Making Creams Part 3

Using Esters in Creams and Lotions

Whilst using natural plant oils is seen as a positive in terms of the marketing of skincare products, creams featuring high proportions of plant oils do not necessarily make elegant products with a pleasant skin feel.

If plant oils comprise all of the oil phase then the cream may feel heavy and greasy on the skin and may not absorb particularly well. Creams with a high plant oil content tend to also provoke the whitening effect whereby the cream breaks when applied to the skin leaving a white residue which can take time to absorb into the skin.

Manufacturers typically add silicones to the formulation. Silicones provide several sensorial benefits to a cream. They can offset greasiness from plant oils, improve the slip and spreadability of the cream, improve absorption of the cream by the skin, and can offset the whitening effect.

However, with the increasing demand for ever more natural skincare products consumers are preferring to avoid creams and lotions which contain mineral oils and silicones.

Fortunately esters provide an alternative to silicones and, as many currently available esters are Ecocert approved, you can look to improve your formulations without compromising your products' natural claims

What are esters?

A compound formed from the reaction between an alcohol and an acid via the elimination of water. Triesters (groups of three esters) form the backbone of many fats, waxes, and oils that have emollient and skin-conditioning properties (Source: A Dictionary of Chemistry, Third Edition, Oxford Paperback, 1996). Almost all of the esters used in cosmetic products are non-irritating and in most cases are quite beneficial for dry skin.

Why Use Esters?

Creams and Lotions based entirely on plant oils can feel greasy and heavy on the skin. They can also be difficult to absorb and more often than not can provoke the phenomenon known as soaping when the cream is applied to the skin (the emulsion breaks leaving the water to absorb into the skin and leaving the emulsifier and oils on the surface

What are the properties of esters?

Esters offer the opportunity to fine tune your cream or lotion to achieve the skin feel you want.

Esters can determine how light or rich your cream is. Esters come in a variety of 'weights' from very light to very rich. If you want to create a rich luxurious night cream choose an ester from the heavy end of the scale such as Aprilose. If you want to create a very light 'invisible' day cream then choose a very light ester such as Propanediol Caprylate.

Esters can also determine the play time of the cream. Consumers might want a day cream that is fast absorbing and so would want a cream with a short play time (the amount of time the cream has to be massaged into the skin). For a luxurious night cream a longer play time might be preferred to increase the sensorial experience of massaging the cream into the skin.

Esters can also help determine the after feel of the cream - i.e how the skin feels after the cream has absorbed into the skin.

Certain esters can leave a soft powdery after feel (like how the skin feels after applying talc), others can leave a slight oily residue – preferable for night creams when the customer wants to feel they have a rich cream on their skin.

How to Use Esters

Esters are direct replacements for oils. If your cream contains say 15% plant oils then you can replace any amount of plant oil with an appropriate ester or blend of esters. There's no hard and fast rule about proportions of oils to esters but generally I like to use a 50-50 blend so I would reduce the plant oils down to 7.5% and add 7.5% esters. The choice of esters being determined by the skin feel I was hoping to achieve.

To keep things simple (until you become more familiar with the properties of different esters) I recommend you experiment by using one of the most popular and most commonly used esters - C12-15 Alkyl Benzoate. C12-15 Alkyl Benzoate is a light to medium weight ester which provides a light conditioning and silky after touch to the skin.

So in our standard formulation I would reduce the Almond Oil by 4% and the Hazelnut by 2% as I want to keep the extra emolliency of the Shea Butter in our recipe. I'll adjust the reduction of the Almond and Hazelnut Oils by adding 6% C12-15 Alkyl Benzoate

Our original formulation

Water Phase
Water	79.70%	797g
Xanthan	0.50%	5g
	80.20%	802g
Oil Phase
Sweet Almond Oil	9.00%	9.00g
Hazelnut Oil	4.00%	40g
Shea Butter	2.00%	20g
Emulsifying Wax	4.00%	40g
Cetyl Alcohol	0.8%%	8g
	19.20%	192g
	100.00%	1000g

Is adjusted to incorporate the esters and becomes:

Water Phase
Water	79.70%	797g
Xanthan	0.50%	5g
	80.20%	802g
Oil Phase
Sweet Almond Oil	5.00%	9.00g
Hazelnut Oil	2.00%	40g
Shea Butter	2.00%	20g
C12-15 Alkyl Benzoate	6.00%	70g
Emulsifying Wax	4.00%	40g
Cetyl Alcohol	0.8%%	8g
	19.20%	192g
	100.00%	1000g

With these adjustments the final product would have more slip, feel more elegant, less greasy, should absorb more easily, and reduce whitening (though it won't be eliminated completely).

Making Creams Part 2

In the previous article we looked at making a very simple cream following the 80:15:5 ratio for Water:Oil:Emulsifier. The formulation was just about as simple as it gets and here we're going to look at how we can tweak the basic recipe to improve the feel and stability of the cream

Emulsifiers will provide body to the cream but using emulsifiers on their own to thicken the cream is not ideal. There are a variety of materials available to the home formulator that can increase the viscosity of a simple emulsion.

Water Phase Thickeners

Are naturally derived polymers that work by absorbing water to swell up and increase viscosity. Cellulose derivatives like Hydroxyethylcellulose are frequently used in a variety of skincare products. Guar gum is another example of a naturally derived thickener. Others include Locust Bean Gum, and Xanthan Gum. There are many more but they may be difficult to source.

They are supplied as powders and are added to the water phase.

There will be many articles available explaining the best methods for incorporating these powders into the water phase – from first mixing the powder with a little glycerine, sprinkling onto cold water and allowing the polymers to swell before them using a high speed mixer to blend. Personally I simply sprinkle the powder into the heated water phase under the action of a high speed stick blender.

Water thickeners do not just build viscosity in the cream they also help stabilise the emulsion.

Xanthan – Readily available and easy to use. Usage rate is typically 0.5% to 1% though more can be used if desired. However above 1% Xanthan Gum can make your cream a bit stringy

Hydroxyethyl Cellulose (HEC) - not as commonly used as Xanthan but ought to be fairly easily available online. Usage rate is typically 0.5% to 1%. I prefer HEC to Xanthan as I find that creams using HEC as the water thickener have a nicer skin feel. HEC will also make crystal clear serums – if used at 1%. HEC will also tolerate alcohol very well and so can be used to make your own sterilsiing gel.

Guar Gum – is a highly effective water phase thickener that works well in creams. Use at 0.3% to 0.5%.

Ecogel - Lysolecithin (and) Sclerotium gum (and) Xanthan gum (and) Pullulan

is a relatively new addition to the range of water thickeners. It is in fact a blend of 4 thickeners which work synergistically to create a sophisticated multi-function agent. Not only will Ecogel act as a water thickener and emulsion stabiliser, it is capable of acting as an emulsifier. It is possible to create gel creams with a light and sophisticated skin feel. As a water thickener Ecogel can be used at between 0.3% and 1% and is compatible with a wide range of emulsifiers.

For more information click here:

Lecigel

is a gelling agent with emulsifying properties. It allows the increase in the viscosity and the stability of formulas. Suitable for both cold and hot processes, it also helps to adjust the viscosity at the end of the formulation process. Easy-to-use, it is compatible with most emulsifiers and is stable over a wide range of pH

For more information click here:

Oil Phase Thickeners

Tend to be selected from three groups of chemicals – Fatty Acids, Fatty Alcohols, and Butters.

(Note these 'acids' and 'alcohols' are not the same as we generally understand acid and alcohols).

There are a wide range of fatty acids and alcohols available for use in skincare but for the home formulator the following are usually easily available.

Stearic Acid (Fatty Acid) - can be derived from a variety of sources notably from natural butters such as shea and cocoa. Stearic Acid builds viscosity in a cream and also improves it's stability

Add to the heated oil phase at 1% to 2%.

Cetyl Alcohol (Fatty Alcohol) - Used as an emollient, thickener, or co-emulsifier in creams and lotions. It imparts texture and viscosity to creams and lotions. It is also used as an opacifier in shampoos. Please note that Cetyl Alcohol is not suitable for use as a stand alone emulsifier. It's role is to stabilise or thicken emulsions where a primary emulisifier (Emulsifying Wax blends, Olivem 1000 etc) is used.

Add to the Heated Oil Phase at 1% to 2% (3% can be used but tends to degrade the sensory feel of creams)

Cetyl Esters

Cetyl Esters is a blend of fatty alcohols and fatty acids that offer an easy way to increase the viscosity (thickness) of your creams and lotions while also improving the feel. The blend may include cetyl stearate, cetyl myristate, cetyl palmitate, myristyl myristate, and myristyl stearate. They are derived from vegetables,

Cetyl esters can be used anywhere you might use cetyl alcohol, although they will offer different qualities from the fatty alcohol. Using cetyl esters in a lotion or cream in the place of cetyl alcohol will give you a silkier feeling and a slightly thinner product. It will also lend stability to the emulsion.

Add to the heated oil phase at 1% to 2%.

Butters – because butters contain a high amount of stearic acid (and other fatty acids) for a more natural ingredients listing you can use plant derived butters (shea, cocoa, almond, etc) in the heated oil phase to add body to your cream. Using butters will give a more luxurious and richer feel to your cream. Bear in mind that butters should form part of the calculation for the oil phase. So if you are using 15% oil content and want to include say 2% Shea Butter reduce the liquid oils by the same amount. Limit the amount of butter to 3% as levels above 3% can make the cream feel grainy.

So let's trying modifying our basic formulation

Our original recipe was as follows

Water Phase
Water	80.00%	800g
Oil Phase
Sweet Almond Oil	10.00%	100g
Hazelnut Oil	5.00%	50g
Emulsifying Wax	5.00%	50g
	100.00%	1000g

We're going to use Xanthan at 0.5% as a water phase thickener and cetyl alcohol at 1% as an oil phase thickener. As we had used Emulsifying Wax at 5% to acts as the emulsifier and to provide body to the cream we are going to reduce it by 1% as the cetyl alchol will contribute thickness to the cream

Our new formulation is as follows

Water Phase
Water	79.50%	795g
Xanthan	0.50%	5g
Oil Phase
Sweet Almond Oil	10.00%	100g
Hazelnut Oil	5.00%	50g
Emulsifying Wax	4.00%	40g
Cetyl Alcohol	1.00%	10g
	100.00%	1000g

If we wanted to use butters in our formulation we would reduce the amount if oil by a proportionate amount and we could reduce the amount of cetyl alcohol a little to offset the extra body provided by the butter. Of course if we wanted a richer, thicker cream we could keep the cetyl alcohol at the same amount.

Water Phase
Water	79.70%	797g
Xanthan	0.50%	5g
	80.20%	802g
Oil Phase
Sweet Almond Oil	9.00%	9.00g
Hazelnut Oil	4.00%	40g
Shea Butter	2.00%	20g
Emulsifying Wax	4.00%	40g
Cetyl Alcohol	0.8%%	8g
	19.20%	192g
	100.00%	1000g

The best thing to do is to experiment. Try making small adjustments to the levels of oils, emulsifiers, and thickeners to obtain the viscosity and thickness you want.

Next article. Enhancing the cream – additional water phase and oil phase ingredients