A is for: (Isopropyl) Alcohol

This is intended as the first of a series of posts in which I discuss (ramble, pontificate) about cosmetic ingredients.  I may dive down the occasional rabbit-hole to explore things that aren’t strictly ingredients.  Let’s just see where this takes us.

I’m starting with A is for Alcohol.  It’s very unlikely that I’ll work through the alphabet, but my plan is to create an alphabetical list as I add other posts.

In this case A is for a specific kind of alcohol.  Its names include isopropyl alcohol, isopropanol,  2-propanol and propan-2-ol depending on the naming convention you follow.  I’m going to stay with isopropyl alcohol.

Americans often refer to isopropyl alcohol as Rubbing Alcohol, possibly to distinguish it from what the British might call quaffing alcohol (ethanol).  Isopropyl alcohol is unpalatable and toxic, so it doesn’t attract the attention of tax collectors to the extent that ethanol does in most countries.  It’s readily available as 99.9% isopropyl alcohol, but it’s more commonly sold as a mixture of 70% isopropyl alcohol and 30% water by volume.  The 70% mixture is good for all the uses I’m going to discuss below.  A litre of 70% isopropyl alcohol should cost no more than GBP 8.00.  I think it’s a good investment.

(In Britain there is a concoction called surgical spirit based on methyl alcohol.  American Rubbing Alcohol and British Surgical Spirit are different.  In many contexts they can be used interchangeably, but some versions of Surgical Spirit include fragrances (notably Wintergreen) and so they aren’t suitable for cosmetic uses.)

Antiseptic

Isopropyl alcohol is used as a topical antiseptic.  If a doctor or nurse swabs your arm before pushing a needle into it, it is likely that they are using isopropyl alcohol.

The main ingredient in pre-packaged antiseptic wipes is normally isopropyl alcohol.  The 70% version is more effective as an antiseptic than the 99.9% version because water opens up the pores of bacteria so the alcohol can penetrate and kill them.  Isopropyl alcohol on cotton wool is good for cleaning minor cuts and skin abraisions.  Somewhere I’ve seen a suggestion that it can be used as an antiseptic on nappy (diaper) rashes and intimate parts of the human anatomy.  I’m sure it would be effective, but I wouldn’t want to be around to hear the scream.  It can sting painfully.

I use isopropyl alcohol as an antiseptic for swabbing down worksurfaces and for spritzing the containers I use for cosmetic preparations.  I have a small bottle with a flip top that I can use to moisten pieces of paper kitchen towel, and I have a small spray bottle that I can use for spritzing.

Solvent

Isopropyl alcohol mixes with many oils and greases, as well as mixing with water.  Isopropyl alcohol (including the 70% version) evaporates completely without leaving a residue.  That makes it a very useful cleaning agent.  Those lens wipes that your optician sells?  They are impregnated with isopropyl alcohol.  That cleaning spray for your whiteboard?  Probably isopropyl alcohol.  That cleaner for your computer screen?  Probably isopropyl alcohol.

I use my spray bottle of isopropyl alcohol, along with either kitchen paper towel or a facial tissue, for cleaning eyeglasses, computer screens, windows and other hard surfaces.  It’s pretty effective on the grime that accumulates on the inside of a car windshield, the kind that makes driving into sunlight rather challenging.

I try to re-use bottles and containers made of glass or plastic.  Removing manufacturers’ labels can be challenging (involving a lot of cursing).  Isopropyl alcohol will remove some of the adhesive deposits left on glass or plastic surfaces.  (It doesn’t always work.  My solvent of last resort for label adhesives is parafin.  I use a clear, unscented lamp oil because it evaporates without leaving a residue, in much the same way as isopropyl alcohol.)

 

Curiously, although isopropyl alcohol and water mix freely in any proportions, isopropyl alcohol doesn’t mix with water containing common salt.  Adding some salt to any mixture of isopropyl alcohol and water causes the alcohol to separate out of the mixture.  The alcohol is less dense than the brine, so floats on the top.  This is a process called “salting out”.  Of course I tried it at home …

It took a lot of salt to persuade the alcohol to separate out, and a little vegetable dye to make the boundary between the layers visible in a photo.  The proportions of the layers suggest that the brine (on the bottom) still contains some alcohol.

Drying aid

Isopropyl alcohol mixes with water, and the mixture has a much lower surface tension than water.  So adding isopropyl alcohol to water causes droplets to collapse and the resulting mixture evaporates faster than the water would if left untreated.

I put a few drops of isopropyl alcohol into glass bottles after I’ve washed them, then give them a shake.  The inside of the bottles dries faster.

There is a product called Swim-eze that is used by swimmers and divers to dry and disinfect their ears afer swimming or diving.  A few drops in each ear is very effective.  A 30ml bottle of Swim-eze sells for around GBP 12.00.  That’s GBP 400.00 per litre.  The content?  Just 95% isopropyl alcohol and 5% glycerine.

Perfumes and Cosmetics

Although I’ve seen isopropyl alcohol listed as a cosmetic ingredient for lotions and aftershaves, I don’t generally use it as an ingredient in my preparations.  Mostly I prefer to use ethanol as a lighter alternative.

There is just one exception (Frog’s Breath) which I’ll save for a later post.

That is not to say that I don’t use isopropyl alcohol when I’m making cosmetics – I use it as a disinfectant and a solvent for cleaning before and after a making session.  The heavier essential oils are very viscous and some are very sticky.  They coat the surface of droppers and pipettes.  With a little persistence it is possible to remove the deposits with isopropyl alcohol.

Cautions

Isopropyl alcohol is toxic if ingested in any quantity, and it’s flammable.