How Do Bath Bombs Work? The Science (With Video)



Bath bombs are awesome balls of fizzy goodness, with some interesting science behind them! They were invented in 1989 by Mo Constantine, one of Lush’s founders. Bath bombs contain the chemical sodium bicarbonate, also known as baking soda, as their key ingredient.

This is the text version – scroll down for the video!

Some of you might remember that baking soda isn’t good for your skin because it’s a base, with a high pH. High pH (alkaline or basic) products disturb the skin’s acid mantle, which protects your living tissue from the environment, particularly bacteria, like acne-causing Propionibacterium acnes.

But don’t fret! The second key ingredient in a bath bomb is a solid acid, such as citric acid or tartaric acid (cream of tartar). This lowers the pH by reacting with the baking soda when water is added to the mixture. Unless the maker of the bath bombs has really messed up their proportions, the final pH should be reasonably neutral. Until the water dissolves the acid and baking soda and allows them to mix at a microscopic level, nothing happens.

Aside from neutralisation, the acid + base reaction with sodium carbonate also produces tiny bubbles of carbon dioxide gas, which is what causes the fizzing:

Citric acid + sodium bicarbonate → sodium citrate + water + carbon dioxide

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How Do Bubbling Oxygen Masks Work? (with Video)

How Do Bubbling Oxygen Masks Work?

Oxygen masks are products which come out of the bottle as a gel, but start bubbling with oxygen gas after a few seconds on the skin. Brands like Bliss, Peter Thomas Roth, Dr Brandt, Oseque and Sephora have oxygen bubble masks. What do they do, and how did they get the gas into the bottle?

Here’s the video, scroll down for the text version…

How do oxygen masks work?

Oxygen masks work a lot like soda water or soft drinks, where gas is dissolved in water under pressure (carbon dioxide gas, for soda), and is released when the pressure drops (when you open the bottle).

How Do Bubbling Oxygen Masks Work?

Oxygen doesn’t dissolve as well in water, so instead it’s dissolved in chemicals called perfluorocarbons, which are stable, unreactive carbon-based compounds containing fluorine atoms. They can dissolve 20 times more oxygen than water, and have even been investigated for use in artificial blood.

These oxygenated perfluorocarbons are then sealed in a pressurised bottle. When the mask comes out, the oxygen starts fizzing out slowly like the bubbles in soft drink. For some thicker products, a pressurised bottle isn’t required – the thickness of the product itself is enough to hold the oxygen until you massage it out by applying it on the skin.

How Do Bubbling Oxygen Masks Work?


The most commonly used perfluorocarbons in cosmetics are perfluorodecalin and methyl perfluorobutyl ether, but pretty much anything in the ingredients list with “perfluoro” in it will be a perfluorocarbon. Here are the perfluorocarbon ingredients in some popular oxygen masks:

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Powered By Chemicals Coffee and Tea Molecule Mugs

Earlier this year I really wanted a molecule mug, but I could only really find ones with caffeine on them. But the chemistry of tea and coffee is so interesting – there’s EGCG in green tea for example, an awesome antioxidant that you’ll also find in skincare products, and there’s a bunch of scent molecules in coffee that smell nasty …

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How Does Olaplex Hair Treatment Work?

Olaplex 2 & 3: How Does Olaplex Hair Treatment Work?

What is Olaplex?

Olaplex is a line of hair repair, “bond building” treatments that’s getting heaps of buzz in the hair community, especially with people who have damaged hair from excessive bleach. It’s available in a couple of forms – Olaplex can be mixed in with bleaching products to minimise damage, or it can be used as a separate treatment. Here’s the science behind how it “repairs” disulfide bonds in hair.

Note (August 2018): I’ve updated this post, and there’s a video version now as well – click here to watch it!


The active ingredient in Olaplex is a compound called bis-aminopropyl diglycol dimaleate. This is a slightly ambiguous name, but I’m pretty sure it matches this structure in the patent:


What does Olaplex claim to do?

Olaplex claims to “reconnect broken disulfide sulfur bonds in the hair.” The treatment is labelled a “bond multiplier”, which limits damage to hair during or after colouring.

A lot of people with damaged hair have managed to get amazing results from Olaplex. Here’s my friend Mary, who got her natural curl texture back with a single Olaplex treatment:


So suffice to say, it definitely does something! But is it as revolutionary as the hype makes it out to be?

How does Olaplex’s claims stand up?


First up, a bit of basic hair chemistry. I’ve posted about hair chemistry before in my explanation of how hair straightening and perming work, but here’s a quick recap:

Hair contains lots of keratin proteins, which has the amino acid cysteine. Cysteine is special because it contains a sulfur (S) atom. Normally, two sulfurs will join together to form a disulfide bond (S-S), creating a link between two proteins:

All these proteins holding hands is partially responsible for your hair’s overall shape and strength. When hair is permed or straightened, these bonds are deliberately broken into two SH (“free thiol”) groups, and then reformed after the hair is pulled into its new shape. Re-forming these bonds typically takes a few days (hence not washing your hair for a few days after perming, since it warps the shape).

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Surfactants Are Everywhere, aka Stop Being Terrified of Chemicals

Surfactants Are Everywhere, aka Stop Being Terrified of Chemicals

This post was originally published on the now sadly defunct awesome website The Toast in 2014. A reader suggested that I repost it on Lab Muffin… which I thought I did, but apparently that was all a fever dream. Here it is!

There’s soap in your mayonnaise!

As a scientist with a degree in chemistry, the surge in chemophobia over the last five years has been both baffling and frustrating.

While there are plenty of toxic substances that we should be well frightened of, there are also many safeguards against their use – by and large, the chemicals you encounter in your day-to-day life are benign, even the ones with the scary unpronounceable names and the ones made from substances that can literally chew your face off (sodium chloride, I’m looking at you). But it’s incredibly easy to fall into the trap of common-sense-based marketing. Scientific literature is not exactly reader-friendly, and scientists have a long history of alienating themselves from Normal People.

Surfactants Are Everywhere, aka Stop Being Terrified of Chemicals
“Just kicking back with a brewski in my favourite fuck-off flask. What’s with the side-eye?”

There’s one particularly painful tactic which anti-chemical lobbyists love to use, and that is the faulty generalization. You’ve no doubt seen it enough times already…

  • “I had the flu vaccine and still got the flu, therefore vaccines don’t work.”
  • “This chemical gave rats cancer in a study, we need to take it out of our shampoo/food/clothing!” (Despite the fact that the rats used in these sorts of studies are specifically bred to grow tumors like they’re going out of style, and to receive the amount the rats did, you’d have to mainline a swimming pool’s worth of shampoo/food/clothing every week.)
  • “Mineral oil comes from crude oil, therefore you’re rubbing petrol on your face! Use our natural, organic face cream instead, because you know exactly what’s in it.” (Which is ironic, since natural products are notoriously variable in composition.)
  • “It contains chemicals! Chemicals are bad.” (Except for the million or so chemicals that you unwittingly use every day to stay alive, like oxygen and water and neurotransmitters, one of which is pretty much MSG dissolved in water.)

To demonstrate how easy it is to make these grand leaps from benign facts to chemophobic, scaremongering argumentum ad Natural News, let me introduce you to my lovely assistant, surfactants, one of my favourite categories of chemicals (yes, chemists all have their favourite chemicals, it’s a disease.)

Chemicals can be roughly divided into two broad categories. On one side are the hydrophiles, which dissolve readily in water, and are highly charged, which lets them interact favourably with other highly charged things – common examples are water, salt, and ethanol (drinking alcohol.) On the other side there are lipophiles, which are oily, and tend to be weakly charged or neutral. The two don’t interact favourably enough to hang out together in a happy stable mix, and despite any amount of violent shaking, they invariably separate and go to their respective sides.

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Why Vitamin C Can Stain Your Skin (and How to Avoid It!)

Why Vitamin C Can Stain Your Skin (and How to Avoid It!)

Vitamin C is one of the few skincare ingredients with a ton of independent research to back up its properties, like its brightening and anti-wrinkle benefits. Those of you who are vitamin C enthusiasts may have noticed that with some vitamin C serums, you end up with slightly stained orange-brown skin after a few days of use – sort of like fake tan. I’ve often wondered why but didn’t really dig into it past a quick Google search (which found nothing), so I just put it off as a weird side effect of vitamin C oxidising.

But recently, I came across a diagram in a peer-reviewed paper on a completely different topic that accidentally told me exactly why vitamin C does this: ascorbic acid eventually oxidises to erythrulose!

Why Vitamin C Can Stain Your Skin (and How to Avoid It!)

As most of you may know, vitamin C in the form of ascorbic acid oxidises easily to dehydroascorbic acid, which has an orange-brown colour. It does this when it’s stored in water, as well as on your skin. Oxygen and light exposure will speed up the oxidation reaction. This reaction is reversible, so you can get back the ascorbic acid if you have the right antioxidants in the formula.

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Do I Need a Special Cleanser to Remove Sunscreen?

Do I Need a Special Cleanser to Remove Sunscreen?

Here’s a myth I’ve been seeing around skincare communities: that you have to use a special cleanser to remove water-resistant sunscreen. For example:

“Keep in mind that most of these sunscreen actives are also oil-soluble (only dissolves in oil, not water), which gives sunscreens their water-proof and sweat-proof properties. Therefore, in order to completely remove sunscreen, you have to use an oil, cleansing oil, emollient cleanser, or makeup remover of some kind.” (Source: Skinacea)

Have we all been leaving sunscreen on our faces before we discovered the magic of double cleansing??

Do I Need a Special Cleanser to Remove Sunscreen?

How Do Cleansers Work?

Luckily, the answer is no. A regular cleanser will remove waterproof sunscreen! The reason for this is surfactants.

Surfactants are a special class of chemical I’ve mentioned quite a few times before. They look a bit like a tadpole, with a lipophilic (oil-loving) “tail” and a hydrophilic water-loving) “head”.

Do I Need a Special Cleanser to Remove Sunscreen?

(Related posts: How Do Cleansing Balms Work?, How Does Micellar Water Work?, The Science of Face Washing)

Because of this special structure, surfactants can help oil dissolve in water and vice versa. The tail binds to oil while the head binds to water. The surfactants help the oil lift off the skin, forming little oil droplets that end up dispersed in the water as an emulsion (surfactants are also known as emulsifiers for this reason). The droplets can then be rinsed away, leaving your skin clean.

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Video: Why pH matters for AHAs and acids in skincare

Video: Why pH matters for AHAs and acids in skincare

I’ve been a little frustrated with what scientific concepts I can get through in words and crudely drawn illustrations on this here blog. When I teach at my day job, I do a lot of hand-waving, emphatic underlining, symbolic gesturing and smashing together of whiteboard markers, and not having the ability to show movement sometimes feels a bit like I …

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