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Hi.
I made a recipe of 15% ascorbic acid and 0.5% Ferulic and 1% L-Glutathione Reduced (Extrasol) with 30% Glycols of Ethoxydiglycol and Propanediol. The final PH is 3.1-3.4 and the preservative is Phenoxyethanol & Ethylhexylglycerin.
At first, it is quite difficult to dissolve Extrasol completely without high shear.
After a few weeks, it started to have some clear crystals in the bottom and the crystals became bigger and bigger over time.
Why is it happening?
How to dissolve Extrasol well? If I raise PH to 4.5, it dissolves very well and fast.
Thank you.

Hi,

The solubility of L-Glutathione Reduced (Extrasol) in water depends on the pH and temperature of the solution.

There are 2 limitation in your formulation.

1. The amount of water is not enough for proper dilution of L-Glutathione Reduced (Extrasol)

2. The pH of solution is too low

You may either replace some of glycol content by water OR raising the pH of your formulation.

An obvious drawback of high pH is the decrease of ascorbic acid's stability so we suggest that you increase the water content.

Hi.
I tried some method but it is still not very effective.
I made a simple batch:
Water q.s
Ethoxydiglycol 20%
L-Glutathione: 1%

It doesnt dissolve completely. The water content should be enough for dissolving Extrasol, according to your file.
PH is 7.0
What is wrong?

Hi,

This is mainly caused by the insolubility of Glutathione in Ethoxydiglycol.

Remove Ethoxydiglycol or reduce it down to a minimal amount and you shouldn't see any precipitants.