JOURNAL OF THE SOCIETY OF COSMETIC CHEM1STS .: • . ß .. Figure 1. Expanded silica particles as supplied to dentifrice manufacturers ( x 200 000). Sub-particles are cl•rly s•n closely aggregated to form particles of cloudy struct•e. Figure 2. Extraction replica of Paste B ( x 7000). Note the granular appear- ances of some particles, and the cloudy appearance of others. The structure of particles can be controlled by the size of sub-particles and the degree of expansion. The mass of larger particles is sufficient to render them electron opaque and consequently homogenously black in appearance. Facittg page 482
JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure 3. Extraction replica of British Reference paste ( x 7000). Note the replicated crystal tips (p), and the particle shape typified by many conical protuberances. Figure 4. Extraction replica of British Reference paste ( x 42 000). Note the ease of penetration of electrons near the bases of conical protuberances.
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