The pH-value is a concentration measurement of H3O+ (acidic) and OH- (basic) ions. In neutral water, the pH-value is 7, at this point the concentration of the two ions is equal. The lower the pH-value, the more acidic is the water; the higher the value, the more basic. The conversion is made via the negative decadal logarithm: A pH change of 1 corresponds to a 10 x higher or lower ion concentration. Since the skin has a natural acid protection and has a pH-value of about pH 6, a pH-value between 5 and 7 is considered optimal for textiles. Alkaline textiles (pH value > 8) can irritate the skin just as much as very acidic textiles (pH value < 4).
To determine the pH-value, the acidic and basic ions are extracted from the textile in saline water (A defined amount of salt is added to the water prior the extraction, because conductivity is indispensable for the measurement). After the extraction, the pH-value of the extract is determined. The process can be applied to textiles of all fibres and all shapes, whereby very voluminous fibre types such as cushion fillings or nonwovens can make extraction difficult. Water-repellent finishes can also falsify the measurement.
At CTL® GmbH we determine the pH-value between pH 2 and pH 13. As a rule, these limits are not exceeded or undercut in textiles.