Creams and ointments for topical use on the skin require a combination of physical properties which impart the desired feel when applied. The cream needs to be firm enough to hold its shape when taken from the container, but soft enough to readily spread across the surface of the skin during application. The optimum physical characteristics are provided by an intimate mixture of a solid and liquid phase. In the case of a petroleum jelly this is a combination of paraffin and microcrystalline waxes with a low viscosity oil, which being of similar chemistry are relatively easily combined. For creams the solid phase is usually a vegetable derived wax, with water as the liquid fraction, an emulsion. As ‘oil and water don’t mix’ the challenge becomes how to combine the two very different components together into a lasting, intimate mixture. The solution is to use surfactants, compounds specifically designed to bridge the divide between non-polar oils and the highly polar water. The chemistry of surfactants is very diverse with many options being available to provide the hydrophilic, water loving part of the molecule. Waxes which have been manufactured with the surfactant already incorporated, are known as emulsifying waxes and mixing these with water at the correct temperature is a fast and efficient way of preparing a base cream which can then be augmented with active pharmaceuticals, or fragrance and colour, depending on the intended use.
The choice of surfactant and therefore emulsifying wax is dependent on the other components in the blend and the intended characteristics of the finished cream in use. At Kerax, we manufacture a range of emulsifying waxes using both polar and non-polar surfactants. Our brand new, all stainless steel, dedicated manufacturing facility produces emulsifying waxes which conform to the British, European and United States pharmacopoeias. In addition to the standardised products specified in these pharmacopoeias, we recognise that customers may have developed their own formulations , which we are happy to manufacture as part of our bespoke production service.
For a sample of our established range or further information on these products, please contact Clare or Adrian on 01257 237350. Alternatively visit our website www.kerax.co.uk or come and see us on stand 220 at Making Cosmetics, 24th-25th March at the Ricoh Arena, Coventry.