Preparation of Shampoo: A simple procedure is involved in the preparation of shampoo. Initially, only one method was available for the preparation of shampoo, but later the basic method was modified to obtain a different type of shampoo like cream, gel, aerosol, etc.
Formulation of Liquid Shampoo
General Method for Preparation of Shampoo
The liquid shampoo is usually prepared by this method which involves the following steps:
- Initially, the detergent is converted into a solution form or a detergent solution may be directly obtained from the manufacturer.
- Take about half of the detergent solution into a separate container. To it, add the total amount of secondary surfactant i.e., alkanol amide.
- Dissolve the alkanol amide along with stirring. Sometimes, gentle heat is also applied.
- To the remaining half of the detergent solution add a suitable amount of perfuming agent and dissolve it.
- The perfume solution is then added to the alkanol amide solution.
- Colour and preservatives are dissolved separately in a sufficient volume of water and then added to the main solution.
- The whole solution is mixed well by gentle stirring. Excessive stirring may lead to bubble formation.
- The final volume of the preparation is usually adjusted by the addition of clear sterile water. This gives clear liquid shampoo.
- However, when the preparation contains lauryl alcohol ether sulfate. It is required to adjust the viscosity of the shampoo.
- Viscosity adjustment is done by using an electrolyte solution. Usually, a solution of sodium chloride is added subsequently with constant stirring. Care must be taken to prevent the excess addition of sodium chloride.
Methods of Preparation
The methods of preparation of various types of shampoos are modifications of the above-mentioned general method of preparation of shampoos.
Formulation of Cream Shampoo:
Preparation of Cream Shampoo: Certain formulae of cream shampoo may include glycol stearate or waxes. Usually, glycol stearate is used as an opacifier and the preparation method for such formulae is similar as discussed above. But when the wax is included in the formula, the process involves the following steps.
- Initially, a solution of detergent and water is heated to about 80°C.
- The wax is heated separately in a container at 80o C which facilitates the melting of the wax.
- Both the solution is kept at 80°C and mixed. Uniform mixing is achieved by constant and gentle stirring.
- The solution is allowed to cool about 40 to 45°C
- Finally under warm conditions mixture is transferred to suitable conditions.
Formulation of Gel Shampoo:
Preparation of Gel Shampoo: The method involved in the preparation of gel shampoo is similar to the clear liquid shampoo. After preparation the liquid shampoo is usually treated with a suitable thickening agent and a gelling agent such as hydroxyl propyl-methyl cellulose, this gives the gel consistency.
Evaluation of Shampoo
Shampoos are evaluated for the following aspects.
- Evaluation of safety
- Evaluation of anti-microbial property
1. Evaluation of Safety:
Safety is an important aspect that must be considered as the first and foremost parameter of evaluation. As stated earlier, shampoos are made from synthetic detergent which irritates the skin scalp, and eyes.
(a) Draize test: Safety is determined by using the Draise test which suggests two separate methods for testing skin and eye toxicity. The following steps are involved in the test:
- Six albino rabbits were selected weighing 2 kg.
- The round patch is made on each rabbit’s skin by removing hair.
- Apply to dilute preparation of shampoo on each patch.
- The shampoo will react for 2-3 hr and then it is removed.
- After washing the skin is examined for any irritation
- Based on the result obtained shampoo is evaluated as safe or toxic.
(b) Eye-toxicity test: The following steps are involved in the test:
- Six adult albino rabbits are selected
- One eye is considered as a test and another as a control eye.
- To each eye, the product is applied.
- Washing is done with tap water for 20 seconds.
- The eye is rewashed after 5 minutes and then after 24 hours.
- The control eye is also washed on the first day and then after 24 hours.
- The test eyes are observed at 1, 24, 48, and 72 hours respectively.
- The product is considered to be toxic if there is a development of iris and corneal lesions which remain for more than 7 days.
2. Evaluation of Anti-microbial Activity:
The shampoo is liable to microbial growth because it is liquid or viscous. So preservative is usually added to stop such growth.
Evaluation of preservatives usually involves the study of anti-microbial activity. This is usually done by a method called “challenge study”.
Procedure for Challenge Study:
- Species like pseudomonas are selected.
- A culture of any one of the test organisms is prepared.
- The product is inoculated in culture media for 10-12 weeks.
- Inoculums usually contain 5 lakhs to 1 crore microorganisms.
- Two types of samples are prepared, one with preservatives and one without preservatives.
- The test concludes only when it has been proven that the product has not supported microbial growth.
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