How to formulate like a pro!

Jane is responsible for teaching skincare and haircare formulation at a UK University’s Cosmetic Science Degree.  Below are Jane’s top tips and tricks to take your formulation knowledge to the next level:-

1. Unfortunately there are very few credible formulas, courses, books and websites which contain scientific, safe and knowledgeable information for formulators to learn their trade. We have scoured the marketplace, internet, e-books, supplier websites and asked a multitude of respected cosmetic chemists in order to bring you the best of the most professional and respected resources out there. The following websites and courses are recommended, itsallinmyhands (for surfactant formulations), swiftcraftymonkeylotioncrafterchemistscorner, and for a useful article click here.  For a list of respected cosmetic science books click here.

2. Use distilled water or deionised water as these are more “pure” instead of water from the tap or faucet or mineral water which contains additional chemicals and impurities that can shorten a product’s shelf life and cause instability and preservation issues.

3. Professionals always measure by weight as opposed to volume.  This means a scale must be used to measure all ingredients.  Formulas listing drops, cups, teaspoons are a sign that the writer is not aware of basic scientific principles.  Measurements in volume result in inaccurate, inconsistent batches and the specific gravity of each ingredient is not taken into account.  For example, one cup of one type of oil will weigh differently from a cup of different oil due to specific gravity differences. On top of this, drop sizes, and therefore the weight of those, vary greatly.  Professional formulas should always start in percentages and then are converted to the required batch size (weight).  Percentages allow formulators to make sure the ratios between the ingredients are as desired, be able to scale up and down accurately and know how much of an ingredient is appropriate.  For example, we know that for most people if glycerin is added at more than 3% it can feel sticky.  Our popular downloadable formulation calculators can be used to convert from percentages to weight. 

4. Vitamin E is an antioxidant, not a preservative and extends the life of oils slightly. Three chemists in our discussion group have provided their views on how to use this ingredient and the consensus is usage levels are very low, at only 0.05% – 0.1%. The three chemists agree that if more than 0.1% vitamin E is included in the formula, the formula may undergo a pro-rancidity reaction.  To read more about this, join the making skincare group and look out for the graphs and data provided by the Chemists, Mirta, Tammy and Martin in this post and this post.  It should also be noted that vitamin E should be added to the oil phase, rather than the cool down phase and that the acetate form of vitamin E is not an antioxidant for the oils.

5. Many formulators estimate their product’s shelf life, assuming it is effectively preserved, by examining the shelf life of each ingredient in the formula.  The ingredient which will expire first is taken as a very rough guideline of the product’s general shelf life. In the cosmetic industry, however, a 3 month stability test should be performed to give a more accurate indication. As any changes in a lotion will take place faster at higher temperatures, samples are put at different environmental conditions which include a range of temperatures from 4°C (39°F) to 40-45°C (104°F-113°F). Typically the samples are checked at 2, 4, 8 and 12 week intervals. If the product has changed little in 8 weeks at elevated temperatures, it will likely last for a year at room temperature.

6. Balms and butters which do not contain water frequently suffer from hard white grainy spots.  They can also be very oily and melt in the Summer heat.  These are common issues for many formulators.  To solve melting issues, increase your product’s overall melt point by removing some liquid oils and replacing them with a higher melt point ingredient such as cocoa butter or 5% behenyl alcohol. If your product is too oily, replace some of the liquid oils with macadamia or hazelnut and replace some of the butter with mango butter.  If your product is suffering from grainy, hard white spots this is due to the butters and waxes containing varying amounts of fatty acids which have different melting and solidification points. Melting does not therefore happen at a single point as different components solidify/crystallize at different temperatures. Unless there is provided a uniform temperature throughout the whole, some ingredients crystallize and cause graininess or grittiness resulting in white hard spots throughout the product. A controlled cool down and stirring during the cool down stage can help avoid graininess in balms and butters. This is known as “tempering” and is often used in chocolate making. The process of tempering involves melting the product completely, (i.e. to 70°C) and then pouring it into the container and placing into a fridge or freezer (or in manufacturing, a “cooling tunnel”) to speed up cooling. Another method to reduce graininess is to use the Lipex range by the supplier AAK AB and microcrystalline wax instead of natural waxes. The suppliers of Softisan® 378 (INCI Name, Caprylic/Capric/Myristic/Stearic Triglyceride) also claim their ingredient when incorporated into a formulation will reduce graininess.

7. What is the difference between emulsifiers and solubilizers?  Solubilizers and high HLB emulsifiers are both surfactants and help to disperse oils in water. Solubilizers are more water soluble than emulsifiers and are used to incorporate very low level, usually less than 2% total lipids, into an aqueous formula such as a shampoo, shower gel, toner to obtain a transparent formula. The aim is usually for the formula to be clear, unlike an emulsion (with emulsifiers) which contains substantially more oils and is usually white. If the particle size of the dispersed (oil) phase is <100 nm, the dispersion normally appears clear. Typically these dispersions are used to solubilize fragrance oils into water based products and have a particle size of ~5nm. The key historic benchmark solubilizer is PEG-40 hydrogenated castor oil.  For recommended natural solubilizers click here.

8. Oils, including essential or fragrance oils, do not mix with water (nor aloe vera gel which is mainly water), without the help of a solubilizer or emulsifier. If the formula contains a small amount of oil soluble ingredients, for example, less than 4% and the goal is for it to be clear and the oil properly incorporated it will need a solubilizer rather than an emulsifier.  Examples include water based perfume, shower gel, shampoo, gels and toners.  Peg-40 hydrogenated castor oil is the gold standard solubilizer, with polysorbate 80 being second choice. For recommended natural solubilizers click here.  Different oils need differing amounts of solubilizer depending on how polar that particular oil is.  A starting guide is to mix directly 3 parts of peg-40 hydrogenated castor oil to 1 part oil.  This will then be added to the water.  If the water is still cloudy, add more peg 40 hydrogenated castor oil until it is clear. Do not forget to add a broad spectrum preservative blend.

9. With so much scaremongering around, how do you really know if an ingredient is “safe” and “natural”?  Cosmetic chemists despair at the likes of EWG which is considered very unscientific and biased and instead access sites such as this which provides  scientific, expert advice on cosmetic ingredients.  In Europe, the European Scientific Committee for Consumer Safety consists of an impartial panel of doctors and toxicologists and also provides detailed reports on the effect of ingredients.  To access their cosmetic ingredient reports click here.  It should be noted there is no agreed definition of natural/organic.  When making the decision as to whether an ingredient is “natural” or “organic”, consider which chemical processes to create that ingredient are acceptable, if any? An example of a chemical process is hydrolysis of an ester under basic conditions to form an alcohol and the salt of the acid. This sounds very “chemical” and synthetic to most people, however, an example of this chemical process is making soap (saponification).  As it takes a great deal of technical knowledge and time to investigate each ingredient fully, most formulators look up the ingredient in question on various websites, such as USDA Organic, Wholefoods, NPA, COSMOS.  These natural standard organisations have investigated these ingredients, analysing and rating them along several parameters, including the origin, sustainability and processing.

10. Ingredient suppliers want to sell ingredients.  They produce impressive fancy brochures with graphs and data showing how “effective” their product is.  Chemists learn from experience that most of the time these ingredients do not, unfortunately, live up to their promises.  “Self-emulsifier blends struggling to emulsify, “natural” preservatives failing preservative tests, and the like.  Assessing the effectiveness of emulsifiers and preservatives can be carried out using the standard preservative and stability tests.  However, when it comes to assessing whether an active ingredient has any effect, the following criteria is used by scientists: 

A.  Can the active ingredient penetrate the stratum corneum and be delivered in sufficient concentrations to its intended target in the skin over a time course consistent with its mechanism of action?
B.  Does the active ingredient have a known specific biochemical mechanism of action in the target cell or tissue in human skin?
C.  Are there published, peer-reviewed, double-blind, placebo-controlled, statistically significant, clinical trials to substantiate the efficacy claims?

(Kligman D. Cosmeceuticals. Dermatol Clin 2000; 18:609-615).

11.  pH strips and pH papers are, on the whole, very inaccurate.  A pH meter such as this one is therefore recommended.  If, however, pH strips must be used, the ones which we found most accurate by a long way is this. For formulators in Europe these can be purchased here.  For instructions on how to change pH click here.

12.  Formulas should add up to 100%.  For products which contain water, as water is the solvent it is usually used to make the formula add up to 100%.  For example, if all ingredients excluding water total 30%, this will mean the water amount will be 70% so that the formula’s percentages add up to 100. If, for example, all ingredients excluding water total 20%, this means the water will be 80%.  This is because 20 plus 80 is 100. 

13.  Honey is water soluble and needs an emulsifier to be successfully incorporated into an anhydrous product, such as a balm.   

14. Sunscreen. It takes many years of training for a chemist to become familiar with how to formulate this type of product which is classed as a drug in the USA. Even the most experienced chemist cannot predict the end SPF and has to rely on special tests being conducted such as ISO 24443 / COLIPA 2011 (COLIPA Ratio) or Boots Star Rating (Revision 2011), FDA Final Rule 2011 or AS / NZS 2604. To be effective the sunscreen needs to cover both UVA and UVB and in order to achieve this varying combinations of UV filters are used. The filters chosen must be: (a) properly solubilised, usually achieved through the use of esters known for this property with a sufficiently high oil phase. Crystallisation of solid organic filters can occur which reduces SPF, stability and the sensory of the formula, (b) not react with the other ingredients in the formula, (c) be photostable and not degraded, (d) be within legal limits, some UV filters used in the EU are not permitted in the USA, (d) be homogeneously and evenly dispersed throughout the emulsion which, especially for zinc oxide is very challenging even with a Silverson homogenizer, (e) zinc oxide is also incompatible with many ingredients and tends to migrate thereby increasing pH and forming alkaline Zn complexes and agglomeration resulting in significantly reduced SPF and instability, (f) the right ratio of UVA and UVB filters should be chosen for the sunscreen to be broad spectrum.  On top of this emulsifiers, thickeners, emollients, polarity of ingredients, film formers in the formula will affect the end SPF. In addition some preservatives are deactivated by UV filters. An even film over the skin is needed in order for the UV filters to be effective so application thickness, spreadability, absorption and emulsion size also affect SPF.

15. Preservation

A. If a product contains water, (aloe vera gel, tea, hydrosols, milk are mainly water), a broad spectrum preservative blend should be added.  Our preservative article contains strategies to effectively preserve your product and provides reviews of preservatives.

B. Ingredient suppliers want to sell their ingredients and so often advertise producing, “data” showing their “natural” preservative as being effective and broad spectrum.  Unfortunately, however, this is frequently not the case. Our preservative article reviews natural and synthetic preservatives so a more informed decision may be made.

C. Vitamin E, benzoin, grapefruit seed extract and rosemary extract are antioxidants, not preservatives.  Antioxidants do not protect against gram negative bacteria, gram positive bacteria nor mold.

D. It is not possible to rely on sight nor smell to know if a product is contaminated.  Home preservative test kits are very inaccurate.

E. Anhydrous (no water) products do not need a preservative unless there is a possibility that water could be introduced.

F. Products labelled “preservative free” are not truly preservative free.  The product either: (a) is not preserved properly; or (b) fails to list the preservatives in the product on the label; or (c) if the preservative has a dual function, the seller is relying on the other function to describe the ingredient. Less frequently, the seller is relying on a high level of glycols or alcohols to help preserve.

G. Heating and holding the water phase of your emulsion at 75°C/167°F for 20 minutes will help reduce the level of non-endospore forming bacteria.

H. One of the most frequent reasons for a preservative test failing is due to the formula containing high levels of food for microbial growth. Examples include fruit, botanicals, tea, lecithin, mineral water, milk of any kind, honey, hydrosols, floral waters, aloe vera, extracts, protein, clay, powders, starches etc.  It is possible to include, for example, 50% aloe vera or hydrosol in a formula and still pass preservative tests if the formula is carefully formulated with that in mind and the supplier’s copy of the micro testing for the batch of aloe/hydrosols in the formula (could be in the Certificate of Analysis) shows that ingredient is less than 100 cfu/gram or ml and no staphylococcus aureus, candida albicans or gram negative bacteria.

16. Lotions and creams.  Our lotion, creams tutorial provides key formulation advice and starting formulations.  Some essentials:

A. The correct amount of emulsifier depends on the amount of oils in the formula.  A starting point for most emulsifiers is to add the emulsifier blend at approximately 25% of the total of the oil soluble ingredients, subject to a minimum of 3% and a maximum of 7%. Oil soluble ingredients can also be found in the cool down phase so these should be taken into account in the calculation.  For more information click here.

B. Always use two stabilisers, thickeners to give your lotion the best chance of remaining emulsified through temperature changes and over its shelf life.  A minimum of 2% cetyl alcohol is generally added, together with 0.3% xanthan gum. It should be noted that xanthan gum is incompatible with cationic emulsifiers such as BTMS.  In this case, 0.3% cationic guar may be included.

C. A lotion needs high shear, such as a stick blender, or homogenizer in order to make the particle sizes as small and as even as possible for a more stable emulsion.

D. Use two effective emulsifiers, rather than one.  Beeswax and cetyl alcohol are not emulsifiers.  Emulsifying waxes vary greatly and some do not emulsify at all.  It should be noted that ingredient suppliers want to sell ingredients and often give the impression that their “natural” emulsifier is very effective when it is far from the case. For more information on this and which emulsifiers to use click here.

E. When water is heated it evaporates.  Chemists make up the lost water by adding most of the estimated loss of water into the water phase with the other water phase ingredients.  Every time a batch is made a different amount of water will evaporate so this cannot be predicted accurately in advance.  Water also evaporates while the lotion is cooling down until the point at which it is bottled.  Just before the lotion is bottled, the lotion is weighed and the remainder of the lost water is added. For more details on how to make up for water evaporation and to ask questions, after joining the making skincare group, click here.

F. Gums are water soluble and can suffer from clumping.  To avoid this many formulators pre-mix gums in glycerin before adding to the water phase.  Gums can also be added to the oil phase to minimise clumping.

G. To make a lotion thinner, deduct 1-2% cetyl alcohol or stearic acid.  You may also wish to change your emulsifier one which is much thinner, click here and here for those sold in the USA and here and here for those sold in Europe.  You will however need to keep a minimum of 2% cetyl alcohol, together with 0.4% xanthan gum in your formula for stability. To make a lotion thicker, richer and more creamy, add an extra 1-2% cetyl alcohol or stearic acid.  Viscosity can also be adjusted by increasing or decreasing gums and polymers as required. It should be noted that stearic acid is not a popular thickener in industry as it tends to be more draggy than cetyl alcohol and contributes less to stability.

H. To make a lotion less sticky, reduce the level of glycerin and panthenol. If it is still sticky, reduce the level of gums and polymers, however it is advisable to keep a minimum of 0.2% xanthan gum in your lotion for stability purposes.

I. To make a lotion less greasy, reduce the overall level of oils and butters and change out the oils and butters for dry feeling ones such as mango, hazelnut, macadamia, isoamyl laurate, dicaprylyl carbonate, isododecane, isohexadecane, dodecane.  Cetyl alcohol or stearic acid can also be replaced with behenyl alcohol.

J. To increase the spreadability of your lotion, reduce the level of stearic acid, cetyl alcohol and waxes but for stability do include a minimum of 2% cetyl alcohol.  Replace the oils and butters with quick spreading esters such as hemisqualane, dicaprylyl ether, coco caprylate, dicaprylyl carbonate, isohexadecane.  You may also wish to change your emulsifier for a less waxy type – click here and here for those sold in the USA and here and here for those sold in Europe.  These emulsifiers are, however,  quite thin so extra cetyl alcohol should be added (minimum level 2.5%, ideal level 3% or more), together with 0.5% xanthan gum for stability.

K. To make your formula more moisturizing, increase the percentages of the oil phase ingredients and also glycerin.  Add occlusive ingredients such as lanolin, dimethicone, cocoa butter to help guard against transepidermal water loss.