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The Potassium Alum Block: An Essential Shaving Tool You Might be Missing

by Nathan Gareau Last updated: May 20, 2021 0 Comments

What comes to mind when I ask the question, “What tools are essential in your shave kit?”

I’m guessing you probably thought, “A razor, duh Nathan. Have you been huffing aftershave?”

Some of you may have thought of a shaving brush, maybe even a leather strop if you’re a fan of the straight razor! 

While each of these can be absolutely vital, there’s another tool, often overlooked by shavers, that will seriously improve your shave: The humble Potassium Alum Block.

If you shave your face, legs, or anything else, you need an alum block.

What is a Potassium Alum Block?

Potassium alum, simply called ‘alum’ or an ‘alum block’ in the shaving world, is a crystal compound that has been used for centuries across the world. It occurs naturally from evaporating water rich in its component minerals, much like sea salt. Nowadays, it’s produced industrially for convenience and purity. In both the ancient and modern world, it is used for water purification, leather tanning, dyeing, and more, but our application specifically pertains to shaving.

Why do I Need a Potassium Alum Black for Shaving?

Conveniently for us who shave, alum is a potent astringent and antiseptic, both of which you need after shaving. Shaving with any blade can cause tiny abrasions to the skin, most of which you can’t see. If you have sensitive skin, like me, this can cause redness and irritation, but they can also become infected, causing acne. The solution? Alum block. The alum block eliminates bacteria, leaving your skin clean and clear!

Alum also works wonders for visible nicks, the little spots that can show up on sensitive areas, especially if you have fussy skin and shave against the grain. I have the dreaded combo of coarse hair and sensitive skin, and I often get a ton of tiny nicks on my neck that shows up as little red blotches after my shave. Alum constricts the blood vessels and stops the bleeding, cleaning up these little nicks so you can avoid the tissue-paper-on-the-neck look my dad always rocked after his shaves when I was a kid; if only he discovered the alum block sooner.

How to Use a Potassium Alum Block

After your shave:

  1. Rinse your skin well with cold water (hot water dries out your skin).
  2. Wet your alum block under your tap, and rub it across your skin anywhere you’ve shaved. This will disinfect and clean up any micro nicks, preventing acne, irritation, and the dreaded red spots.
  3. Let the alum sit for a couple of minutes; then, pat your face with a damp towel. This removes the excess salty residue from your skin, but make sure you use a clean towel.

Keep in mind that alum is a type of salt, so it’s not for everyone. If you suffer from dry, sensitive skin or if you find the alum irritating your skin, use alum as a spot treatment for nicks, but avoid using it all over.

Always follow alum with an aftershave balm, as your skin will be craving the moisture it provides. Remember to keep your hands clean during this process, and try to avoid touching your face during the day, so you’re not introducing nasty bacteria to your skin. Now enjoy your happy, clear skin!

Another handy use for an alum block is stretching your skin while shaving. Keeping your skin taught is vital for getting the closest, most comfortable shave possible, but it's challenging with fingers that are slippery from shaving cream or preshave. If you're struggling, rub your fingertips on your alum block, then pull. The alum dries out your fingertips enough to give Spiderman-like grip when stretching your skin.

Using Potassium Alum Blocks as a Natural, Zero-Waste Antiperspirant

Alum blocks are also very popular in the world of natural health as an antiperspirant! As I mentioned, the potassium alum inhibits the growth of bacteria, which is what causes body odour. Simply wet the block, rub it onto your underarms (or other sweaty areas) and let it dry. If you’re a sweaty guy like me, you can even layer your regular deodorant over it. I like to take an alum block camping and hiking, as I try to avoid scented products when I’m in the woods.

Styptic pencils are made of aluminum sulfate, pressed into an easy-to-use stick!

What’s a styptic pencil? And what the heck are Styptic matches?

If you shave with a straight razor or are a bit clumsy like I am, you’ll eventually get a cut that requires more than a simple alum block. Don’t worry; your straight razor won’t give you a horror-movie gash, but you can get small cuts that alum blocks simply can’t handle.

Potassium alum tightens blood vessels and slows the flow, while its tougher cousin aluminum sulfate straight up clots the blood and stops bleeding in its tracks. If you ever get an “on no” cut, just wet your styptic pencil and gently press it onto the cut. It feels terrible, but it works like a charm. 

Styptic matches are similar but designed for single use. Since barbers require careful sanitation of their tools between shaves, a disposable alum solution was necessary for fixing the odd accident. Conveniently these matches are super-compact, making them excellent for travel. Just rip one off, wet the tip, and apply it to the wound. If you start cursing, that means it’s working.


Alum blocks, matches, and styptic pencils each have unique uses, so it's handy to have all three!

We’re also pretty big on camping and outdoor activities at Kent of Inglewood, and I find these tools are essential in my campsite first-aid kit. Whenever I nick myself carving a spoon or practicing my bushcraft skills, the styptic pencil does the trick. 

Much like the noble safety razor, my alum block changed the way I shave for the better. It helps me care for my skin and put my best face forward, but its sting is also an excellent reminder to focus while I’m shaving. If you shave any part of your body, you need an alum block, and if you’re an avid shaver like me, you probably need a block, a pencil, and the matches.

Happy shaving!

Grab some alum today!

Nathan Gareau
Nathan Gareau

A famed cocktologist and axe man, Nathan opened the first Kent of Inglewood store in Calgary, and now spends his days writing most of what you are reading here and teaching straight razor shaving classes. Ask him about his world-famous Three Cherry Manhattan. In his spare time Nathan can be found sharpening his axe, making fermented foods, or practicing his amateur butchering hobby. He doesn't slur his words, he speaks in cursive.