SPREADING BATH OILS

Composition and Function:

Spreading or floating type bath oils form a film of perfume and emollient oils on the surface of the bath water. Since the perfume is on the surface, the fragrance is quite noticeable. As the bather emerges from the bath water, a layer of perfume and emollient oils adheres to the body, affording a pleasing fragrance and causing a pleasant emollient feel on the skin. Because of their spreading action, such bath oils can also be used by patting them on to wet skin after a shower.

They usually contain perfume oils at a level of 5% to 10% but may contain as much as 20% or more. The vehicles may be vegetable or mineral oils, liquid fatty alcohols, liquid fatty acids, or synthetic fatty acid esters. Some of the most popular are mineral oils, oleyl alcohol, ispropyl myristate and isopropyl palmitate. Emollients such as lanolin and lanolin derivatives are frequently added.

Formulation:

A surfactant in a floating bath oil should act as a spreading agent for the oil, eliminating the unattractive appearance of large individual oil droplets on the water surface, and providing more uniform deposition of the oil on the body. It may also function as an aid in rinsing the oil from the bathtub. In some cases, it may increase the solubility of the perfume oil in the vehicle.

To formulate a spreading bath oil with optimum functionality, it is necessary to consider the physicochemical requirements for spreading emollient oil films. For best performance, the surfactant should provide a positive spreading coefficient; that is, Spreading Coefficient = Surface Tension of H20 - Surface Tension of oil - interfacial Tension of water/oil.

(S.C. = S.T.H²0 - S.T.oil - S.T.oil/H²0).

72dynes/cm - 30dynes/cm - 0

As the magnitude of the spreading coefficient increases, the surface area which a given amount of bath oil can cover increases. The spreading velocity is directly proportional to the spreading coefficient divided by the viscosity of the liquid on which the oil is spread. Consequently, a high spreading coefficient is desirable in formulating a bath oil. A value of approximately +45 appears to be optimum. This can be obtained by using a very efficient surfactant and an oil with a low surface tension.

The HLB system of surfactant selection can be a useful guide in choosing a surfactant for use in formulating a spreading bath oil. The value of the spreading coefficient increases with increasing HLB. Therefore, the surfactant chosen should have the highest HL consistent with solubility of the surfactant in the oily vehicle.

ARLATONE T PEG-40 Sorbitan Peroleate has proved to be a spreading agent of unusually high efficiency with a variety of oily vehicles. It has an HLB value of 9, and is soluble at levels up to 10% in vegetable oils, isopropyl esters, oleic acid, and in some mineral oils. Not only does ARLATONE T spread oil homogeneously over the water surface and deposit a uniform emollient oil layer on the skin, but it also minimizes the ring which forms when the tub is drained. It is effective at concentrations as low as 1%, lower than that required with most spreading agents. The effective concentration range for spreading is about 1% to 3%. More than 3% causes the bath oil to emulsify.

ARLAMOL E combines unique emollient qualities with the ability to solubilize immiscible liquids or perfumes. Formula B-1 is an excellent example of a basic spreading bath oil containing ARLAMOL E as the emollient with ARLATONE T as the spreading agent.

Preparation:

Mix well, Filter if necessary.