The colouring agents used in the development and manufacture of decorative cosmetics are vital for them to perform their primary function, colouring the skin of the user. Many of the colours used in these products are not used elsewhere in the cosmetics and toiletries field although they are often derivatives of those colours. Some of the top beauty cosmetology colleges in Nashik have dedicated labs for skill-based training to help students understand the concept of colour matching in cosmetics.
The chemistry of the colours used in decorative cosmetics has a large bearing on the type of products in which they are used. Some are not suitable for aqueous media but are widely used in anhydrous systems such as lipsticks and powder products. However, these two largely anhydrous systems are very different from each other. It was decided therefore that the properties of the colours themselves should be considered separately from the formulation of the products. The formulator must check carefully the regulations for the markets for which the products are being developed to ensure that the materials they are using are legal in those markets. Colours are heavily regulated in all areas of the world, and unfortunately the regulations vary from country, or regional area, to country. Specifications for the individual colours may be needed in some places and also batch certification may be required.
Dye
A dye is defined as a colourant which is soluble in a solvent or range of solvents (this includes water). For obvious reasons, dyes themselves are rarely used in decorative cosmetics, because the beautifying effect required is temporary, and stain (‘dye’) on the skin is not needed; but derivatives of the most common dyes are widely used in toiletries. There is however one area where dyes are used. This is in some lipsticks where a claim of ‘long-lasting’ is required and a particular group of them is used called the ‘Eosin’ dyes.
Natural Colours
This group of colours have come to the forefront of consumer awareness recently, mostly because of their increasing use in food products. They are fully permitted for use in cosmetics provided that the materials used meet the required purity. They are not particularly stable, however, especially with regard to heat, light and pH. Only one natural colour, or rather its aluminium lake, is widely used and this is carmine. Carmine has a long history of use in the food industry. It is obtained from the ‘Coccus cacti’ insect (a type of beetle), by aqueous alkaline extraction. The pigment is achieved by forming the aluminium lake of carminic acid. Carmine provides a bright strawberry red shade. Chemically it is very stable and is unaffected by oxygen, light, sulphur dioxide, heat and water. Carmine is one of the few organic colours permitted for use around the eye area in the USA. Its major disadvantage however is its price, several hundred pounds per kilo.
Pigments
Pigments can be defined as coloured or white chemical compounds insoluble in the liquids in which they are used. Chemically they can be divided into two main groups: the very bright, organic pigments and the relatively dull inorganic pigments.
Colour Matching
It is not advisable to add large quantities of pigment to any type of finished formulation to correct the colour as this will unbalance the formulation, possibly leading to separation or thickening over time if it is an emulsion, or a heavier, dry draggy effect of a lip product. Neat pigment is very difficult to disperse once the formulation has been completed.
Lip Products
With lip products additional pigment pastes can be added, but the total dry pigment level should be carefully controlled within well-defined limits. If colour matching within these limits is not possible, extra base ingredients must also be added.
Powdered Products
Colour adjustment in powder products such as eye shadows and face powders is usually accomplished by milling the additional required pigments into a small amount of the finished product and then blending this into the bulk, after ensuring full dispersion has been obtained.
Foundation Make-up
When colour matching emulsion products such as foundation make-up a very small amount of additional pigments is added to a small amount of base removed from the batch and the pigments dispersed in this using high shear mixing. Once homogeneous this is returned to the bulk and stirred with a paddle until the batch is homogeneous again. If a lot of colour corrections are required, or a number of shades of the same formulation are being produced at the same time, the preferred way is to produce separately, prior to production of the marketed shades, a white, black, yellow and red foundation make-up. In these all the pigments in the base formulation are either Titanium Dioxide (for white), Black, Yellow or Red Iron Oxides. When colour matching of the final shade is carried out small aliquots of the appropriate primary coloured base (PCB) can be added as required. In this way the balance and percentage ratio of the product is not disturbed so no long-term stability problems are likely to arise.
Comparison with standard
Whichever way the adjustments are made it is important that the colour of the batch is compared to a previously approved standard. For foundation make-up the comparison is best done on the skin, the forearm being the preferred site. Two strips of the standard are applied, one in line with the base of the thumb, the other higher up the arm on the inside. Two further strips of the production batch are then also applied, one higher up the arm in line with the base of the thumb, the other near the wrist under the second strip of standard. The products are then allowed to dry fully before being compared for colour. By applying the strips in this way on the forearm, any skin tone variation can be cancelled out and a true comparison of the colour achieved. Other products can be compared on the back of the hand or by using the pale skin at the base of the thumb on the palm using the same four-grid pattern.
Conclusion
To summarise, the selection and application of colouring agents in colour cosmetics are important for accomplishing the desired exquisite effects while complying with the regulatory requirements. The use of dyes, natural colours and pigments each comes with particular advantages and challenges, affecting the formulation and stability of products such as lipsticks, powders and foundation make-up. Pursuing a B.Sc in Beauty Cosmetology can help you better understand the concepts of colour matching in cosmetics. Appropriate colour matching techniques are crucial to maintain consistency and ensure product quality without compromising formulation credibility. Given the severe global regulations, formulators must carefully select and certify their colourants to meet market standards, ensuring both safety and efficacy in cosmetic applications.