Brookfield AMETEK

Cold Cream

Laboratory Viscometer Application Data Sheet

Personal Care Product (Two Methods)

USE: Cold cream is used (1) to remove facial cosmetics or "make-up", and (2) as a skin cleanser, for example.

Method #1

Test Equipment:

  • Spring Torque Range: RV or HA
  • Spindle: T-F
  • Accessory: Helipath Stand
  • Speed, rpm: 5

The test is run at room temperature.

Different producers use equipment ranging from the Brookfield RVT Dial Reading Viscometer to Brookfield Digital Viscometers or Rheometers. They typically use their own, proprietary choice of T-bar spindle and speed as well. Several readings are made as the spindle travels down [and back up] through the sample. The data are taken at regular intervals such as 30 seconds, for example, and an average value calculated for a QC/QA measure. However, automated data acquisition may be performed with the Brookfield DV-II+ Pro Viscometer and Rheocalc software, for example.

We tested two commercial cold creams: Cream 2 was tested using the RVDV-II+ Pro, while Cream 1 was subsequently tested with the HADV-II+ Pro Viscometer. The HA spring torque range is twice that of the RV; in this case, it allowed on-scale measurements of the more viscous Cream 1, while using the same spindle and speed as that of Cream 2. Typical automated-test data, comparing two different products, are shown below:

The above graph was custom-sized, using the new "Custom" window feature available in Rheocalc32 Version 3.0.

Method #2

Test Equipment:

  • Spring Torque Range: 5xHB
  • Spindle: V-73, immersed to the secondary mark
  • Accessory: (none)
  • Speed, rpm: 1

The test is run at room temperature.

Yield testing with vane spindles is relatively new in QC applications. This test may be considered somewhat more sophisticated than the standard Helipath procedure described above in Method #1. Automated data acquisition was performed in this work with the Brookfield YR-1 Rheometer, using EZ-Yield™ software. Typical data from a comparison of two different products, Product 1 and Product 2, are shown below:

The difference between the materials is significant. Cold cream Product 1 has a higher peak value than that of Product 2. This higher peak corresponds to a greater yield stress. The yield stress is the stress at which a solid material's structure breaks down so that it flows. The initial slope or modulus of the Stress-versus-Apparent Strain curve (shown circled) is greater for Product 1 than for Product 2. This indicates that Product 1 initially is stiffer than the other product. These data reflect Product 1's significantly firmer texture. (The data at the lowest strains have some artifact caused by mechanical "settling" as the spindle and drive system engage with each sample. These data may be ignored.)