LIFESTYLE COSMETICS


and agglomeration that amplify the variation in colour properties. These pigments cannot be simply stirred


into the desired product, they must be fully dispersed in a vehicle to get as close as possible to primary particle size to see the full development of colour. Dispersion is the process of wetting,


separating and distributing pigment particles in a medium. Dispersion requires intense energy input through high sheering in liquids or pulverization in powders. A particle size < 10 µm is necessary for optimum colour development. Fineness of grind can be easily measured with an instrument called a Hegman Gauge. One note of caution, pigments can be over- milled resulting in lower colour development. Another important factor in pigment


dispersion is the oil absorption capacity of individual pigments. Based on both chemical structure and the type and amount of substrate present in pigments, they will exhibit a wide range of oil absorptive powers. For this reason, the best pigment-to-oil


ratio for dispersion can vary and it is easiest to work with single pigment dispersions. This property is significant in the formulation of lipsticks as the oil absorption of a pigment has a major impact on the hardness of the stick. Oil absorption also impacts the rheology


of an emulsion system and is an important factor in controlling the consistency across a line of colours in a lipstick range or liquid foundations.


Pearlescent effect pigments Pearlescent effect pigments are composed of thin, translucent platelets of materials like mica or synthetic mica (INCI: Synthetic Fluorphlogopite) coated with extremely thin layers of titanium dioxide or other absorption pigments. Smaller platelets give a satin-like


appearance, while larger sizes provide sparkle and glitter. Guanine is a naturally-derived pearlescent material obtained from fish scales but its use in cosmetics today is virtually nonexistent. Pearls can be described in terms of mass


tone (absorption colour) and interference colour. When visible light encounters an object like a particle of mica it can be reflected, refracted or transmitted. Coating mica and other substrates with thin, precise layers of titanium dioxide allows the wavelength of the reflected light to be tuned to produce a specific interference colour. The overall mass tone of the mica is


white, but with a change in viewing angle the interference colour is visible. The interference colour depends on the thickness of the titanium dioxide layer; varying from silver through gold, red, violet, blue and green. Iron oxide can also be utilized to produce metallic bronze, copper and russet red pigments. Deposition of other cosmetic colourants on


top of interference pigments can create even more interesting effects. If the interference colour of the titanated mica and the absorption colour of the deposited pigments


www.personalcaremagazine.com


are the same, the result will be a brilliant, intense colour effect. An example would be the use of iron blue on an interference blue pigment. If the colour of the deposited pigments


is close to the complementary colour of the interference colours, the result is a dramatic, two-tone effect. An example would be carmine with an interference blue pigment. The stability and compatibility issues


inherent to the absorption colour used will persist. In the previous example, a pearlescent pigment created with carmine should not be used in acidic pH or exposed to temperatures above 60°C. There are hundreds of pearlescent


pigments available in various particle sizes to choose from allowing the formulator to create a dizzying number of visual effects. Smaller platelets give a satin-like appearance while larger sizes provide sparkle and glitter. It is important to note that in the United


States, natural mica when used a colourant is restricted to a maximum particle size of approximately 150 microns in cosmetic applications. The iridescence and sparkle created


by pearlescent pigments is dependent on the ability of these particles to reflect light. Opaque formulations, especially those containing conventional pigments, can diminish and obscure the pearlescent effect. Compromise may be necessary but,


whenever possible, translucent ingredients should be utilized. Clear gels are the most


suitable base. When working with powders, it is advisable to use the most translucent fillers available. When blending two or more pearlescent


pigments, it is not advisable to blend multiple interference colours. Interference colour is produced by reflected light and, as a result of additive colour mixing, the combined effect will be white or nearly white and a waste of these costly raw materials. Instead, it is recommended to combine pigments based on the same reflectance colour. In addition to adding iridescence and


sparkle to makeup, smaller particle size effect pigments (<20 microns) can add natural lustre to face and body moisturizers that translates into a radiant appearance on the skin. These particles may also be well suited for use in facial makeup to replace some of the titanium dioxide pigments, which can result in a chalky appearance on darker skin tones. Effect pigments should be added slowly with moderate agitation. Unlike conventional pigments, these additives should not be milled or exposed to high sheer as harsh milling or grinding that can fracture the fragile platelets and damage reflective coatings. Effect pigments must be suspended


in personal care products using rheology modifiers that provide yield value as viscosity alone is not enough to prevent the particles from settling. Examples of ingredients that can provide sufficient yield value include hydroxyethyl cellulose, xanthan gum, carbomer, and other acrylate-based polymers.


25


PC January 2024 PERSONAL CARE


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80