Alum stone user's guide

From the Latin alumen, meaning "bitter salt", alum stone was already mentioned in the famous work of Dioscorides, De Materia Medica. It has been used since antiquity for its many properties, the main one being its astringent power. Tightening the pores, it is a real natural ally in daily life to limit perspiration and reduce the dilation of pores in problem skins. It also facilitates the healing of small wounds related to acne or hair removal and shaving. Denigrated these last years because of the evoked dangers of the salts of aluminium in the deodorants, we say all to you on this surprising stone.

What is alum stone?

Alum stone is in fact a crystal extracted from a mineral called alunite or bauxite. At the time, the latter came from Syrian quarries but nowadays it is found in mines, surface outcrops or volcanic soils all over the world. This mineral is a double sulfate of aluminum and potassium. In natural cosmetics, alum stone is used for various benefits. First of all for its astringent character which means that it tightens the pores of the skin. This characteristic allows it to regulate perspiration and to be used as an anti-perspirant and natural deodorant but it also reduces the deposit of sebum in oily skin. Thanks to this property, the stone also facilitates healing, it is often used following depilation or shaving to stop micro-bleeding and soothe the skin.

You can find alum stone in two forms:

  • In block: The potassium alum crystals, once purified, are recrystallized in block or stick form and used directly on the skin.
  • In powder: The crystals are then in this case crushed in very fine powder which is going to be incorporated in your cosmetic preparations house for the same properties.

How to use alum stone?

In cosmetics

To enjoy the benefits of natural alum stone, simply moisten it with water before use. Then pass it on a dry and healthy skin. Depending on the properties you are looking for, you can use it in combination with essential oils or floral waters to optimize its benefits. Here are some ideas:

  • Natural deodorant

Using alum stone with hydrolats or essential oils allows you to effectively regulate perspiration and limit the small inconveniences associated with it.

- Essential oils : Rose Geranium, Fine Lavender, Palmarosa, Clary Sage, Peppermint, Cypress of Provence. Add on your stone a drop of essential oil with antibacterial properties and pleasant scent to act in addition on the odors of perspiration.

- Hydrolats : Peppermint, Clary Sage. Moisten your stone with these hydrosols to regulate the hormones responsible for sweating and provide a refreshing sensation.

  • Oily and acne-prone skin.

In view of its astringent and consequently matifying character, the stone of alum is appreciated by the fatty and acneic skins to tighten the dilated pores collecting the sebum.

- Essential oils: Tea Tree, Rose Geranium, Petit grain de Bigarade, Fine Lavender. Add a drop of essential oil with purifying and anti-inflammatory properties on your stone to reduce your acne pimples.

- Hydrolats: Peppermint, Rosemary Verbenone, Hamamelis, Cistus, Tea Tree. Moisten your stone with these hydrolats to reduce shine in certain areas of your face.

  • Healing

The astringent property of the stone of alum also allows him to accelerate the process of cicatrization, even more with the essential oils and adapted hydrolats.

- Essential oils: Italian Helichrysum, True Lavender, Rose Geranium. Add a drop of healing and purifying essential oil on your stone to regenerate skin cells and reduce scars.

- Hydrolats: Rose Geranium, Italian Helichrysum, Yarrow, Cistus. Moisten your stone with these hydrolats to complete the healing action in damaged skin.

Technical data sheet of the alum stone

Main properties

Astringent: Alum stone is an astringent mineral, which means that it will be able to tighten the pores of the skin. It is by this property that it allows to limit the perspiration in a natural way. It is also an ally of the fatty and acneic skins with dilated pores.

Healing: Alum stone therefore has, thanks to its astringency, the ability to accelerate the healing process with the help of the thin mineral layer deposited on the skin's surface.

Hemostatic: Alum stone helps stop micro bleeding that can occur especially after micro cuts from hair removal or shaving.

Technical specifications

Biochemical characteristics

A good natural alum stone should contain (in %)

  • SO3: 34%.
  • Al2O3: 11%.
  • K2O : 10
  • H2O: 45% OF THE TOTAL
Physical characteristics

A good natural alum stone should have the following physical characteristics:

  • Density at 20°C: 1.75
  • pH : 3,5 (+/- 0,5)
  • Melting point : + 92° C
Organoleptic characteristics

What a good natural alum stone looks like:

  • Appearance: crystal block or fine powder
  • Color: translucent, whitish
  • Odor: odorless

Precautions of use of the stone of alum

Authorized use of the product

Authorized users


Do not use on injured skin. Avoid contact with mucous membranes.

Storage and preservation

Let dry after use. Store away from moisture, light and heat.

Does alum stone present any dangers?


Aluminum is one of the most abundant natural elements in the earth's crust and at very high doses in the bloodstream can be dangerous for human health. Recently, aluminum salts have been singled out for their increased presence in consumer products: water, food, drugs and cosmetics. Like other chemical compounds, they are believed to have an impact on the development of various neurological and cancerous pathologies.

Within cosmetic products, it is more precisely the aluminum chlorohydrates mostly found in commercial deodorants and antiperspirants that are blamed for their carcinogenic character. They would facilitate the passage of aluminum through the skin into the body. However, no official study has determined whether or not aluminum passes through the skin. The French National Agency for the Safety of Medicines and Health Products (formerly Afssaps) has evaluated the risks to which cosmetic consumers are exposed when faced with different types of aluminum salts. This study did not show a link between aluminum and cancer, but as a precaution, it was still decided to restrict the amount of aluminum to 0.6% in cosmetic products. It is also discouraged to use aluminum-containing products on injured skin to avoid any passage into the bloodstream.

Natural Alum Stone does not contain aluminum chlorohydrates and no official comments, studies or facts have concluded any toxicity from it under reasonable conditions of use.

Natural stone VS Synthetic stone

And yes, you must be careful when you get alum stone because there is a natural and a synthetic one. They differ in their manufacturing processes and chemical composition.
The natural stone is therefore alum potassium extracted from alunite which will be purified and then recrystallized by natural methods lasting about 6 months. The synthetic alum stone, on the other hand, is obtained by heavy polluting chemical processes. It is composed of alum ammonium(NH4)Al(SO4)2 from residues and ammonium salts, the majority of which comes from the nylon industry in Asia. The use of the latter has reported several times in consumers of irritation and inflammation in the armpits. So be careful and once again, choose Mother Nature!

The manufacture of natural alum stone

To make your natural alum stone stick, the extracted alum will undergo four operations:

  • the calcination: This step is carried out over one day and under very high temperature, between 600 and 700°C. It allows the ore to lose all the water in order to obtain an anhydrous sulfate as well as alumina. It is very important to control the temperature during this stage because below 600°C the decomposition of the alunite is incomplete and above 700°C the sulphates are lost but they are necessary for the formation of the stone.
  • the maceration: Then the obtained anhydrous sulfate is rehydrated during the maceration by sprinkling with water to form potassium alum of formula KAl(SO4)2-12H2O. This step is the longest and can last 2 to 4 months maximum until a pasty mass is obtained from which the potassium alum will be extracted.
  • the lixiviation: This operation allows to extract the potassium of alum following the maceration. It consists of a leaching with hot or even boiling water of the mineral paste mass in order to solubilize the alum and remove the impurities which are insoluble. This also aims to concentrate the potassium alum before its crystallization.
  • the crystallization: This is the last step in the manufacture of your stick. The hot solution of potassium alum recovered beforehand is placed in vats within which it will cool down in about two weeks to form crystals. Those placed in the center of the tanks are then recovered to be cut and polished according to the desired shape.
Alum stone in tube French manufacturing

62 notes

See the product