Last week we took a look at the structure and production of glycerin, and how this everyday substance is also found in dynamite. Today, we’re talking about its many uses and how different industries utilise the properties of this multi-dimensional liquid.
Glycerin is a sugar-alcohol with the chemical formula C3H8O3. While this is remarkably similar to the structure of isopropyl alcohol, these two compounds couldn’t be any more different. Physically, glycerin is a colourless and non-toxic liquid that is characterised by its sweet taste. Chemically, it is a trihydric alcohol known for its hygroscopicity and solubility in water.
There are over 1,500 known uses for glycerin, ranging from skin care to printer ink to hydraulic fluid. It would be impossible to list of all these, so we’re just going to talk about the top 3.
The trihydric structure of glycerin means that it is miscible with water and extremely hygroscopic. This means that it is not only soluble with water, it is also able to attract water from its surrounding environment. For these reasons, it is commonly used as a humectant, a substance that retains moisture, and an emollient, a substance with softening qualities.
Because it is non-toxic, glycerin can be used on every part of the epidermis, including the mucous membrane. All of these characteristics make glycerin well-suited to a variety of cosmetic applications.
Its humectant and emollient properties make glycerin perfect for hydrating and softening your skin. Therefore, it is commonly found in things like moisturisers and lotions.
Dry skin is caused by a loss of moisture from the outer layer of skin. When applied topically, glycerin-based moisturisers form an oily layer. Its humectant properties then kick into gear as it draws water into the outer layer of the skin. Its capacity as an emollient then enables it to soften the skin’s top layer.
This encourages dead skin cells to fall away, helps skin lock in moisture, and leaves it feeling smoother. The oily layer glycerin forms also helps to keep toxins from entering.
When used in this way, its concentration is usually below 50%. This is because its hygroscopic molecule attracts water at such a high degree that, if pure glycerol was used on skin, it could cause blisters. This is why the cosmetic industry uses diluted glycerin in its products.
Glycerin is not only an excellent moisturiser, it also has range of restorative qualities that make it suitable for a variety of skin care solutions.
Its humectant properties and hygroscopicity means that glycerin is quite effective at repairing and regenerating skin cells. Because of this, it can help to improve cracked heels, eczema and hand dermatitis. Glycerin also reduces the time it takes a wound to heal by 25%, as well as improving the appearance of scars. It can even rebalance the pH of your skin by behaving as a toner.
When our skin secretes sebum from its oil glands, it forms an acid mantle later by mixing with our natural sweat. This layer has a pH that ranges between 4.5 and 5.5, which is the average pH balance of skin. An acid mantle layer on top of our skin may sound unnerving, but it is actually essential for protecting our skin against dirt and toxins.
There are many things we do that can throw off the pH of our skin. For example, using the wrong kind of soap can have a big impact on your complexion. When skin is dry, it means that the pH is above 5.5 and is therefore too alkaline. When skin is inflamed or prone to break outs, it indicates that the pH is below 5.5 and is thus too acidic.
Toners are used to help rebalance the pH of your skin, and glycerin is especially good at this because it is a humectant and emollient. Many facial toners contain glycerin as an ingredient. A testament to its non-toxicity is that glycerin also has a strong presence in infant skin care.
The humectant characteristics and the sweet taste of glycerin gives it a large variety of uses within the food industry where it behaves as a moistening agent, emulsifier, sweetener and preservative.
The sweet taste of glycerin is one of its most recognisable characteristics. In fact, it’s considered to be 60% as sweet as other refined sugars with a lower calorie percentage per teaspoon.
Glycerin is used in the food industry as an artificial sweetener. It is added to ice cream and most processed foods. Most commonly, it’s used in baking, especially in making fondant more pliable and icing more sweet and viscous.
An emulsifier is used in the food industry to prevent the separation of oil and water in a mixture by acting as an intermediary. This helps to create stable and homogenous emulsions that have longer shelf-life. When making bread, for example, emulsifiers are crucial for the bread’s texture, moistness, fluffiness and shelf-life.
From last week’s post, we know that fats are triglycerides that have a glycerin backbone. In nature, rather than having 3 hydroxyl groups, glycerin has 3 fatty acids attached to its structure. In the natural production of glycerin, one of these fatty acids are removed. This allows the glycerin molecule to attach to something else, like water, while the remaining fatty acids attach to other fats.
Therefore, the molecule will now have a hydrophilic end that interacts with water, and a hydrophobic tail that interacts with fat and oil. This is how emulsifying molecules are structured, and shows why glycerin makes a good emulsifier.
Let’s go back to the bread example. Monoglycerides, the glycerol esters of fatty acids, are used as the emulsifier to help stabilise the dough and prevent staling. Emulsifiers also play an important role in the texture of the bread as they interact with gluten to strengthen the protein network. In cakes and pastries, emulsifiers are important because they improve gas bubble stability. This is what creates a light and fluffy end result.
By creating a richer, stabilised formulation, emulsifiers lead to the bread having a longer shelf life. Glycerin’s structure, hygroscopicity and sweet taste make it an ideal emulsifier in this way.
Glycerin’s capacity as an emulsifier is strengthened by its humectant properties, which are what lends bread, pastries and other baked goods their moistness. It also helps to preserve foods by attracting water from the environment, thus reducing the likelihood of staling.
Glycerin is one of the most widely used ingredients in medical prescriptions, second only to water. It has a wide of range of applications in this industry, and is often used to help make prescriptions more palatable.
Cough syrup contains glycerin because of its sweet taste and viscosity. This is why cough syrup is quite thick and sweet tasting. Medicine capsules are also plasticised with glycerin because it is non-toxic and can be consumed. Other pharmaceutical treatments that use glycerin include:
- Glaucoma: glycerin is used to decrease pressure in the eye
- Constipation: the softening qualities of glycerin mean that it is able to ease constipation
- Vasodilator: nitroglycerine, which is also found in dynamite, is used in angina treatments
Cerebral edema happens when there is an excess accumulation of fluid in the intra-cellular spaces of the brain. It usually follows brain trauma, cancer or a stroke.
Because of hygroscopicity, glycerin is used in IV fluids in order to reduce excessive intracranial pressure caused by cerebral edema. It does this by drawing out excess fluid from the body tissue and bloodstream, which it is able to do by being extremely hygroscopic.
It then dehydrates the tissue by preventing the kidneys from reabsorbing water. This reduces the volume of blood which ultimately reduces intracranial pressure.
We have only made a dent on the tip of the iceberg that represents the thousands of uses glycerin has. Other applications include glycerin being included in gums and resins for protective coatings, which have particular use in the automotive industry; in the printing industry where it is used to make ink; in dynamite and projectiles, which we touched on last week; and in automobile radiator cooling systems, where it was the first permanent antifreeze before being replaced with ethylene glycol.
Our online shop is stocked full of glycerin. With a range of batch sizes, next day delivery, and internationally approved quality products, what’s stopping you?
The blog on chemicals.co.uk and everything published on it is provided as an information resource only. The blog, its authors and affiliates accept no responsibility for any accident, injury or damage caused in part or directly from following the information provided on this website. We do not recommend using any chemical without first consulting the Material Safety Data Sheet which can be obtained from the manufacturer and following the safety advice and precautions on the product label. If you are in any doubt about health and safety issues please consult the Health & Safety Executive (HSE).