Henna was mixed with lemon juice with lemon juice and applied to the hair at the left, seen above. Henna was mixed with boiling water and applied to the swatch on the right. When the henna was rinsed out, the swatch with the lemon mix was a paler orange, and the swatch mixed with water was a brighter orange. Over several months, the mildly acidic stain shown at left gradually darkened while the water stain gradually faded.
Lawsone in the henna will bind permanently to keratin without boiling1 or mordants2 if mixed with a mildly acidic liquid.3 The acid penetrates the cellulostic material in the powdered leaves, and makes the lawsone available for binding. As long as the mix is hydrogen-rich and mildly acidic4 the hydrogens on the corners of the lawsone molecule will be preserved, so the dye will bind to the keratin of hair in a Michael reaction. Lawsone binds so strongly to keratin that even repeated bleaching will not completely remove the color. Lawsone does not ‘coat’ the hair, it binds into the keratin scales that make up the outside layer of the hair. Once bound into hair, the lawsone molecule will gradually darken, unless something is done to prevent that darkening. Fruit juices with their differing pH, differing kinds of acid, anti-oxidants, pigments and enzymes
slightly change the tone, saturation, and oxidation of lawsone and chrysophanic acid in hair.
Read more: https://www.mehandi.com/v/vspfiles/downloadables/chapt6_henna-and-acidic-mixes.pdf
Links to specific topics in this chapter:
Henna, Cassia, and Mildly Acidic Mixes
Citrus Fruits and Citric Acid
Ancient Sunrise® Amla, Emblica Officinalis
Acids with Anthocyanins and Antioxidants
Ancient Sunrise® Kristalovino and Ancient Sunrise® Malluma Kristalovino
