We have already said that there are many natural gels and that they are still used in large quantities today. Most often, these are products of plants that are dried, but there are also those that are of animal origin.
Gelatin (INCI: Gelatin)
Gelatin gels are old types of pharmaceutically applied gels, and today they are indispensable in the industry. They are added everywhere, from vaccines to capsules, because most of today’s capsules are gelatinous. Gelatin is a protein obtained from collagen by a process of partial hydrolysis. It is not poetic, it is obtained from the skin, hooves and bones of cows, pigs and horses. But it was very practical, because these are all products that are common by-products in the meat industry. You don’t need to imagine much about what a gelatin gel looks like. If you know what pork jelly looks like, then you know what a gelatin gel is. In our house, this dish was often made, and it is obtained by cooking pork tails, legs and ears for a long time, until the gelatin comes out of the meat, which after cooling becomes a real solid gel. As far as I understand, this traditional dish is not very popular, but it’s all a matter of taste. In cooking, such a gel is also called aspic. Gelatin gel is a common ingredient in cooking because it is obtained purified.
It was once used more in cosmetics. The downside is a quick spoilage, because it is a good base for the growth of bacteria, and then it stinks quite a bit. It was also incompatible with some natural substances such as tannins. A big blow to gelatin gels was the appearance of mad cow disease, so because of the fear of the so-called BSE, it was completely replaced by different types of gels. I only mention it here because of your general cosmetic culture. Needless to say, it is completely incompatible with the COSMOS standard.
Starch (INCI: Starch)
Is it necessary to explain why starch is a gel? I guess you’ve made pudding at least once. At elevated temperatures the starch swells. In cosmetics, starch gels in glycerol are used and they are almost a matter of history. Ask your grandmothers, they may remember that there was one cream, very popular, called Borogal and it had more shapes and recipes. Today, it is still produced by Galenika, and in one of the original recipes, starch gel with boric acid was one of the ingredients. Borogal was a skin cream, today it has been replaced by more modern products, just as starch gels have been slowly supplanted by different types of gels. They are made by heating wheat starch in glycerol at a temperature over 100°C, resulting in characteristic swelling and the formation of a thick, transparent gel that was the basis for other gels and creams. They are natural, but they also have a few flaws. They spoil very quickly (if they are without preservatives), and due to the higher glycerol content, they are quite sticky and difficult for the skin. They are very hydrophilic gels and if there are no emulsifiers, in you will not be able to put them in the oil phase.
I’ve been thinking for a long time whether to describe it at all, because you’ll probably rarely make them. But I will give you a recipe for the starch gel itself- in case you like it, to keep my conscience clear. And also because of your general cosmetic culture. Of course, they are fully compliant with eco standards.
By the way, the specified INCI name is not complete. It is always necessary to specify from which plant starch is obtained:
- Triticum vulgare starch (wheat)
- Zea mays starch (corn)
- Pueraria lobata starch (kudzu)
- Oryza sativa starch
- Avena sativa starch (oats)
Wheat starch is usually used to prepare the starch gel.
Xanthan (INCI: Xanthan gum)
Xanthan is one of the most popular natural gels, used in natural and classic cosmetics. It is obtained by fermentation of sugar in the presence of the microorganism Xanthomonas campestris. It was discovered in the 1960s, when biopolymers were studied. It has been found that this sugar bacterium creates unusual chains, polymers, that swell nicely in water. It consists of sugars and acids: glucose, mannose, glucuronic acid and pyruvic acid. It is very easy to prepare, and its advantage is viscosity in acidic media, which is a disadvantage of many natural gels that are sensitive to changes in acidity (pH).
Xanthan is a very commonly used gel used in gels and creams and in the food industry, and even in construction for underwater cementation. In emulsions it prevents the joining of small sprayed (emulsified) droplets in a process called coalescence. Therefore, it is a common emulsion stabilizer. It is pleasant for the skin and does not create too strong a film. It is usually used in gels in concentrations of 0.5-1%.
We will learn how to make gels with xanthan. However, xanthan gel also has its drawbacks: like many natural gels, it can be “peeled” if it is spread in too thick a layer. It is often a xanthan gel that resembles “lumps” or “layers”, which is often expressed in shower gels.
There are multiple levels of xanthan purity. In Croatia a slightly coarser gel available, which gives more cloudy gels. Transparency grade xanthan is available outside Croatia, which gives almost completely transparent and visually very pleasing gels. Market examples are Novaxan and Grindsted xanthan. Some of them are also granulated, so they melt very easily by ordinary resuspension in water.
The pH of the 1% gel is between 6 and 7, and the viscosity is 1200-1600 mPa s.
Guar (INCI: Cyamopsis tetragonoloba gum)
Guar gum (gel) is a very pleasant gel obtained from the seeds of the plant species Cyamopsis tetragonolobus (L.) Taub. Fabaceae. The plant is wild in India and this is where the largest amount of guar is produced. The seeds are peeled and ground to obtain a white powder of varying fineness. Chemically, it is a galactomannan, i.e. a polysaccharide composed of sugar mannose and galactose. Guar gel requires the addition of calcium or borate to form a strongly thick, viscous gel, but in practice you will not need to do this. It is relatively inexpensive, used in gel creams and as a stand-alone gel, also in concentrations of 0.5-1%. As a branched molecule, it stabilizes emulsions very well. It is very often mixed with xanthan, because they synergistically help the formation of gels of good behaviour. Praised in natural cosmetics, guar gel is still more clumsy to work with, and it shows, depending on the concentration, the peeling effect. The gels themselves are more cloudy than xanthan.
The pH of 1% gel is 5-7 and the viscosity is 4.86 Pa s.
It is very similar to the carob seed gel (Ceratonia siliqua L., Fabaceae), better known by the English abbreviation LBG (locust bean gum) which gels better and without additives. However, you will rarely find it on the market in Croatia.
Tragacanth (INCI: Astragalus gummifer gum)
Tragacanth is a gel obtained from several species of plants of the genus Astragalus, the highest quality tragacanth is obtained from species A. gossypinus, А. microcephalus and A. echidnaeformis, but the most common on the market is the one obtained from type A. gummifer which is slightly lower quality. The plant grows wild in Iran, Syria and Turkey. It is obtained from the liquid in the conducting veins of the plant (“milk”), which, when dried, takes on the characteristic shape of the horns of a goat. The name tragacanth, translated from the Greek language, means: goat’s horn.
Tragacanth is slightly more expensive than xanthan, and shows similar properties. It is also used in concentrations of 0.5-1%. Its ingredient is tragacanthin, a polymer of various sugars: L-arabinose, L-xylose, L-fucose, D-galactose and D-galacturonic acid. It is very viscous and retains water and moisture very well, so it is a favourite additive in creams where, like many gels, it serves to stabilize emulsions. Apart from cosmetics, it is also used in the food industry and in the production of pastels as a binding agent.
The pH of a 1% solution is usually 5-6, which is an acidity that is pleasing to the skin. The viscosity of 1% gel varies from 100 to 4000 mPa s.
Gum arabic (INCI: Acacia gum)
Gum arabic (acacia; acacia gum) is obtained from the juice of two species: Acacia senegal Wild. (= Senegalia senegal Britton) and А. seyal Del., Fabaceae. From type A. seyal a lower quality gum is obtained and is sometimes called talh gum. The species grow in the Saharan and sub-Saharan zones of Africa and the Arabian Peninsula. The dried juice is ground for further use. Arabic gum is a very complex gel that contains both polysaccharides and hemicellulose. The chemical composition includes arabic acid and sugars arabinose, glucose, galactose and rhamnose. It also contains proteins (glycoprotein) and is therefore different from the gels mentioned so far.
Unlike previous gels, Arabic gum must be used in concentrations of 5-30% (depending on the desired density), because the gel is less viscous than, for example, xanthan. It is rarely used as a pure gel, but is mostly added to gel creams and body lotions to promote emulsification. It is also more expensive, it is used in higher concentration and therefore it is used less often in cosmetics.
Arabic gum has another drawback: it contains the enzyme peroxidase, which can oxidize sensitive oils with polyunsaturated fatty acids (such as evening primrose, borage, rose hip seed oil…). To destroy the activity of this enzyme, after dissolving the gum, heat the solution in a bath of boiling water for a few minutes, then cool. This again complicates the production, so you will use Arabic gum less often in cosmetics. Arabic gum is widely used in the pharmaceutical industry, but also for printing, photography, and of course in the food industry.
Solagum AX (INCI: Acacia Senegal gum (and Xanthan gum))
Xanthan gel is very popular in the industry, viscous but a bit “lumpy”, that is, it shows layers that some call it an unpleasant name – “snot”. On the other hand, gum arabic gives gels that are uniform and without layering, but are extremely weakly viscous. Therefore, the French company Seppic decided to combine these two gels to get a new, texturally superior xanthan and gum arabic. They succeeded enviably in that.
Solagum AX is finely granulated and disperses well in water and without rubbing in glycerol, it swells well in hot and cold water. The texture really looks like a condensed liquid and is visually very likable, only slightly opalescent. It has a lower viscosity than xanthan, but it also has an advantage: the xanthan viscosity increases nonlinearly with concentration, so even when you add only a small excess of xanthan you get too viscous a gel. This is not a problem with Solagum AX, which shows a far more linear increase in viscosity with increasing concentration. Although xanthan gel is more affordable, Solagum AX is my favourited gel in shampoos and shower gels, superior in texture to almost all other gels (at least in my opinion).
As it is less viscous, up to 3% is added to gels, but on average 1.5-2% is used. The pH of a 1% solution is 5-7.5 and the viscosity is 400-600 mPa s.
Red Algae Gel (INCI: Algae extract)
Red algae gel is obtained from red algae of the species Ahnfeltia concinna J. Agarth. Rhodophyta and we have already encountered it in tonics. Have you ever slipped on the rocks by the sea, where the rocks make small natural pools with hot water heated by the sun? You probably already know that there’s a layer of algae out there that’s damn slippery. Well, if you’ve fallen, then know that you’ve slipped on a top-notch cosmetic ingredient, even though it’s not a consolation to your backside. These are not the red algae from which the red algae gel is obtained: the red algae is a larger organism and is a Pacific species. But the composition is very similar. It is obtained biotechnologically, from cell culture and which is known, like many algae, for its strong mucus.
Red algae gel is a relative novelty, but a very pleasant novelty in cosmetics, so we will describe it in more detail. It has a complex composition with polysaccharides and proteins. The polysaccharides in this algae are called carrageenans or carrageenans, and the basic structure is the sugar galactose to which the sulfate group is often attached. It also contains amino sugars, which is quite specific for this species. Many Rhodophyta algae contain carrageenans, which are widely used in the cosmetics and food industries.
Why was this alga chosen? Ahnfeltia concinna also contains one unusual compound, 4-hydroxy-proline. It is found in our collagen (it is an amino acid). When the body “feels” that there has been an increase in the concentration of this compound, it begins to assume that there has been an increased breakdown of collagen and begins the process of creating a new one- and this is the holy grail of many cosmetics. Enhanced but controlled collagen synthesis reduces wrinkles, enhances skin tone and elasticity and simply makes the skin more beautiful. 4-hydroxyproline penetrates the skin and is absorbed, which is a great advantage over non-absorbable collagen (we’ll talk about that a little later).
Therefore, red algae gel is far more than ordinary gel- it is also an active substance, unlike most gels we have listed so far. Red algae gel has another, very practical advantage. We jokingly say that it is an American type of product- take it, mix it and the product is ready. It comes on the market in a liquid state, already ready for use, which only needs to be diluted in hydrolate or water. Probably that is the reason it will be very interesting to you. It is used everywhere, from gels, tonics (in a lower concentration it does not cause strong thickening) and emulsions, in which it acts as stabilisation agent and the active ingredient. In shampoos, it gives the hair softness and prevents electrification, but it does not make it heavier or greasy.
Red algae gel, like many algae, has a mild antimicrobial effect. I would not emphasize this less important fact, if I had not come across an interesting product- red algae gel lubricant that serves as protection against sexually transmitted diseases, especially HPV! I would not be so pretentious to think that it is exactly 100 % safe way, but the fact is that it is a really pleasant lubricant that does not bother the mucous membranes at all.
It is added to gels from 45-60%, in tonics far less, up to 5%, while for emulsion systems the concentrations of 1-5% are more than enough. Compared to the prices of other gels, red algae gel is expensive, but the action justifies every euro invested.
Knowledge and practice is also needed to make an algae gel, because in too high a concentration it becomes uncomfortable and strongly tightens the skin. Therefore, we will learn to work with it to prevent this from happening.
Hyaluronic acid (INCI: Hyaluronic acid and sodium hyaluronate)
Hyaluronic acid (hyaluronan, hyaluronate) is marketed strongly not only in cosmetics, but also as a dietary supplement to help with osteoarthritis (“joint wear”). It is used in medicine in injections given to the joints in osteoarthritis, but also in dermatology in “fillers”, in injections that “instantly” solve wrinkle problems.
It’s a huge molecule. It consists of the building blocks of D-glucuronic acid and D-N-acetylglucosamine. It is found in almost all tissues, and is especially important in cartilage, where it is both a lubricant and a shock-absorbing substance (walking, running, jumping). It has an extremely important role in the skin, because it gives it, among other molecules, elasticity, but also participates in a number of important events, such as skin regeneration.
It has been known for eighty years, but it reaped its marketing success at the end of the last and the beginning of this century. Paradoxically, intact hyaluronic acid is not absorbed through the skin at all and in principle cannot affect anything at all except the surface layer of the skin itself. Therefore, its use is seemingly meaningless. However, on the surface it acts as a protective substance and gives elasticity and moisture to the skin, and it is interesting because it makes a gel and stabilizes the emulsion and is the active ingredient. It is usually advertised in intensive regeneration agents, although this is questionable. However, creams with hyaluronic acid (and less gels) are very popular and people are subjectively satisfied with them. Science has so far come up with a lot of different ways to “push” such a large molecule into the skin, like liposomes, but these are all usually more expensive solutions completely unsuitable for simpler manufacturing.
Hyaluronic acid can be in the form of hyaluronic acid and sodium hyaluronate. It is obtained industrially from two sources. The first is from the cartilage of animals, especially interesting is the cartilage from the sternum and crest of chickens. This type of hyaluronic acid is not COSMOS compliant and is not used by vegans. Another way is biotechnological production from bacteria rich in this acid, and such hyaluronic acid is COSMOS compliant. It is a white powdery substance, very loose. It is added in very small quantities to cosmetic products because it gives very thick gels. The usual concentration is 0.01-0.2%. We will not use it much in gels, but we will learn how to use it in emulsion systems.
Hyaluronic acid molecules are large, with an average molecular weight of 1-2.2 MDa (mega daltons, Mr=1,000,000-2,200,000). The French company Soliance created partially hydrolyzed (cleaved) molecules. Interestingly, by cleaving the molecule, different biological properties are obtained in cosmetics. Primalhyal 300 (INCI: Hydrolized hyaluronic acid) is a hyaluronic acid molecule cleaved into fragments of 100-300 kDa (Mr=100,000-300,000). Its function is to raise the production of natural defence substances, beta-defensin, in the keratinocytes of the skin. It is used not as a gel but as an active cosmetic raw material for skin prone to irritation and infections, atopy and mature skin. Cleavage to even lower molecular weights (25 – 50 kDa, Mr=25,000-50,000) produces Primalhyal 50 (INCI: Hydrolized hyaluronic acid). It stimulates the synthesis of “tight junction” protein of the skin, i.e. it strengthena the structure of the skin. It is used as an active “anti-age” supplement, but also for dry and thinned skin.
Soligel (INCI: Rhizobian gum)
Soligel is a relatively new, biotechnological gel compliant with COSMOS regulations. It is obtained biotechnologically from rhizobia bacteria, species that are symbiotes with some plants such as legumes (Fabacea). In addition to fixing nitrogen from the air and thus replenishing the soil, they retain moisture in special root nodules thanks to this gel. The species from which Soligel is obtained is isolated from sunflower roots. Soligel is not a stand-alone gel: it is low in viscosity and is added as an active and sensory raw material. It gives moisture and softness to the skin, but also improves lubricity and is a real “soft-touch” gel.
It is typically used 0.2-0.3% in other gels and emulsion systems.
Collagen (INCI: Collagen and Hydrolized collagen)
Collagen is another highly marketed molecule from nature. Collagen has many types, and they are a basic component of connective tissues. Like hyaluronic acid, collagen does not enter into the skin, so its use is a bit questionable. Collagen builds a thick gel in water, but it depends on acidity (pH). It is my opinion that it is better to stimulate the synthesis of your own collagen, and applying it from the outside is quite pointless. By the way, collagen synthesis requires vitamin C, so this is another reminder of how healthy food greatly affects our skin. You wouldn’t believe, the finest collagen is obtained from a rat’s tail. This sounds like a witch’s kitchen, but it really is. You may also remember this when buying a collagen cream. In addition to this species, collagen is obtained from other, “butcher” species such as pigs and cows. Therefore, it is not COSMOS compatible at all, and all vegans avoid it. A good reminder for the once widespread collagen injections- after all, these are molecules that are not identical to human ones and against which an immune reaction can occur.
Chondrus crispus gel (INCI: Carrageenan)
The alga Chondrus crispus belongs to the group Rhodophyta, just like the previously described alga, but carrageenans are isolated from many species of algae from the family Gigartinaceae and Solieriaceae. It also contains carrageenans, in fact, it is the main industrial source of these gels. It is used like other gels in a number of products, which includes emulsion systems. The main interest in cosmetics is hair care, making hair gel treatments and shampoos because it gives the hair smoothness.
It can be purchased as a ready-made gel such as red algae gel, and is used in concentrations of 5-50%.
Other minor herbal gels
Agar-agar has long since surpassed its classic use in microbiology- planting bacteria on agar is already a common term in everyday speech. A popular food supplement, especially for healthy cakes, jams and puddings that don’t make you fat because we can’t digest agar. It is obtained from several genera of algae, Gelidium, Gracilaria, Gelidiella and Pterocladia. It is pleasant for the skin, but requires cooking and does not swell in cold water, and is rarely used in cosmetics.
Pectin is a popular gel for cooking marmalades and sweets. It is obtained from the genus Citrus, and is chemically polyuronic acid. Forms gels well by cooking. It is rarely used in cosmetics, but can end up in shower gels.
Sterculia gels derived from the genera of the same name, Ghatti gum (Anogeissus latifolia (DC.) Wallich., Combretaceae, konyaku (Amorphophallus konjac K.Koch, Aracaceae), honey locust gum (Gleditsia sp. Caesalpinaceae) and tara gum (Caesalpinia spinosa (Molina) Kuntze, Caesalpinaceae) are sporadically and rarely used in cosmetics.
Semi-synthetic and synthetic gels
Semi-natural cellulose derivative gels
They are one of the most widely used gels in the pharmaceutical industry, from skin-applied drugs (gels, emulsions) to tablets, capsule fillers and similar products. There are even capsules made from such gels (hydroxypropyl-cellulose capsules). Cellulose itself is one of the most common molecules in the plant world, it is obtained from wood pulp, but also from plants such as cotton. You all know that cotton wool is cellulose. Chemical processing of cellulose, most often the process of formation of ethers and esters, also produces various commercial substances: methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose and the like. Their advantage is that they do not need, most often, the addition of alkali or other substances to thicken them. Although widely used in pharmacy, we will not use them too much because we have other more interesting combinations, and I want to give focus to natural gels. Some, not all, have the disadvantage of peeling easily from the skin. I will only describe the process of obtaining a methyl cellulose gel.
Carbomeric (carbopol) gels (INCI: Carbomer)
Probably the most widely used gels in cosmetics. They are polymers of acrylic, molecules very often used for synthesis. Their preparation is a little more complicated. Swelling of most carbopoles produces rare and acidic gels of low viscosity. Only after neutralization (alkalisation) they boceme thick and transparent gels. It is this process of neutralization that has “brought” into cosmetics unwanted substances, which are avoided in natural cosmetics, and which have brought this group of gels into disrepute. These substances, organic bases, are called triethanol-amine (TEA) and diethanol-amine (DEA). You will find hundreds of warnings on the Internet, some too bombastic, but the fact is that these substances are metabolized into compounds called nitroso-amines which are carcinogenic. The cosmetics industry uses these compounds because they are easier to use than other compounds. Even today, you can find natural cosmetics that contain TEA and DEA. Instead of these two compounds, we will use (and it used industrially, too) sodium hydroxide. It is also dangerous, but when neutralized (merged) with carbopol, it becomes an ordinary, harmless salt. We will talk about this in more detail when we talk about the making of carbopol gels.
Furthermore, another important remark. There are several commercial types of carbopol that differ in viscosity and method of production. Examples are Carbomer 910, 934, 940, 941… One of the most viscous- carbomer 940 is often used. The objection to these types of carbomers is the use of benzene as a solvent in their industrial production. Benzene is an organic solvent that is not harmful in itself, but is metabolized by the body (just like TEA and DEA) into dangerous molecules that are carcinogenic. The question is, then why are they used at all? The reason for this is that there is very little benzene (<0.5%) in the final product (this is also required by regulatory agencies). This should, given the amount of gel in the product, be a “safe” limit. However, we will avoid this type, of which the most common type is 940.
I do not have to emphasize that many manufacturers also use “benzene” carbopoles and TEA and DEA, which is certainly not the best option for the skin. There are of course other types, safer. Carbomer (carbopol) 980 is not produced in benzene, but in completely harmless solvents (ethyl acetate and cyclohexane). It is definitely safe to use, and with proper production without TEA and DEA this is certainly a better solution. It is in this example that we can learn how important it is to know each raw material well and assess what the lowest risk will be for cosmetic use, especially when we also use synthetic substances.
The first reason for using carbopol gels is their superior skin feeling, i.e. incredible lubricity, lightness and skin sensation. Why is that so? Here’s a little secret. Let’s say you plan to sabotage a cosmetics industry for terrorist reasons known only to you. Very simple- when they make carbopol gel, throw in their huge mixers, which work a few hundred kilograms to a ton of this gel, a few boxes of ordinary table salt. And you ruined everything for them. Namely, even lower salt concentrations completely destroy the gel structure of most carbopol and turn it into an ordinary thin slurry. This is seemingly a disadvantage, but also a warning to you if you’re thinking of making a skin gel from sea water. But it is also an advantage. When you apply the gel to the skin, the salt you normally have on the surface of the skin (excreted only by discrete sweating) begins to destroy the structure of the gel, so it seems to disappear and be absorbed immediately – and this is a very desirable phenomenon. Honestly, this reason, along with the next one I’ll cite, is the reason I’m mentioning this gel at all. Carbopol is superior in creating pseudoemulsions, i.e. the ability to disperse oil particles in the aqueous phase, making something similar to a cream. Of course, this is not a perfect emulsion (they are best achieved with both emulsifiers and gel), but it is quite good to have that option.
Beta-gel (INCI: Glyceryl/betaine polyacrylate (and glycerin))
It is the market name for an acrylic-betaine synthetic gel, already mixed with glycerol. Because it is found, similar to algae gel, in a ready-to-dilute form, it is quite popular although it is synthetic. Its name is inconvenient, because there is another gel of the same name made of silicone, which serves to absorb shocks- an egg thrown from a height of 22 meters on a thin layer of beta gel does not break at all. This gel ends up in sneakers with “pads” for absorbing shock when running. Completely useless information for cosmetics, but useful if someone will be confused whether you made the gel from an extract from modern sneakers. Beta gel (cosmetic) is very viscous, thick- 20-30% is added to hydrolate or water, and a very homogeneous and fairly firm gel is formed. If added to emulsion systems as a stabilizer, less is added, about 5-10%, depending on the formulations. Like carbopol gel, it is pleasant for the skin, it spreads easily and does not create a “mask”.