Yesterday I made my exfoliating toner with 2% salicylic acid (pH 3.74).
Later on I checked the toner and to my surprise it has turned into a gel! ?
I change the formula now and then a bit, this time I lowered the amount of pentylene glycol because I also use betaine (trimethylglycine) as solubilizing aid for the SA. I also like to use extracts, which vary from time to time, depending on what I have in stock that can be used in this formulation.
I always use dipotassium glycyrrhizate (0.5%) in this toner and I know this licorice salt can form a gel at a low pH in the presence of inorganic acids.
But I don't use inorganic acids.
Or so I thought?
Could it be that it has reacted with the hibiscus extract (2% Prodhy-Extract Hibiscus (Aqua (and) Propylene Glycol (and) Hibiscus Sabdariffa Flower Extract) that I used this time?
I know hibiscus is quite acidic, but I don't know if it contains inorganic/mineral acids by nature?
The LOI of my toner:
(Aqua, Propanediol, Betaine, Pentylene Glycol, Salicylic Acid, Glycerin, Propylene Glycol (from the extracts), Dipotassium Glycyrrhizate, Sodium Hydroxide, Hibiscus Sabdariffa Flower Extract, Calendula Officinalis Flower Extract, Anthemis Nobilis Flower Extract, Tilia Cordata Flower Extract, Centaurea Cyanus Flower Extract, Chamomilla Recutita (Matricaria) Flower Extract, Hypericum Perforatum Flower Extract, Allantoin, Phenoxyethanol, Ethylhexylglycerin, Dinatrium EDTA.)
Contains Euxyl PE 9010: 0.3% (it might not even be necessary, but just to be on the safe side).