We use the two terms interchangeably. But is isopropyl alcohol the same as rubbing alcohol? Not necessarily, but the difference may or may not matter, depending on what you’re using it for. Let’s look at isopropyl alcohol vs rubbing alcohol.
Rubbing alcohol can be either isopropyl or ethyl alcohol, but the main difference is purity. Rubbing alcohol is 70% pure, where products sold as isopropyl alcohol are typically 91% or 99% pure.
Isopropyl alcohol vs rubbing alcohol
There are two or three major differences between isopropyl alcohol and rubbing alcohol. They are, in no particular order:
- rubbing alcohol could also be ethyl alcohol
Rubbing alcohol is usually cheaper because it has more water in it, and water is cheaper than alcohol. The more pure the alcohol is, the more it costs. Rubbing alcohol is between 68 and 72 percent pure, usually rounded to 70 percent. The major difference between the two at 70% concentration is marketing. If you see rubbing alcohol and 70% IPA side by side, don’t pay extra for 70% IPA. It’s not worth paying a premium.
For first aid uses, rubbing alcohol is usually what you want. For other uses, such as cleaning electronics, you want a higher purity. The higher purity means less residue left behind, and since residues usually aren’t conductive, you’re more likely to fix the thing you intend to fix instead of breaking it if you use 99% isopropyl alcohol. If 91% is all you can get, it’s still better than 70%.
For general disinfecting, 70% is usually the optimal concentration.
The words isopropyl alcohol, isopropanol, and IPA are used interchangeably.
As for cost, my local pharmacy normally sells 16 ounces of IPA for $1.99, and 32 ounces of rubbing alcohol for $2.49. So for 25% more, you get twice as much product. Sometimes the more expensive product is better. But not always.
When to use rubbing alcohol instead of isopropyl alcohol
A 70% concentration is a better disinfectant, generally speaking. This is because it evaporates more slowly, so it stays on the surface longer and gets more time to do its work. It also causes a less catastrophic injury on initial contact, so the bacteria or virus doesn’t react to it as quickly. So the 70% concentration gets a chance to sneak up on its defenses and kill it, where a more potent alcohol won’t.
It’s counter-intuitive, but for first aid, a less potent 70% concentration tends to work better.
But this isn’t a case of lower always being better. You can find 50% isopropyl alcohol at some stores. At that concentration, it’s still effective, but less effective than 70%. And 50% is the minimum effective concentration. If the 50% stuff is all you can get, then of course you don’t have a lot of choice. But if you can get 70%, regardless of whether the label calls it rubbing or isopropyl alcohol, that’s the one you want.
Rubbing alcohol for cleaning
The same goes for cleaning when your goal is to disinfect surfaces, such as cleaning doorknobs and light switches during cold and flu season. If you’re trying to kill germs, isopropyl alcohol vs rubbing alcohol is no contest. You want the cheaper rubbing alcohol, even though your instinct says the opposite.
When to use a higher concentration
When you’re cleaning electronics, or anything electrical for that matter, like model train tracks, you want a higher concentration. The higher concentration is more potent on whatever impurities you’re trying to dissolve, especially when you may be dealing with grease or oil. It dries faster, to let you get back to work faster. And in theory at least, it will leave behind less residue. The ideal stuff to use is 99% IPA, but 91% will do if it’s all you can get. Your state or local regulations may keep you from being able to get 99 percent.
If you’re trying to kill grease and oil, isopropyl alcohol vs rubbing alcohol is no contest. Pay the extra money. When you need a solvent, the higher, more expensive concentration is better. Your instinct is correct in this case.
Of course, at the time I’m writing this, alcohol is in short supply due to COVID-19. For hobby work, you can use mineral spirits as an alternative. Alcohol is safer and more pleasant to work with than mineral spirits. But for hobby work, mineral spirits is probably more readily available at this time, and then you’re keeping more of a vital material available for medical use at a time we need it. Mineral spirits will dissolve grease, oil, and solder flux. It’s available in hardware stores, usually in the paint section.
And I’m sorry if this goes without saying for you, but I must say it. Please, please don’t try to use mineral spirits for first aid. It’s useful for fixing things, but not for treating humans.