This is not attractive.

Jessica Orwig: No.

It really does look like human fat.

Jones: That's me and my boss opening up a lava lamp.

[glugging]

Oh! Are we getting these noises, guys?

Our goal was simple: to figure out what's inside.

As it turned out, it actually wasn't simple at all.

And that's because companies don't want you to know.

Bryan Katzel: It's a formula that, you know, has been

pretty well-guarded throughout time, you know?

Jones: That's Bryan Katzel, vice president of

product development at Schylling,

the manufacturers of Lava brand lava lamps.

And true to his word, he wouldn't share the full recipe.

But he did reveal some key ingredients.

Katzel: Inside of a lava lamp, you've got wax,

which is mostly paraffin wax.

That's your lava.

Jones: Paraffin wax is a common wax made from petroleum.

You can often find it in candles and cosmetics.

But when we squeezed it in our hands,

it didn't really feel like melted wax at all.

Orwig: It sort of has the consistency of mashed pumpkin.

Jones: And what about all that liquid?

Katzel said it's mostly water.

And since wax doesn't mix with water,

that makes a lot of sense.

But, as you can see, it's not just water.

Yes, that extra coloring is partly for effect,

but it also contains chemicals that prevent fungus

from growing in the bottle.

And, of course, he did leave some things out.

Katzel: You know, there's a little bit of lava magic

that we sprinkle inside there.

But, essentially, it's liquid. It's water and wax.

Jones: That "magic" is actually really important,

because it's what makes lava lamps work the way they do.

Stefano Sacanna: You have these two liquids that are

separate, but now you also want to have this effect

where one of the liquids sort of dance around

and goes up and down.

And that has to do with the density.

Jones: He says the density is everything when it comes

to lava lamps.

When the lamp is off,

the wax is slightly denser than the liquid around it.

And that's why it sits at the bottom.

And when most materials warm up,

they expand and become less dense, or lighter.

That's what causes the wax to rise.

And then, when it reaches the top,

farther from the heat source, it cools, contracts,

gains density, and eventually falls back down.

So what does this have to do with what's inside?

Well, regular wax is normally lighter,

not heavier, than water.

So then what sort of wax is this stuff?

Sacanna: I suspect what you have inside is, in fact,

not just plain wax.

Most likely what you have is a mixture

of wax and some additives.

You add a little bit of this additive

until it just starts to fall down.

And that is when you reach that sweet spot.

And now you can use the temperature to tilt the balance,

either one side or towards the other.

And so I suspect that most of the trademark secret

is what kind of additive you want to add.

Jones: We asked Katzel about this,

and he said at Lava, those additives are

actually in the liquid, not the wax.

Katzel: At the end, you know,

you do a little bit of tweaking to the liquid

to make sure that the wax is more dense

than the liquid.

Jones: We may never know for sure what those

special additives are.

But a study published in 1996 may hold a clue.

The researchers report they found that one lamp

of an unspecified brand contained kerosene,

which Sacanna confirmed could make the liquid less dense.

But whatever those "magical" additives are,

they smelled really bad.

Orwig: Ugh! Smells terrible. Jones: Exactly. Yeah.

This is not, Orwig: Awful!

playing with it is not helping the smell,

as it turns out.

Orwig: This smell is, like, making me nauseous.

Jones: So suffice it to say, we won't be opening

another lamp anytime soon.

And according to the company, neither should you.