Shaving alum is a common ingredient used in post shaving routines and for shaving nicks and weepers.  Today we are going to go over what alum is, what it’s good for, and clear up some confusion regarding it’s use.

When wet shavers start to talk about alum most think of an alum block and some version of a styptic pencil.  I thought the same thing, and found out I was only partially correct as I was researching this article.  Alum blocks ARE made from alum, but it appears that modern day shaving styptics are no longer exclusively formulated with an alum component.

Read on to find out more.

Alum blocks

What is shaving alum?

First of all, the name alum is in itself misleading.  Doing a little research shows that there are 6 or so substances that can be classified as an alum.  In wet shaving, alum usually refers to “Potassium Alum (also known as Potassium Aluminum Sulfate or Potash Alum).    While similar, each has a distinct and separate composition.

Types of alum seen in the shaving world

Potassium alum or shaving alumPotassium alum (Potash alum):

Aluminum potassium sulfate is the most common form of alum used in wet shaving products.  It is used as an astringent and antiseptic in various food preparation processes such as pickling and fermentation and as a flocculant for water purification, among other things.  This is a naturally occurring mineral that is mined and often sold as Alum blocks for shaving and deodorants (check the ingredients on the examples here 1, 2, 3).

These alum blocks are used after shaving to help close any weepers and “clean” the skin to lessen the chances of infection.  This is often helpful for those who suffer from acne and/or ingrown hairs.  Alum blocks are also often used as an underarm deodorant because of its antimicrobial properties.  Alum can have a drying effect on skin and can be a mild irritant.

Aluminum sulfate:

Aluminum sulfate is also used in wet shaving products, but not to the extent of Potassium alum.  It is soluble in water and is mainly used as a flocculating agent in the purification of drinking water and wastewater treatment plants, and also in paper manufacturing.

Other forms of alum are Soda alum, Chrome alum, Selenate-containing alums, and Ammonium alum

How to use an alum block

While this doesn’t really need its own paragraph… I figured why not cover all of the bases.  Alum usually is sold as small blocks of clear/whitish stone that are wrapped in plastic.  Some of the better products actually come in a little plastic case to keep it safe.  Be careful when handling your alum block.  If dropped it has a VERY good chance of shattering.  While you can use the resulting shards, it’s probably better to spend another couple dollars and buy a new one.  Prices run from $6 to $20 and largely depend on the size of the alum block and the name brand on the label.

Alum blocks are used as a post shave treatment and as a deodorant.  After your shave splash some water on your face and get the alum block wet.  Rub the block along your face where you shave.  This will help close any weepers, kill bacteria, and tighten up your skin a touch.  Most people will clean up thier shave gear or something similar and then was off thier face.  You can leave it on but it can be a mild skin irritant.  Try not to let the water get onto your lips as it tastes horrible.  As far as deodorant use goes, just wet the block and rub it around in your armpits.  It will not prevent wetness, but will kill any odor causing bacteria and will not leave any whitish marks on clothing.

Misconceptions / Safety information about alum

Toxicity Fears

Alum is approved by the U.S. Food and Drug Administration as a food additive.  However,  in quantities over an ounce it is toxic to humans.  If you don’t mistake it for a sucker or a cough drop you should be fine.  Since it tastes terrible this shouldn’t be an issue…

Aluminum Fears

The various forms of alum are an Aluminum “Salt”.  This has caused people to be worried about absorbing aluminum through thier skin because they think it’s bad for them.  People believe that aluminum causes or contributes to Alzheimer’s disease and/or can cause cancer.  Most of this concern started because of a study about elevated levels of aluminum found in the brain plaque of a small group of test subjects who were afflicted with Alzheimer’s disease.

This caused a lot of fear and confusion among the general populace.  While the rumor/belief will never completely go away, the current medical belief is that the elevated levels were not causally related to the Alzheimer’s.  If you are still concerned please see the links below.  As a personal note…. imagine how much alum block you are going to have to use to absorb enough to even register on a laboratory test let alone affect bodily functions.

Shaving Styptics

classic styptic pencil shaving alum whyiwetshave.comA shaving styptic is used to stop the flow of blood from by causing either the blood to coagulate faster and/or the cause the wound (and especially the capillaries that were damaged) to constrict, thereby stopping or slowing the loss of blood (this is also discussed in How to stop a razor cut from bleeding).  Styptics can come in a solid, powder, or liquid form.

While looking at styptics you will see that the old fashioned styptic pencils seem to be make up primarily of Aluminum sulfate and some kind of binder material.  Modern liquid styptics use mixtures of Aluminum Chloride, Benzalkonium Chloride and Zinc Chloride.  Powdered styptics seem to use Ferric subsulfate or Aluminum sulfate (one of the common forms of alum).

How to use a styptic

Using a solid styptic pencil

Rinse and dry the bleeding area first.  Take the styptic pencil and very slightly get it wet.  Rub the damp end of the styptic pencil on the cut.  It WILL sting, but that just means you have gotten it where it needs to go.  You can apply a bit of pressure to the wound with the styptic if needed as well.  When the wound stops bleeding you will often have a black clotted mass at the wound and some whitish residue around the wound.  You can carefully wipe off the whitish residue, but do not disturb the black crust.  Dry the styptic pencil off and place it in a dry area for storage.

Using a powdered styptic

Rinse and dry the bleeding area first.  Apply a dab of styptic powder on your finger or a q-tip and use that to apply the powder to the wound.  This will cause a pronounced stinging sensation.  When the wound stops bleeding you will often have a black crust at the wound and some styptic residue around the wound.  You can carefully wipe off the residue, but do not disturb the black crust

Using a liquid styptic

Rinse and dry the wound area.  Some liquid styptics have a roll on applicator, while others come in something resembling an eye dropper.  Apply to wound site and let dry.  Most liquid styptics provide a protective barrier as well stopping the bleeding.


Hopefully you are a little wiser about how shaving alum fits into wet shaving.  I am personally a big fan of alum blocks but prefer to try direct pressure and tissue rather than a styptic for cuts..  I just don’t like the mess involved.  Links to more information are provided below.

Have a great day and a smooth shave!


Potassium alum-wikipedia

Ammonium aluminium sulfate – wikipedia