­face of hard water can actu­al­ly give nat­u­ral hair some humid­i­ty resis­tance allow­ing a set style to last just a lit­tle bit longer. This is thought to be pos­si­bly because cal­ci­um and mag­ne­sium may occu­py spots on the hair where water vapour may want to bind and there­fore slow down water uptake (Int J Cos­met Sci, pp 477–482, 2011). The increased resis­tance to humid­i­ty lasts about 2 hours show­ing that mois­ture uptake in humid­i­ty does hap­pen, just slow­er.


Is hard water promi­nent in your area? How does it affect you?

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1 Comment on "How Hard Water Scientifically Affects Natural Hair"

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Maja T.

Hi, I agree, hard water is real­ly bad for our hair. I just shared a sim­i­lar post on my blog: Please take a look and let me know your opin­ion.