The medicine maker’s stockroom is a beautiful thing – a space (however large or small) replete with healing herbs and the means to extract, administer, and create plant medicines of all varieties. Often nestled in the kitchen, one’s space may host bottled oils of gold and chartreuse, amber-toned jars of honey, infused vinegars in the vibrant hues of the plants they’ve extracted, alcohols ready for the plant witchery of tincture-making, and of course the plants themselves. Found in these charming and powerful spaces somewhat less often, crystal-clear glycerin is a marvelous and multifaceted addition to any medicine maker’s pantry. Glycerin’s history of use reveals it as a versatile ally and a significant agent of change.

What the Heck is Glycerin?

Glycerin is the sweet-tasting component of fats and oils. It is chemically related to alcohol and is also known as glycerol or glyceric alcohol. Though glycerin is sweet, it does not spike blood sugar levels in healthy individuals. Glycerin is processed through different metabolic pathways than sugar (liver vs. pancreas), but diabetics should still use caution.

Glycerin = Fats – Fatty acids. Glycerin can be sourced from any type of fat, though soybeans, palm, and coconut are the most common sources of finished vegetable glycerin. Other sources include tallow and petroleum. Discovered in the late 18th century, glycerin came to be used in medicine and pharmacy over the span of the following hundred years. Glycerin has traditionally been a byproduct of soap and candle manufacture via saponification. The substance is also created when steam pressure and agitation break down fats through the process of fractionation or hydrolysis. Glycerin is produced in massive quantities as a byproduct of the biofuel industry; however, the purification of crude glycerin is involved and costly – this is why glycerin remains a relatively expensive fluid. Crude glycerin is treated with activated carbon, alkali, and ion exchange.  On a much smaller scale, our bodies process glycerin through digestion every time that we eat fats. It is present in the human body as a result.

A Multitude of Uses

Glycerin is used in medicine and pharmacy in the creation of herbal extracts – both as an alternative to alcohol and in addition to alcohol. The details of creating glycerites are explored later in this essay. Glycerin can also be added to syrups and elixirs, either in place of other sweeteners or supplementally. Unlike honey and sugar, it will not ferment which leads to extended shelf life. Glycerin can be combined with herbal extracts and gelatin to make boluses and suppositories for vaginal health concerns, hemorrhoids, and prostate issues. Suppositories and boluses can also be used to deliver medicines that are less localized, as the membranes of the rectum and vagina provide rapid bloodstream uptake via mucous membranes. Glycerin is used as a tablet holding agent in pharmacy, and to preserve cell specimens prior to freezing in laboratory settings – red blood cells are treated in this fashion before freezing for blood banks.

My own introduction to glycerin was as an ingredient in body care products – I have worked in natural products retail for my entire adult life, and one of my favorite jobs therein was that of Body Care Specialist – buying cosmetic and skin care products from suppliers for retail and educating myself and others on their uses and benefits. Glycerin’s emollient, humectant, lubricant, and preservative properties make it an excellent addition to a wide array of topical applications. Glycerin soap can be beneficial to dry and irritated skin – it pulls moisture up through skin’s layers and reduces excessive drying. Glycerin can be luxuriously paired with hydrosols for moisture spray. It is also used in hair gels and conditioners to support texture and sheen. There has been some controversy over the inclusion of glycerin in oral care preparations (toothpaste, mouthwash, etc.). The idea has been presented that glycerin coats the teeth and prevents them from remineralizing. However,  there is no research or basis in chemistry or biology to back this notion. Glycerin is highly soluble in water, so it stands to reason that if it were left on teeth from a toothpaste, it would readily dissolve in saliva. Moreover, glycerin has bacteriostatic action, which could be beneficial to oral health.

Glycerin is about 60% as sweet as sucrose and is processed by different pathways. It has similar caloric density, but a lower glycemic index and does not feed bacteria or candida.

Glycerin is used in food as a humectant, solvent, sweetener, and preservative. It serves as a filler in commercial low-fat foods, a thickening agent in liqueurs, and in the baker’s kitchen can be used to improve the consistency of frosting. Some of my favorite applications of glycerin are culinary. Herbal glycerin extracts prepared from herbs that are particularly aromatic or flavorful make lovely additions to cocktails and mocktails. They can also add an herbal touch of genius to confections when swirled into a batter or the frosting mentioned above.

Glycerin can be used in crafting to preserve flowers in a lifelike manner and is utilized in the film industry to alter the quality of smoke and to enhance and prolong the appearance of water on camera (raindrops, etc.). Glycerin is an ingredient in many E-cigarette liquids (or “vape juices”). It was once widely used in antifreeze because glycerin freezes at -36ºF. It was replaced commercially with ethylene glycol (which has a lower freeze temp) but is under reinvestigation for this purpose as it is nontoxic and better for the environment. In the world of machinery, glycerin is used in lubrication and vibration dampening. Perhaps in most significant opposition to its use in herbalism, glycerin is used in the production of nitroglycerin for explosives, though oddly, nitroglycerin has medicine of its own.

With a Bang

Ascanio Sobrero first synthesized nitroglycerin in 1847 by the addition of sulfuric and nitric acids. It was the first practical explosive developed that was stronger than gunpowder. Sobrero called it “pyroglycerin” and warned against its use as an explosive as highly dangerous. He was so strongly against its use that he told no one of his discovery for over a year. Nevertheless, the explosive power of nitroglycerin would become instrumental to destruction, industrial development, and even medicine in the decades that followed. Swedish chemist Alfred Nobel developed and patented methods for the substance to be more safely used and handled after the death of his younger brother in a factory explosion. These developments included Blasting Oil, Dynamite (which Nobel first wanted to call “Nobel’s Safety Powder”) Ballistite, and Gelignite, among others. The buildings of Nobel’s own factory were destroyed multiple times by explosion in the process.

Nitroglycerin was required for the First Transcontinental Railroad in North America but had to be manufactured on site, as its transport was widely banned after an explosion of liquid nitroglycerin in transit caused the death of 15 and the destruction of a Wells Fargo office. Dynamite was developed in 1867 when Nobel combined nitroglycerin with diatomaceous earth, making use of nitroglycerin safer than it was previously.

During World War II, there was a government initiative for the salvage and donation of cooking fat from households to support the production of glycerin to be converted to explosives for the war effort. Posters urged participation with such bold lines as “Stop! There’s Dynamite In That Grease!” and “Pass the Ammunition!” and “Housewives! Save Waste Fats for Explosives!” Waste fats were returned by the pound to the local butcher and later collected and converted to glycerin for a variety of wartime uses, including the production of explosives.

While nitroglycerin is most widely known as an explosive compound, it is also used as medicine. Glyceryl trinitrate, also called Trinitrin is diluted nitroglycerin. Its use was pioneered by physician William Murrell, and it has been used medically since 1878 for the relief of chest pain or discomfort due to coronary heart disease – ironically, Alfred Nobel was prescribed the medication later in his life, after having developed various delivery methods for nitroglycerin as an agent of destruction.

Herbal Glycerin Extracts

Back to the herbal medicine maker’s stock room, and the medicines we make and dispense as green folk – how can herbalists and their communities benefit from the inclusion of glycerin in medicine making? Glycerin is used as an alternative to alcohol when creating herbal extracts for populations avoiding alcohol consumption, and the substance has a range of advantages in extraction. Sweetness makes remedies much more palatable for children and for folks who dislike the taste of herbal tinctures. Glycerin preserves the juices of fresh plants, a rather unique benefit among solvents used in extraction. It is a stronger solvent and preservative than water, wine, or vinegar (though admittedly, each menstruum has different affinities in extracting various plant constituents). Glycerin blends readily with water and alcohol and is a suitable solvent for tannins – herbs high in tannins benefit from extraction in glycerin or the addition of glycerin to finished alcohol tincture (discussed in later passages).

Glycerin also presents some challenges as a medium of extraction. Alcohol is stronger as a solvent and preservative; by comparison, glycerin produces less potent extracts with shorter shelf lives. Glycerin is also more expensive than alcohol. Heat increases glycerin’s level of solvency, so preparing extracts with the application of heat will yield a more potent finished product. In general, glycerites will remain stable for a minimum of three years, as long as they contain enough glycerin. If alcohol need not be avoided entirely, 22% grain alcohol may be used to further preserve a glycerite and for greater cost efficiency. Glycerin will not extract mucilage or resins – alcohol and oil are better solvents for resins, while water is best for mucilage. Glycerin mixes readily with water and with alcohol but does not blend with oil.

My first glycerite was made in the company of my two greatest herbal partners-in-crime. We had studied herbs together in a year-long program and would later work together at a local apothecary, all of which we enjoyed immensely. For all of the medicine making we had done in our formal studies, somehow the glycerite had evaded our curriculum. We endeavored to create a dry Ginger root (Zingiber officinale) glycerite, taking the bulk of our instruction from Richo Cech’s Making Plant Medicine, though probably not following the directions to the best of our benefit. We macerated the herb in absolute glycerin for weeks (It turned out super hot and spicy – in hindsight, fresh ginger would have been much more practical and delicious, or we could have diluted our menstruum by about 40% – but that’s what first tries are for). I would later prepare Lemon Balm (Melissa officinalis) glycerite for a dear friend in need who was abstaining from alcohol and teach students to craft glycerites my own medicine making intensives.

Richo Cech, James Green, and Thomas Easley and Stephen Horne provide excellent in-depth direction in their works (cited at the end of this essay), and I am immensely grateful for the knowledge I have gained from the books they have written. Below are the tips and methods I have found most useful and practical.

When preparing a glycerite, there are a few things to note. Firstly, pure glycerin readily pulls moisture from the air, and so is 95% pure, with 5% water by volume. Vegetable glycerin intended for consumption is recommended for making herbal extracts. The finished product should be stored in airtight, light-resistant containers away from sunlight and excessive heat. Refrigeration is not necessary but may extend shelf life. 

Dry plant preparations should be crafted with a 55-60% glycerin, while fresh plants require 80-90% glycerin. This is because there is water present in the plant, which will be released in the extraction process. Like alcohol-based extracts, dry plant extracts are generally made with a plant to menstruum ratio of 1:5, fresh plant extracts with a ratio of 1:2. 

The following rules can be applied to dry plant glycerites: When using 1 ounce (by weight) of an herb, you will use 5 total ounces (liquid measure) of glycerin/ water combination to create your extract. To achieve 60% glycerin in this example, one would combine 3 ounces of glycerin with 2 ounces of water (3 oz. glycerin + 2 oz. water = 5 oz total menstruum: 1 oz. dry herb). When using a different amount of herb, simply multiply each liquid measurement by the number of ounces of herb used. 

The following rules can be applied to fresh plant glycerites: When using 1 ounce (by weight) of an herb, you will use 2 total ounces (liquid measure) of glycerin/ water combination to create your extract. If your plant material is particularly juicy, use undiluted glycerine, as the plant’s juices are likely to dilute the final product. If you’re using a plant that is less juicy, for every one ounce of plant material (by weight), roughly 1.8 oz glycerin and 0.2 oz water will form a suitable menstruum (1.8 oz. glycerin + 0.2 oz water = 2 oz. total menstruum: 1 oz. fresh herb). 

If weight-to-volume makes your head spin, or it’s just not your style, you can choose to instead cover your plant material by at least 1/4 of an inch. Sometimes this is necessary to ensure that there is adequate menstruum if the plant material is particularly light and voluminous. Use undiluted glycerin for fresh plants and dilute using the example above for dry.

The following plants are well extracted in glycerin, owing to the presence of tannins or volatile juices: Burdock (Arctium lappa), Chamomile (Matricaria recutita), Cleavers (Galium aparine), Dandelion (Taraxacum officinale), Elder (Sambucus nigra), Eleuthero (Eleutherococcus senticosus), Fennel (Foeniculum vulgare), Ginger (Zingiber officinale), Goldenseal (Hydrastis canadensis), Hawthorn (Crataegus spp.), Mugwort (Artemisia vulgaris), Mullein (Verbascum thapsus), Nettle (Urtica dioica), Oat (Avena sativa), Peppermint (Mentha piperita) and other aromatic members of the mint family, Rose (Rosa spp.), Skullcap (Scutellaria lateriflora), Uva ursi (Arctostaphylos uva-ursi), Vitex (Vitex agnus-castus), and Valerian (Valeriana officinalis).

Methods of Crafting a Glycerite

Dry Maceration

This is perhaps the simplest and most straightforward method of creating a glycerite. Macerate powdered dry herb for 14 days in 55% glycerin (45% water), covered by 1/4 in. Strain, cool, and bottle.

Traditional Method

Also extremely user-friendly: create a strong infusion (for light, leafy material) or decoction (for dense materials such as barks, berries, and roots) of the herb. Add 60% glycerin; strain, cool, and bottle.

Standard Method

Combine dried herb with 55% glycerin and 45% water. Simmer for 20-30 minutes, strain, cool and bottle.

Fresh Plant

Stuff a mason jar with your fresh plant, leaving 1 inch of headspace. Add a menstruum of 80% glycerin, 20% water. Close the jar, and allow 15 minutes in a boiling water bath. Cool, strain, and bottle.

Glycerites can be taken at twice the dose of a similar alcohol-based extract. I enjoy using them as a base for custom flower essence blends, a sweet application that I learned at the apothecary where I used to work – rose and lavender are particular favorites for this use. 

Glycerin in Alcohol-based Tinctures

Glycerin sometimes appears as an ingredient in alcohol-based tinctures. In some cases glycerin is added to make an extract more palatable; however, the addition of glycerin to some plant extracts confers additional benefits. Glycerin amends the relationship between alkaloids and tannins; it prevents alkaloids from being precipitated in the presence of tannins. Tannins are large plant molecules that bind readily with proteins, cellulose, starches, and minerals. These resulting substances are insoluble and resistant to decomposition – they are part of a plant’s system of defense. Though tannins have medicinal benefits of their own (they are astringent and have been shown to prevent bacterial adhesion), their chemistry can cause some challenges in making medicine. When tannins bind with other plant substances, the insoluble solids that they create are called precipitates. In tinctures, these can be observed as sediment that has fallen out of suspension.

Aside from the aesthetic desire for a well-suspended, clear tincture, avoiding precipitates can be a matter of safety. Some medicinal plants contain powerful alkaloids that command moderation. If these alkaloids are precipitated by the presence of tannins, the majority of an extract’s alkaloids may be ingested in high concentration in the final doses. Shaking bottled extracts before each dose is one fix, but 5-10% glycerin in the menstruum provides a well-suspended extract with greater clarity.

The following herbs benefit from the addition of glycerin to avoid precipitates when prepared as alcohol-based tinctures: Alumroot (Heuchera spp.), Bistort Root (Polygonum bistorta), Cinnamon (Cinnamomum verum), Cranesbill (Geranium spp.), Guarana (Paullinia cupana), Rhatany (Krameria spp.), Rhubarb (Rheum rhabarbarum), Sweet Sumach (Rhus aromatica), White Oak Bark (Quercus alba), and Wild Cherry (Prunus spp.).

Glycerin makes many plant medicines more accessible and convenient to those avoiding alcohol, and more palatable for children and folks who don’t enjoy tinctures. It can make plant extracts more safe, aesthetically pleasing, and effective. It is a complex substance with a fascinating (sometimes sweet, sometimes volatile) history. An admirable emollient, solvent, preservative, and sweetener, glycerin is a lovely addition to any medicine maker’s pantry.

References

Cech, Richo. Making Plant Medicine.

Easley, Thomas. and Stephen Horne. The Modern Herbal Dispensatory.

Green, James. The Herbal Medicine Maker’s Handbook.

Moore, Michael. Herbal Materia Medica: Fifth Edition.