Testing the attributes of hair products can be quite simple. For example, to check the color of a newly formulated hair dye, both gray and brown humanhair swatches are dyed and the results are evaluated. To check foam height of a shampoo, I put 30g of water in a 100ml graduated cylinder and one gram of the shampoo and invert 10 times using the same force. The foam height is then measured. A more accurate mechanical shaking device can be used instead.
The following procedure is a precise method to measure curl retention properties from a water-based spray, either pump or aerosol.
The curl retention properties of the hair spray resins are determined at 72°F and 90% relative humidity over a period of 24 hours. The change in percentage retention vs. time may be plotted to illustrate differences among formulations.
• 8” European brown hair
• Barber shears
• Nylon comb
• White cotton thread (size #8)
• Identification tags
• 3” x ½” Teflon Mandrels
• Forced air oven @ 120°F
• Fiberglass retention board
• Environmental chamber (precision to 2% R.H. @ 72°F)
• 10% aqueous solution of sodium lauryl ether sulfate (25% active)
Preparation of Curl Swatches
1. Separate hair into 2g swatches.
2. Tie hair sample ¾” from root end with cotton thread.
3. Fold over at root and secure the hair into a small loop with thread. Leave about 6” of loose thread to attach identification tag.
4. In order to prevent loss of individual hairs during combing, glue the root end at the thread windings with epoxy cement.Allow cement to harden.
5. Wash hair in 10% shampoo solution.
6. Comb to untangle the hair.
7. Cut the hair swatch to measure 6” in length from the loop root end.
8. Dry at 120°F.
Preparation & Exposure of Test Samples
1. Wet hair and comb through to remove snarls.
2. Squeeze out excess water by running the swatch between thumb and index finger.
3. Make hair into a coil configuration by rolling it on ½” diameter Teflon mandrel. Secure hair on mandrel with plastic clips.
4. Dry hair, mandrel and clip @120°F.
5. When hair is dry and cool, remove clips and hair from mandrel.
6. Carefully suspend the dry curls in random fashion on a graduated, clear, transparent, Plexiglas curl retention board.
7. Take initial curl height reading (Lo).
8. Remove curls from the boards and suspend the curl from the bound end in a vented area. Apply a controlled amount of hairspray as follows:
Pumps: A total of four pumps are used—two in the front of the curl and two in the back—each from a distance of 8”.
Aerosols: Suspend hair sample on a slowly rooting shaft (20-22 rpm) and spray for four seconds from a distance of 12”.
9. Lay the freshly sprayed curl on a horizontal surface and let air dry for one hour at room temperature.
10. Re-suspend the dry curls from the curl retention boards, making sure the curls are attached at the bound end in the same position as in step 6.
11. Record curl height (Lt) at 0, 15, 30, 60 and 90 minute intervals.Also at 2, 3, 4, 5, and 24 hour intervals.
Calculate percentage curl retention using:
Curl Retention =L – Ltx 100
Where: L = Length of hair fully extended
Lo = Length of hair before spray and exposure
Lt = Length of hair after spray and exposure
The curl retention value at the time zero (Lt at 0 minutes) is the comparison base to show the effect of water-based hairsprays on the curl before exposure to high humidity conditions.
Harvey Fishman has a consulting firm located at 34 Chicasaw Drive, Oakland, NJ 07436, email@example.com, specializing in cosmetic formulations and new product ideas, offering tested finished products. He has more than 30 years of experience and has been director of research at Bonat, Nestlé LeMur and Turner Hall. He welcomes descriptive literature from suppliers and bench chemists and others in the field.
Curl Retention Procedures
By Harvey M. Fishman, Consultant
Published September 7, 2010
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