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Water Based Thickeners

• The easiest way to add xanthan gum to the water phase of your formulations is to first disperse the gum into a water-miscible solvent like propanediol, butylene glycol, or glycerin before adding to water.
• Use combinations of thickeners that work by different mechanisms to achieve maximum viscosity using the least amount of material. Examples include combining swellable polymers with soluble polymers, or clays with swellable or soluble polymers.
• Oil-in-water emulsions thickened using swellable polymers like carbomers and acrylate copolymers can sometimes be difficult to pick up and spread on skin due to their salt sensitivity. Adding .1-.2% xanthan gum can significantly improve pickup and product spreadability.
• Adding swellable- and soluble-polymers to the oil phase of oil-in-water emulsions prior to emulsification can frequently improve the quality of the emulsion. The technique works well for neutralized swellable-polymer powders or dispersions and soluble-polymers like xanthan gum.
• Use surface-treated easy-to-disperse grades of powdered carbomers and acrylate copolymers for easier incorporation into water.
• The best thickener to formulate high alcohol (60-90%) sanitizer formulations is acrylates/C10-30 alkyl acrylate crosspolymer neutralized using triisopropanolamine or tetrahydroxypropyl ethylenediamine.
• The most efficient salt-stable all-natural-based thickening system is a mixture of konjac glucomannan (amorphophallus konjac root extract) and xanthan gum.

Oil-in-water emulsions

• When formulating thin, stable, sprayable oil-in-water emulsions, use thickener combinations that have a high yield value or resting viscosity. Examples include magnesium aluminum silicate, sodium magnesium fluorosilicate or microcrystalline cellulose combined with xanthan gum or carboxymethyl cellulose.
• Always add salts after emulsification to lamellar gel network-based formulations for maximum viscosity and stability. Ideally below the phase transition temperature (<45C).
• Adding low levels of soluble- or swellable-polymers to lamellar gel network-based formulations can reduce the graininess commonly seen in freeze/thaw stability samples.
• Using a 60% or 90% mono glyceryl stearate in oil-in-water emulsions will normally give you a better emulsion and skin feel than using a conventional 35-40% mono glyceryl stearate.
• A natural based oil-in-water lamellar gel network-based emulsion with good long-term stability is stearyl alcohol 2%, glyceryl stearate (60% mono) 2%, and triglyceryl stearate 1%.

Water-in-oil emulsions

• Adding zinc sulfate can help stabilize water-in-oil emulsions and significantly reduce the preservative level in the formulation. Chelating agents should not be used in this application. Currently, most water-in-oil emulsions use sodium chloride or magnesium sulfate as stabilizers.
• Adding low levels of soluble- or water-swellable-polymers to the water phase of water-in-oil emulsions can significantly improve their freeze/thaw stability.
• Over shearing water-in-oil emulsions can cause a viscosity decrease over time.

Solubilizing oils into water

• When solubilizing fragrances into water start by using 5 parts of active solubilizer for every part of fragrance. If successful, reduce the solubilizer to the point of failure. This will establish the working range of the solubilizer.
• Polar oils, like fragrances, are significantly easier to solubilize than most cosmetic emollients. It can take as much as 15-20 parts of solubilizer for each part oil compared to 3-5 parts for most fragrances.
• Good natural based solubilizers include polyglyceryl 10 oleate and sorbitan oleate decylglucoside crosspolymer.

Emollients

Use emollients in formulations that have good skin feel and clinically proven skin effects. Examples of natural emollients include squalane, and jojoba oil. Others to consider include isostearyl isostearate, C12/13 lactate, myristyl lactate, and isosorbide dicaprylate.

For more information, please continue to Part Two

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