Elements influencing the assessment of the electrolytes effect on the extension of a drop of shampoo

The method of extension of a drop was applied to evaluate the effect of electrolyte concentration (sodium chloride and ammonium chloride) on the viscosity of a conditioning shampoo. The method showed to be satisfactory employing squared glass plaques of 15 cm and 3 mm thickness. The precision of the method showed to be higher as the exposition time and the weight of the sample increased. The variability of the method allowed to attain C.I._95%<1%. The extension of the drop changes as a function of the sample weight in a cubic relationship passing through the origin although in the studied experimental interval a linear regression is sufficient. An increase in the studied electrolyte concentrations increases the viscosity up to a limit, making possible the manipulation of the shampoo's viscosity.