Devil’s toothpaste is a dramatically scaled-up version of the classic elephant’s toothpaste demonstration, using highly concentrated hydrogen peroxide (30% or higher) instead of the diluted drugstore variety to produce a massive, steaming column of foam that can shoot several meters into the air. The reaction itself is straightforward: a catalyst triggers the rapid breakdown of hydrogen peroxide into water and oxygen gas, and dish soap traps that oxygen into a spectacular cascade of bubbles. The high concentration is what separates the “devil” from the “elephant,” making the eruption far more violent, far hotter, and considerably more dangerous to perform without proper precautions.
What Separates Devil’s Toothpaste From Elephant’s Toothpaste
Elephant’s toothpaste is the version you see at school science fairs. It typically uses 3% to 12% hydrogen peroxide, yeast as the catalyst, and produces a manageable ooze of foam that kids can safely touch. Devil’s toothpaste cranks the concentration to 30% or even 50% hydrogen peroxide, swaps the yeast for a much more aggressive catalyst like potassium iodide, and generates an eruption that can reach the ceiling of a room in seconds. The foam it produces is genuinely hot, often steaming visibly, and will cause chemical burns if it contacts bare skin at those concentrations.
The name “devil’s toothpaste” was popularized by science YouTubers, most famously by Mark Rober in a 2019 video that used enormous quantities of concentrated peroxide and potassium iodide in an outdoor setting. The distinction between the two versions is not a difference in chemistry but a difference in scale and intensity. Every mechanism at work in elephant’s toothpaste is at work in devil’s toothpaste. The concentrated peroxide simply means more oxygen is released, faster, and with far more heat.
What You Need
The ingredients are simple in concept but require caution in practice, especially around the hydrogen peroxide. Here is what goes into a typical devil’s toothpaste setup:
- Hydrogen peroxide (30%+): This is the fuel for the reaction. Drugstore peroxide (3%) will not produce a devil’s toothpaste eruption. You need 30% or higher concentration, which is sold as a laboratory or industrial chemical and is not available at most retail stores. It is a strong oxidizer that can bleach skin on contact and cause serious burns.
- Potassium iodide solution: This is the catalyst. Dissolve potassium iodide in warm water to create a saturated solution. The iodide ions massively accelerate the decomposition of hydrogen peroxide without being consumed themselves.
- Liquid dish soap: A generous squirt of concentrated dish soap is what turns the oxygen gas into foam rather than just letting it bubble away invisibly. Without soap, you still get the chemical reaction, but the visual spectacle disappears.
- Food coloring (optional): A few drops of food coloring in the peroxide mixture before adding the catalyst make the foam more visually striking. Many people swirl multiple colors along the inside of the container for a striped effect.
- A tall, narrow container: A plastic bottle, graduated cylinder, or similar vessel with a narrow opening directs the foam upward. The narrower the opening relative to the volume, the more dramatic the vertical eruption.
You also need safety equipment. Splash-proof goggles, chemical-resistant gloves, and a lab apron or old clothing are not optional when working with 30% peroxide. A plastic tarp on the ground makes cleanup easier, and performing the experiment outdoors or in a well-ventilated space is strongly recommended because the reaction generates both heat and a burst of oxygen gas.
How to Do It
Pour the hydrogen peroxide into your container. Add a generous squirt of dish soap and swirl gently to mix, without creating excessive bubbles. If you are using food coloring, add it now and let it streak down the inside walls of the container for the best visual effect. Prepare your potassium iodide solution separately in a cup or beaker by dissolving the powder in warm water and stirring until dissolved.
When you are ready, stand back and pour the potassium iodide solution into the container in one quick motion. The reaction begins almost immediately. Oxygen gas floods out of the decomposing peroxide, the soap traps it into dense foam, and the whole mixture erupts from the container’s opening. With 30% peroxide and a well-prepared iodide solution, the foam column can rise a meter or more above the container in under a second. The foam will be warm to hot, and the container itself will heat up considerably.
Do not lean over the container when adding the catalyst. The eruption is fast enough to catch you off guard if you have not done this before, and hot foam in the eyes is a trip to the emergency room. Pour the catalyst from arm’s length, or use a funnel with a release mechanism so you can step back before the reaction begins.
The Chemistry That Powers the Eruption
Hydrogen peroxide naturally breaks down into water and oxygen gas over time. This is why the bottle of peroxide in your medicine cabinet gradually loses its fizz. What the catalyst does is speed up this decomposition dramatically, turning a reaction that would take weeks or months at room temperature into one that completes in seconds.
The overall reaction is simple: two molecules of hydrogen peroxide yield two molecules of water and one molecule of oxygen gas. The energy needed to break the oxygen-oxygen bond in peroxide is lowered by the catalyst, so the decomposition happens explosively fast rather than at a slow trickle. The oxygen gas is what inflates all those soap bubbles into the towering foam column.
The mechanism by which the catalyst achieves this depends on what catalyst you use. With iron-based catalysts, researchers have described two competing pathways. One involves a cycle where the metal ion is repeatedly reduced and oxidized, generating reactive oxygen species along the way. The other involves the metal forming a direct complex with the peroxide, breaking the oxygen-oxygen bond in a single step rather than through intermediate radicals.1International Journal of Chemical Kinetics. Kinetics and mechanisms of decomposition reaction of hydrogen peroxide in presence of metal complexes With manganese dioxide, a common catalyst in classroom demonstrations, the peroxide adsorbs onto the surface of the solid particles, and the decomposition proceeds through intermediate reactive oxygen species that propagate the reaction in solution.2PubMed. Hydrogen peroxide decomposition on manganese oxide (pyrolusite): kinetics, intermediates, and mechanism
With potassium iodide, the mechanism is different again. The iodide ion donates an electron to the peroxide, splitting it into water and a reactive oxygen atom. The iodide is then regenerated in a follow-up step, which is what makes it a true catalyst rather than a reactant that gets used up. This catalytic cycle is extremely fast at high peroxide concentrations, which is why potassium iodide is the go-to catalyst for devil’s toothpaste rather than the slower-acting yeast used in the classroom version.
Why Catalyst Choice and Particle Size Matter
Not all catalysts produce the same eruption, even with identical peroxide concentrations. Yeast works as a catalyst because the enzyme catalase inside yeast cells breaks down hydrogen peroxide, but the reaction rate is limited by how quickly the peroxide can reach the enzyme inside the yeast cells. This makes yeast ideal for the gentler elephant’s toothpaste but too slow for the devil’s version.
Potassium iodide in solution reacts almost instantly because the iodide ions are already dissolved and can contact the peroxide molecules freely. Manganese dioxide works as a solid-surface catalyst, and here the physical form of the catalyst becomes crucial. When researchers compared two different particle sizes of manganese dioxide in 30% hydrogen peroxide, they found that the finer particles (around 10 micrometers) produced a dramatically faster reaction than coarser particles (around 44 micrometers).3ResearchGate. Observations on Manganese Dioxide As a Catalyst in the Decomposition of Hydrogen Peroxide: A Safer Demonstration The reason is surface area: smaller particles expose more total surface to the peroxide, giving the reaction more sites to occur simultaneously. If you are using a solid catalyst rather than a dissolved one, grinding it finer will produce a more vigorous reaction.
This particle-size effect is actually useful for safety. If you want to demonstrate the chemistry without the full-blown devil’s toothpaste violence, using coarser manganese dioxide with concentrated peroxide can give you a slower, more controlled foam that is easier to manage in an indoor setting. The same paper noted that manganese dioxide offers a safer alternative for classroom demonstrations precisely because teachers can tune the reaction speed by selecting the particle size.3ResearchGate. Observations on Manganese Dioxide As a Catalyst in the Decomposition of Hydrogen Peroxide: A Safer Demonstration
How Soap Turns Gas Into Foam
Without dish soap, the decomposition of hydrogen peroxide would just produce bubbles that pop at the surface of the liquid, releasing oxygen into the air. It would look like a pot of water boiling violently but would not produce the signature towering column. The soap is what transforms a chemical reaction into a spectacle.
Soap molecules have one end that attracts water and another that repels it. When oxygen gas pushes through soapy liquid, each bubble gets coated in a thin film of soap-stabilized water. These bubbles stack on top of each other rather than immediately popping, building the foam column upward. The foam behaves as a semi-solid material with its own interesting physics. Researchers studying liquid-gas foams have found that they behave roughly like a material that resists flowing until a certain force is applied, after which they flow more easily. The mechanical properties of the foam, including how stiff it is and how readily it yields, depend on the size distribution of the bubbles and the ratio of gas to liquid.4International Journal of Heat and Fluid Flow. A rheological model for a liquid-gas foam
In practical terms, this means the type and amount of dish soap you use changes how the eruption looks. More soap generally produces denser, stiffer foam that holds its shape longer. A thinner soap solution makes lighter, more ephemeral bubbles that collapse quickly. Some people experiment with different brands of dish soap or add small amounts of glycerin to stabilize the bubble walls further, though glycerin is not necessary for a good eruption.
The Heat Factor
The decomposition of hydrogen peroxide is exothermic, meaning it releases heat. At low concentrations like the 3% you buy at the pharmacy, this heat is negligible. At 30% or higher, the heat generated is substantial enough to produce visibly steaming foam and to make the container hot to the touch. In very large-scale demonstrations using 50% peroxide, the foam can emerge at temperatures well above 60°C (140°F), which is hot enough to scald skin.
This is the single biggest safety difference between elephant’s toothpaste and devil’s toothpaste. A child can safely stick their hands into elephant’s toothpaste foam made with 3% peroxide. Touching devil’s toothpaste foam can cause thermal burns, and any unreacted peroxide in the foam at 30% concentration can cause chemical burns on top of that. The combination of heat and oxidizing chemistry is why devil’s toothpaste should always be treated as a demonstration to watch from a distance rather than an activity to touch.
The heat also affects how much oxygen is released. Higher temperatures speed up the decomposition further, creating a brief feedback loop where the reaction heats itself and accelerates before the peroxide runs out. This self-accelerating behavior is part of why the eruption is so sudden and violent compared to the slow ooze of the yeast-based version.
Scaling Up and Shaping the Eruption
The shape and size of the container has an outsized effect on how the eruption looks. A tall, narrow-necked bottle concentrates the foam into a single vertical column, giving you the classic toothpaste-squeezing-out-of-a-tube look. A wide-mouthed container produces a broader, mushroom-shaped eruption that spreads outward more than upward. Multiple bottles arranged in a cluster, each triggered simultaneously, can create patterns or competing foam columns.
People who do this at large scale for videos or public demonstrations typically use several liters of peroxide and proportionally scaled catalyst. At that volume, containment becomes a real concern. The foam spreads across whatever surface it lands on, and concentrated peroxide can bleach or damage decks, driveways, grass, and clothing. A large plastic tarp, a kiddie pool as a catch basin, or performing the demonstration on a surface you do not mind staining are all standard precautions for big setups.
The timing of the catalyst addition matters as well. Pouring the potassium iodide solution in slowly produces a sustained eruption over several seconds. Dumping it all in at once creates a single explosive burst. Some demonstrators use a bucket with a pull-away mechanism so the entire catalyst solution drops in simultaneously from above, which gives the most dramatic single-shot eruption.
Safety Beyond the Basics
Concentrated hydrogen peroxide is classified as a strong oxidizer and a corrosive substance. Beyond the burns and heat already discussed, there are a few less obvious hazards worth knowing about.
First, the reaction releases a large volume of oxygen gas very quickly. In a confined indoor space, this sudden oxygen enrichment is a fire hazard. Anything flammable in the immediate area becomes easier to ignite in an oxygen-enriched environment. This is another strong reason to do devil’s toothpaste outdoors or in a very well-ventilated area, and to keep open flames, sparks, and heat sources away from the demonstration.
Second, storing concentrated hydrogen peroxide itself requires care. It should be kept in its original container, away from heat and light, and never transferred to a metal container, since metals can catalyze slow decomposition even in storage. A sealed container of slowly decomposing peroxide can build up oxygen pressure over time, which is why laboratory peroxide bottles have vented caps.
Third, cleanup requires thought. The foam itself is mostly water, soap, and dissolved catalyst, which is relatively harmless once it cools and the peroxide has fully decomposed. But if the reaction was incomplete and unreacted peroxide remains in the foam, it can still bleach or irritate skin. Rinsing the area with plenty of water after the foam has cooled is the simplest cleanup approach. The potassium iodide in the runoff is not toxic in small amounts but should not be dumped into storm drains or natural waterways in large quantities.
Why It Works So Well as a Teaching Tool
The elephant’s toothpaste demonstration, and by extension devil’s toothpaste, has become one of the most widely used chemistry demonstrations in schools around the world. Educational researchers have noted that the experiment can be adapted for different age groups and different chemistry concepts. At a junior level, it illustrates basic ideas about elements, compounds, and mixtures. At a senior high school level, it can be used to teach reaction rates, catalysis, and exothermic reactions.5ResearchGate. Elephant’s toothpaste: review of exciting chemistry learning in senior high school
The appeal is obvious: the reaction is visually dramatic, completes in seconds, uses relatively accessible materials (at least in the elephant’s toothpaste version), and produces results that students remember. The adjustable variables make it a natural fit for inquiry-based learning. Students can test different peroxide concentrations, different catalysts, different amounts of soap, and different container shapes, each time changing one variable and observing how the eruption changes. Varying the catalyst particle size, for instance, is a concrete way to demonstrate how surface area affects reaction rate.3ResearchGate. Observations on Manganese Dioxide As a Catalyst in the Decomposition of Hydrogen Peroxide: A Safer Demonstration
For classroom settings, the manganese dioxide version with moderate peroxide concentrations (around 30% with coarser catalyst particles) strikes a good balance between visual impact and safety. The full-blown devil’s toothpaste setup with concentrated peroxide and dissolved potassium iodide is better suited to outdoor demonstrations by people who understand the hazards and have appropriate protective equipment.
Troubleshooting Common Failures
If your devil’s toothpaste attempt produces a disappointing trickle instead of a dramatic eruption, the problem is almost always one of three things. The most common is using peroxide that is too dilute. Drugstore 3% peroxide will not produce anything close to devil’s toothpaste no matter how much catalyst you add. You need at least 12% for a respectable elephant’s toothpaste and 30% or higher for the devil’s version.
The second common failure is an insufficiently concentrated catalyst solution. Potassium iodide should be dissolved in as little warm water as possible to make a saturated or near-saturated solution. A dilute catalyst solution still works, but the reaction is slower and the foam less dramatic. Some people use dry potassium iodide powder dropped directly into the peroxide, which can work but tends to produce a less uniform reaction because the powder dissolves unevenly.
The third issue is too little soap. Soap is what builds the foam. Without enough of it, the oxygen gas just bubbles through the liquid and escapes. A generous pour of concentrated dish soap, well mixed into the peroxide before adding the catalyst, makes the difference between a fizzy liquid and a foam volcano. If the foam column collapses quickly, adding more soap to the next attempt usually fixes it.
Old hydrogen peroxide is another culprit people overlook. Concentrated peroxide degrades over time, especially if the container has been opened and exposed to light or heat. If your peroxide has been sitting in a garage for a year, its effective concentration may be well below what is printed on the label. Fresh, properly stored peroxide gives the best results.
Hydrogen Peroxide Decomposition in Contexts Beyond Foam
The same fundamental reaction that powers devil’s toothpaste shows up in surprisingly diverse applications. Concentrated hydrogen peroxide has been used as a monopropellant in rocket engines, where its rapid catalytic decomposition produces high-temperature steam and oxygen that generate thrust. The catalytic beds used in those engines face engineering challenges that parallel what happens in a devil’s toothpaste container: managing the heat, ensuring complete decomposition, and controlling the flow of gas.
In environmental chemistry, hydrogen peroxide is used in advanced oxidation processes to break down contaminants in water. The same reactive oxygen species that form during peroxide decomposition can destroy organic pollutants, pharmaceuticals, and industrial chemicals in wastewater. The iron-catalyzed version of this reaction, known as Fenton chemistry, is one of the workhorses of water treatment. The catalytic cycle described earlier, where iron ions shuttle between two oxidation states while breaking down peroxide, is the same chemistry at work in a devil’s toothpaste eruption. In the water treatment application, though, the goal is to produce those reactive intermediates to attack pollutants rather than to generate oxygen gas for visual effect.6International Journal of Chemical Kinetics. Oxygen evolution as a critical test of mechanism in the ferric‐ion catalyzed decomposition of hydrogen peroxide
Even the human body relies on hydrogen peroxide decomposition. White blood cells produce hydrogen peroxide as a weapon against invading bacteria, and the enzyme catalase in your cells breaks it down to prevent damage to your own tissues. The catalase enzyme is, in fact, one of the fastest enzymes known, capable of breaking down millions of peroxide molecules per second. When you use yeast as a catalyst in elephant’s toothpaste, it is the yeast’s own catalase doing the work. Your body runs a version of this reaction constantly, just at concentrations so low that no one’s blood produces a foam column.