I have started working with gellan gum thickened with sodium chloride as a gelling agent because it has a very attractive clarity similar to carbomer.
However, I noticed that solid crystals of kosher salt cause agglomerates to form—the local concentration near the crystals is high enough to gel as it dissolves, before it can disperse.
I'm thinking incorporating salt gradually with a dropper of known concentration will make it possible to do gradual viscosity adjustment in the lab, rather than having to do a "salt curve" of sorts with gellan gum alone.
What minimum percentage of sodium chloride in distilled water would be self-preserving without other additives? Are there any hazards to watch out for, such as the growth of salt-tolerant extremophiles? Is this a common practice, or am I doing something strange?
Additionally, is food-grade kosher salt generally fine for cosmetic formulation? What is the likely composition of the remaining 0.17%? Potassium Chloride?
I've currently got a 35% kosher salt solution (26.9g salt, 50g water) on
my magnetic stirrer hot plate. This is theoretically below the
solubility limit of sodium chloride in water at 0°C, but is not dissolving adequately.