Unflavoured Gelatin Shampoo Additive: For strengthening hair, increase the protein content of shampoo with gelatin! Gelatin is a great way to instantly thicken hair. It coats each strand and gives hair volume after the first use. Pour one package of unflavored gelatin into your normal shampoo. Shake well and use as often as you wash hair. The gelatin shampoo will add texture to thin hair.