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The following instructions are given for a preparation and I am wondering what it means to "shear an emulsion"?

The water phase components and the oil phase components are each mixed in separate containers and filtered and the refractive index of each is measured. The refractive index of the water phase is adjusted to match the refractive index of the oil phase to within 0.0004 by addition of water or propylene glycol as required. The water phase is then slowly added to the oil phase at about 18.degree. C. with sufficient mixing to form a clear emulsion with minimum aeration. This emulsion is then sheared to form a clear gel with a viscosity of about 130,000 to 160,000 cP.

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    $\begingroup$ Check what is meant by shear forces in fluid mechanics. Hint: also see shear thickening and shear thinning. $\endgroup$
    – ACR
    Commented May 20, 2021 at 5:04
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    $\begingroup$ While fluid mechanics is part of curricula in chemical engineering, note that engineering.se may offer a more receptive audience for this question. See this tag as an example. $\endgroup$
    – Buttonwood
    Commented May 20, 2021 at 17:17
  • $\begingroup$ Search for "shear mixer" and you'll get a good idea eg en.wikipedia.org/wiki/High-shear_mixer $\endgroup$
    – Buck Thorn
    Commented May 21, 2021 at 8:16
  • $\begingroup$ You may also want to ask "why shear mix an emulsion?" Look into the Wikipedia article linked above. $\endgroup$
    – Buck Thorn
    Commented May 21, 2021 at 8:23
  • $\begingroup$ An emulsion is made of small droplets in suspension in another liquid. Usually it is not stable. After some time, the two phases get separated. But if the mixture has been sheared, the emulsion is stable like milk and will not get separated. $\endgroup$
    – Maurice
    Commented May 21, 2021 at 9:08

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