Case study: Powder texture measurement for makeup

PRINCIPLE OF THE TEST

Evaluate the hardness of a face powder using a 2mm cylindrical probe.

CONTEXT

The most popular form of face powders today is in the form of compact tablets. Texture, shade and fragrance are the three key characteristics of a face powder that are important to a manufacturer and the most obvious characteristics to a customer.

The basic ingredient of the volume compressed powder is talc, a natural hydrated magnesium silicate constituting up to 70%. % or more of the powder. The talc gives the powder a "slippery" and silky feel, making it soft and easy to apply. The additional use of binders and other raw ingredients impart color, fragrance and stability to the compressed powder by preventing it from crumbling, cracking and forming dust during transportation and use.

The texture of the face powder should be consistent from purchase to purchase. The choice of ingredients and their respective amounts is therefore important and will affect the hardness of the powder and the ease with which the powder packs (caking).

The penetration test assesses these properties by measuring the hardness or "cake strength" of the compressed powder using a cylindrical probe attached to the CT3 texture analyzer.

METHOD

Equipment: CT3 with 4.5 kg load cell

Cylindrical probe 2 mm (TA 39)

Round base table (TA-RT-KIT)

Texture Pro CT software

Settings:

Type of test: Compression

Pre-test speed: 0.5 mm / s

Test speed: 1.0 mm / s

Post-test speed: 4.5 mm / s

Target type: Distance

Target value: 2 mm

Trigger force: 5 grams

Note: It is recommended that the pre-test speed be the same or slower than the test speed for accurate trigger detection; for example, a test speed of 1 mm / s will require a pre-test speed ≤ 1 mm / s.

The penetration distance can be changed; however, the chosen target distance should be such that the probe does not touch the base of the container. Otherwise, the instrument will be overloaded and results may vary.

PROCEDURE

1.Attach the round base table to the base of the instrument and tighten lightly with the thumbscrews to allow some degree of mobility for the alignment phase.

2.Attach the cylinder probe to the load cell

3. Lower the cylindrical probe a few millimeters above the sample surface and align the sample in the center below the cylindrical probe.

4.The knurled screws of the base table can now be tightened.

5. Start the penetration test.

6. Make sure the cylindrical probe is cleaned afterwards using a dry cloth to remove any adhering powder before the next sample test.

RESULTS

A typical Texture Pro CT software plot measuring the hardness of a face powder.

Figure 1: The graph shows the hardness of a face powder using a 2mm cylindrical probe tested at 21C.

Figure 2: The graph shows the load versus distance for the hardness of a face powder. The probe starts one millimeter above it, enters the sample at a distance of 2 mm, after which it withdraws from the sample at a post-test rate of 4.5 mm / s and returns to the starting position above the sample surface.

OBSERVATIONS

From Figure 1, there is an increase in force as the probe enters the sample to the point where the sample surface begins to crumble. This is the first peak value shown in the graph. Once the surface is penetrated, the measured force increases steadily until a second maximum value is measured. The higher the penetrating force, the more compact the powder.

The test can be used to compare different powder formulations or different lots of the same brand. In the case of tests on different batches of the same product, the differences in penetration forces may reflect the differences in compression times during manufacture.

Typical average values for hardness and hardness work performed, measured at four different locations in the sample, are shown below: