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8 min read

I still remember a gift a colleague gave me while on a business trip to Hong Kong—an alum block. I didn't know what it was at the time or how to use an alum block, but it proved to be one of the most useful gifts for traditional wet shaving I've ever gotten.

I've since learned that achieving the perfect shave is all in the follow-through. Although it could be easily overlooked, the post-shave routine is just as important as the shave itself, and the alum block is an essential part of that.

What Is An Alum Block?

What is an Alum Block

An Alum Block is a crystal-like stone in the shape of a miniature bar of soap, also known as an alum stone or alum crystal, a mineral block made from potassium alum, a naturally occurring mineral and composite known for its antiseptic and astringent properties.

Historically used by the ancient Egyptians, potassium alum was used more than 4,000 years ago for its antiseptic and healing properties and to cool and revitalize the skin.

Available in different shapes and sizes, such as an alum bar or crystal, there are convenient travel-size alum sticks for precise application.

The alum bar today is utilized as a wet shaving essential in the post-shave process to cool and refresh the skin after shaving wetted with water and gently rubbed over the shaved area to minimize redness and soothe irritation, limit the appearance of razor bumps, fight razor burn, and heal minor nicks and cuts.

Because of their antibacterial properties, alum blocks can even tighten pores, kill surface bacteria, and reduce pimples and acne.

The History Of  The Alum Stone

history of the alum block

It seems to be true that people have almost always sought better therapeutic remedies. In addition to being found at many archaeological sites in Egypt, the mineral block has also been discovered in sites that suggest they were also used in Ancient Greece and Rome.

The original alum block enthusiasts were actually the ancient Egyptians. More than 4,000 years ago, the Egyptians came to discover the antiseptic and healing properties of the mineral. Although our image of the ancient Egyptians might not necessarily align with a concern for a hedonistic pursuit of comfort or vanity, they knew that the alum block felt really good and cooled their face in the heat. That's all it took for the practice to become commonplace.

The Ancient Greek historian Herodotus wrote that Egyptian alum was a valuable commodity back in his day. Similarly, the Ancient Roman historian and army commander Pliny the Elder documented that the Romans used the substance in their medicine and for dyeing fabrics. During the Islamic middle ages, alum was used extensively as a "mordant"—a chemical that helps dyes set into fabrics.

What Is Alum Used For?
The Benefits & Uses of An Alum Block

The benefits and uses of an Alum blockAlum (aluminum potassium sulfate) is mineral block that acts as a natural coagulator, astringent and antiseptic. The alum block is a versatile therapeutic treatment used to eliminate all kinds of undesirable shaving and related skin problems. Such as:
  • Increase grip on slippery safety razors or straight razor handles
  • Treat small nicks and cuts
  • Fight razor burns
  • Improve skin tone
  • Reduce skin inflammation
  • Address post-shaving related skin irritation
  • Reduce the appearance of razor bumps
  • Heal minor bleeding by constricting blood vessels and tightening pores
  • Replace your favorite scented deodorant
  • Clear up pre-existing skin conditions like acne or spotty skin for a better appearance
  • Reduce the risk of developing ingrown hairs
  • Calm the skin and avoid razor bumps for women after waxing sensitive areas

When using an alum block, you'll find it tightening pores and constricting blood vessels to do its job. It's a coagulant that thickens blood cells to stop bleeding and simultaneously has a soothing, cool, refreshing sensation on the skin. It also kills surface bacteria.

Surprising as it may be, alum's versatility doesn't stop there: It's also a great natural deodorant. It's probably not a better first-choice than your favorite scented deodorant, but all those crystal deodorants in the store are just slightly refined versions of a pure alum block.

The crystals come in different shapes and sizes. You can get a big block if you're just using it at home as part of your regular shaving routine, but you can also get a smaller bar for travel or a more precise application.

The type of razor you use to shave doesn't affect the post-shave routine. An alum block should be part of every traditional wet shaving kit, regardless of the razor you choose.

How To Use An Alum Block

How to use the antiseptic properties of alum blocks

Step 1: After you finish shaving, wash your face to clear any remaining soap or shaving cream residue. Splash your face with cold water. This helps to close and tighten pores and allows the alum block to easily glide over your face. Just gently rubbing the wet alum block on your skin will lightly exfoliate your pores.

Step 2: Wet the alum block with cold water before applying it to your face. Make sure the entire surface is wet. 

Pro tip: You can soak an alum block in ice water before you use it for an increased cooling sensation—especially if you're prone to nicks, cuts, or razor burn. Or if the razor blade wasn't as sharp as you would've liked, if this is the case you might want to revisit our previous post on how often should you change your safety razor blade.

Step 3: Massage the block gently across the areas of your neck and face that you shaved. Rub gently because of its astringent qualities, and you should expect to feel a bit of tightness and tingling or a mild burning sensation. This is expected; it's just the alum crystal and the salicylic component of natural potassium alum doing its magic. 

*If you have sensitive skin do not leave alum block on for more than 20 seconds.

Let the alum residue sit on your skin for about 15 to 20 seconds—roughly the same amount of time it takes to sing Happy Birthday twice or the ABC song. This allows the crystals to shrink your pores and sanctify your skin. Then rinse the residue off with cold water.

Step 5: Apply moisturizer to your freshly shaved skin and apply an aftershave balm or aftershave product as needed such as a high-quality moisturizing cream, aftershave, or shave balm with natural ingredients.

Pro tip: One of my favorites to cool razor burn and for a true cold shock is to use Barrister and Mann terror aftershave.

Alternatives To Alum Blocks For Wet Shavers:
The Styptic Pencil

Alternatives to alum blocks for wet shavers: the styptic pencil

The most popular alternative to alum blocks is the healing styptic pencil, which is sometimes called an alum pencil or alum pen.

A styptic pencil is a medicated stick made from the same compounds as the alum block but in a compact form which makes it a great addition to your traveling dopp kit. The pencil is just in a powdered form and has a wax binder, all compressed into a lipstick-sized compact shape.

Because it has a small tip, it's much easier to target a specific nick or cut with a styptic pencil than it would be with a big alum block. Styptic pencils are even used by militaries to help stop bleeding. They generally work better for small cuts than Band-Aids, which can trap bacteria and fester.

How do you use a styptic pencil?

How do you use a styptic pencil

Step 1: Finish shaving and rinse your face with cold water to close up your pores.

Step 2: Wet the styptic pencil and gently apply it to your face with a little bit of pressure—but not too much—to treat nicks and shaving cuts and to stop any bleeding. You might feel some stinging here, but that's a sign that the pencil is doing what it's intended to.

Step 3: Unlike the alum block, you don't wash off the pencil residue after just 15 or 20 seconds. The pencil residue should stay on your face for a few minutes so it has enough time to seal up the cuts. Make sure the bleeding has completely stopped before you wipe it off your face.

Alum blocks frequently asked questions

Alum Block Frequently Asked Questions and aftershave products using an alum block

Why is the alum block so popular right now?

There's been a lapse in how commonly used the alum block is in the ordinary man's shaving routine, but it was popular just a few decades ago.

They're generally seen as an old-school wet shave accessory, but they're becoming trendy again as an all-natural treatment among a growing number of men who are becoming more intentional about their shaving habits.

The alum block or alum stone has since been used by barbers and embraced by the shaving community as an important step in the post-shave process. Simply put, an alum block should be part of every man's shaving kit whether shaving with a safety razor or straight razor.

How do you store an alum block? 

After you're finished with it, rinse the alum stone with cold water so it's fully cleaned off. Then dry the alum block completely with a dry towel and store it in a cool and dry place where the air circulates. It's important that the block isn't wet at all: If the potassium alum retains moisture it will start to dissolve and its lifespan will shorten. If your alum came with a plastic case, use that for storage.

Can you use alum every day?

You can. Just be aware that if you have dry or sensitive skin, it could dry out your face. For people with oily complexions, it's probably fine. Alum is an astringent, which means it will draw moisture from the skin.

Even if your skin isn't particularly sensitive, you probably shouldn't use it more than twice a day. If you use alum a lot, you could find your skin overcompensating for the antiseptic properties by producing more oil than it naturally would. Don't do it too much; you don't want greasy skin.

How long does an alum block last?

The lifespan depends on the size of the alum stone, how often you use it, and how you store it. If you have a standard 50 to 70-gram block and you care for it properly and use it once a day, you can expect it to last two years or more.

Can I use both alum and aftershave?

Some people like to use both, and others don't. It's a matter of personal preference. Some people find that alum's astringent properties and the alcohol content of aftershaves tend to dry out their skin. It's worth testing alum block shaving on its own then with aftershave to see what works best for your skin.

Can you use alum blocks as a natural deodorant?

You can actually use it under your arms as an alternative to traditional deodorant. It's often marketed as "crystal deodorant." It's not an antiperspirant, so it won't stop you from sweating, but it might stop the smells depending on how your body's chemicals interact with the mineral salts. Maybe try it out after your next shave.

Where can I buy an alum block?

Alum blocks come in various forms, such as blocks, pencils, and sometimes they're even infused in shaving soaps. Online shops that sell professional shaving products and kits will sell alum blocks. Make sure to purchase a high-quality alum stone because poorly made alum stones can start falling apart bit by bit and all you are left with is a pile of dust whereas a finely made alum bar can be used for years. Search for the pre and aftershave section of products and choose the best size based on your lifestyle and how often you plan to shave.