No Sweat - Potassium Alum
Today's star is a staple in my stock and present in all of my deodorants. Its chemical formula is shown above. It belongs among the privileged few ingredients that have a pronounceable INCI name: Potassium Alum.
What is it?
Potassium alum is 'the potassium double sulphate of aluminum'. It is derived from the oxidation of sulfide minerals and potassium-bearing minerals. In short, it shows up as encrustations on rocks (that contain sulfide and potassium-bearing minerals) when they come into contact with air (well, not so much air as oxygen molecules, but you get the drift). You may already know these encrustations as 'natural crystal deodorant', because potassium alum is shaped and sold in solid form as such.Where's it From
Potassium alum is naturally occurring and can be found all around Europe, North and South America and parts of Asia (check the pictured map for potassium alum hotspots).Can it Be Made Synthetically?
Yes, it can. As far as I understand, you have to be a fairly mineral-savvy person to distinguish a synthetic potassium alum crystal from a naturally occurring one. Synthetically made crystals will have a different opacity due to the presence of aluminum hydroxide.So What's The Diff?
Naturally occurring potassium alum is preferred for cosmetics use because it has no aluminum hydroxide. The synthetically made crystals can be a mild skin irritant due to the aluminium hydroxide content.
Does it Deodorise?
In a word, yes. However (there's almost always a however, isn't there?) – potassium alum can't carry a full day of deodorising action all by itself. If you don't mind applying deodorant every few hours, it's fine. But I do mind. Therefore, I combine it with other actives to create a deodorising cocktail that works as long as a commercial deodorant.You Can Eat it Too
Potassium alum is used in various areas (among these: water purification and leather tanning) but you may very well already have potassium alum on your kitchen shelf. Can you guess where? Potassium alum is used as the acidic component of some baking powders.Speaking of Which
There are several recipes around on how to do a simple DIY baking-soda based deodorant. These deodorants are reported to work, but are unfortunately also often accompanied by a skin reaction after a short period of use. I've read accounts of everything from a mild redness to serious rash forcing the person to stop use (with subsequent nursing of armpits for a period of time). I have a sneaking suspicion that it is the presence of aluminium hydroxide and sodium aluminum phosphate (or perhaps even some of the other more acidic components found in baking soda) that could be the culprits. Sodium aluminium phosphate is produced from aluminium, phosphoric acid and sodium hydroxide and is not allowed for use in foodstuffs in Japan and some European countries due to its aluminum content. Despite also reading many positive accounts on how well a baking-soda deodorant works (if you can get past the almost inevitable period of rash and irritation), I'll readily admit that I would want to do a bit more research into the specific components of baking soda before feeling comfortable about giving this a try.Find The Other Posts in This Series Right Here
No sweat - how does deodorant workNo sweat - the basic make-up of deodorant
Updated post on Potassium Alum
Do Tell
Have you ever made and used a DIY baking soda deodorant? Did it work for you without any skin irritation?Please see an updated post on potassium alums deodorizing capabilities here.
Comments
I am a longtime 'lurker' on your excellent blog. Most of the DIY baking soda-based recipes use baking soda, which is pure sodium bicarbonate - not baking powder, which is sodium bicarbonate plus acid salts (including aluminum salts).
I've wondered about why people get when they use baking soda deodorants (including LUSH's discontinued Aromacreme)... I have a couple of guesses: the first is that baking soda is so abrasive that delicate underarm skin just can't take it after a while; and my second guess is that you end up with little granules of sodium bicarbonate all over your skin, so that when you sweat, you have a locally saturated alkaline solution (pH 9 or more, it seems?), which irritates skin after a while. I'm curious to know what you think of these guesses!
Thanks for your great blog!
This is now officially on my to-do list - find out exactly what it is that causes the abrasive reaction to baking soda deodorants. I will dedicate a post to this soon. Thanks again!!
I noticed the plain deo works quite well at blocking and absorbing odors for most of the day but if you add clove E.o. it works for the whole day and clear into the evening. Even if you go to the gym after work.
Also, clove EO can be a skin irritant.. but I'm guessing you are using a very low dose..? (I imagine the scent is absolutely divine!)
Rebecca
I used to make a great deodorant with Chitosan. You have to get it to an acid pH to liquefy. Works well though.
Rebecca
Thanks for your input! Interesting idea with the aloe and potassium alum for your dogs! I've actually never heard of doing this before and wonder how it goes for you. Please do keep me posted!
As to the Chitosan - I'm not sure as to how this is an effective deodoriser? I only know it as a medical application. Could you elaborate on how you used it?
1. I only get irritation when I use it just after shaving...and sometimes in the middle of an extra hot and sweaty summer.
2. Baking soda works ok. Coconut oil works a little. Together they work wonderfully. Normally I use them mixed together into a convenient stick.
3. Shaving irritation is prevented by rubbing coconut oil onto armpits first, then patting on a little baking soda on top. This protects the skin from the baking soda. For the summer irritation, this seemed to result in happy skin where the coconut oil had been applied, with a ring of redness around it.
4. This seems to support the theory about baking soda making a high-ph solution when mixed with sweat. Maybe heavier sweaters are more prone to reactions than lighter sweaters like myself?