The following data show the relative differences among treatment types for several categories of performance-improvement testing. Some are based on quantitative performance oriented test results, while some are qualitative, based on panelist evaluations. All of these data, qualitative and quantitative, were designed, conducted, and reported by JCH Consulting, whose princi- pal, Jane Hollenberg, has graciously allowed their use here for the discussion of color treatment.
Editor’s Note: The following test results were part of work I performed some time ago to quantify the effects of surface treatment on pigment per- formance in actual products. Basic methodology, not requiring sophisticated instrumentation, was used, which formulating chemists can duplicate.
Compressibility:This factor is always an issue with pressed powder prod- ucts. The ability of various surface treatments to impact it is shown in Figure 8.1. These data were compiled by surface treating all of the pig- ments and fillers used in a pressed powder foundation with each of various treatment actives and then compacting them into typical pressed powder pans. The pans were dropped from a prescribed height on to a hard surface repeatedly until the cake broke. The higher the numbers of drops a pan could withstand before its cake broke, the better its compressibility. The results demonstrate that the control, made with untreated materials, has the worst compressibility, while the silane treatment has the best.
Hydrophobicity:This attribute plays a role in adhesion to the skin and color fastness. As hydrophobicity increases, so does a product’s ability to withstand the effects of perspiration. Figure 8.2 shows comparison data on several treatments with respect to their hydrophobic nature. The data were gathered by measuring the percentage of methanol required to reduce
k k 144 C O L O R I N G T H E C O S M E T I C W O R L D
8 7 6 5 4 3 2 1 0
Untreated Amino Acid
Perfluro Methicone Metal Soap
Lecithin Titanate Ester
Silane 6.1
4.2 4.5 4.5
3.8 3.0 3.2
2.5
Figure 8.1 Compressibility.
100
80
% Methanol 60
40
20
5 8 10 10
20
30
60
70
90
0 Untreated Polyethylene Amino Acid
Lecithin Titanate Ester
Metal Soap
Methicone Silane Perfluro
Figure 8.2 Hydrophobicity.
the hydrophobicity of a treated titanium dioxide pigment to zero, as evi- denced by complete wetting of the powder when a set amount was added to the liquid. The higher the percentage of methanol required, the more hydrophobic the material. In this data set, the untreated control has the lowest hydrophobicity and the perfluoro treated material has the highest.
Oil Absorption:This property is one that must be managed carefully by the formulator to ensure that all shades within the shade range of a color
k k
Surface Treated Pigments 145
80 71
70 66 Octyl Palmitate
60 52
50 50 47 46 44
41 40
30 20 10
0 Untreated Methicone Amino Acid Perfluoro Titanate Ester
Metal Soap
Lecithin Silane
Figure 8.3 Oil absorption.
cosmetic have the same viscosity, stick hardness, or compressibility. The oil absorption of a pigment is determined by porosity, particle size, and affin- ity for the vehicle (wetting). The reader is referred to Table 6.1 to see the vast differences in oil absorption among the various types of pigments. To simplify this part of the formulating task, it may be desirable to reduce the level of absorption by those pigments that exhibit high oil absorptive pow- ers and to surface treat pigments with compounds having functionality to optimize wetting in a given vehicle. Figure 8.3 shows the effects of vari- ous surface treatments on a single pigment: fine particle size mica with octyl palmitate as the oil. The test method employed was ASTM Method D-281-31, Oil Absorption of Pigments by Spatula Rub-Out, as discussed in Chapter 6. The untreated control has the highest oil absorption, while the silane treated sample has the lowest.
Suspension Viscosity:Figure 8.4 shows the effect of various types of sur- face treatments on the viscosity of a 30% suspension of the same mica and oil combination used for the oil absorption test. With particle composition and size constant, variations in suspension viscosity result from differences in wetting caused by surface group modification due to the various surface treatments. In this case, the perfluoro treated mica suspension actually has a higher viscosity than the untreated control, indicating that the treatment reduces wettability. Of those tested, titanate ester and silane treatments have the lowest viscosity suspensions, showing optimized wetting in octyl palmitate.
k k 146 C O L O R I N G T H E C O S M E T I C W O R L D
18,000 16,000 14,000 12,000 10,000 8,000 6,000 4.000 2,000 0
Titanate Ester Silane Metal Soap Amino Acid Lecithin Methicone Untreated Perfluoro
Figure 8.4 Suspension viscosity.
The remainder of the performance data are qualitative in nature, and will be presented as such, showing how the panelists rated the parameters in increasing order of preference.
Creasing:This is a qualitative ranking of the various treatment types based on their ability to prevent or minimize migration of eye shadow color into the crease between the eyelid and the eye socket. The results in Table 8.1 are listed in descending order by level of performance. The only two treatments to perform better than the untreated control are the perfluoro and the metal soap.
Oil Breakthrough:This property is, as its name suggests, a measure of how quickly sebum can be detected breaking through the film of a finished
Table 8.1 Wear results based on creasing.
Perfluoro Metal soap Untreated Methicone Amino acid Lecithin Silane Titanate ester
k k
Surface Treated Pigments 147
Table 8.2 Wear results based on oil breakthrough.
Treatment type Perfluoro Untreated Methicone Metal soap Amino acid Lecithin Silane Titanate ester
Table 8.3 Wear results based on amount remaining.
Treatment type Metal soap Silane Perfluoro Untreated Titanate ester Methicone Lecithin Amino acid
cosmetic once applied on the skin. The evaluation was performed using a pressed powder eye shadow. The results in Table 8.2 are listed in descend- ing order by level of performance. They show that only the perfluoro treat- ment is perceived by the panelists to be better in this regard.
Wear: This property is determined qualitatively by how much finished product remains on the skin after a set period of time. The results are shown in Table 8.3. Metal soap, silane, and perfluoro treatments can be seen to have increased retention of eye shadow. It should be noted that the silane treatment caused a negative effect: significant color change due to increased oil absorption.
Overall Appearance:This property is a measure of how the finished prod- uct appears after a period of wear, as compared to how it looked when first applied to the skin. The results, shown in Table 8.4, indicate that overall appearance after six hours’ wear is improved over the control by metal soap, perfluoro, and Methicone treatments, despite less product remaining with the latter.
k k 148 C O L O R I N G T H E C O S M E T I C W O R L D
Table 8.4 Wear results based on overall appearance.
Treatment type Metal soap Perfluoro Methicone Untreated Amino acid Lecithin Silane Titanate ester