After watching The Killing Joke over the weekend, it dawned on me I have no idea what chemicals The Joker fell into.

Do we know what chemicals were in that vat?

And for bonus points, has anyone in the DC universe ever attempted to recreate that accident, and produce another Joker?

  • 3
    – Valorum
    Commented Aug 2, 2016 at 8:11
  • 3
    Sorry, are we talking about real world chemicals or imaginarium?
    – Broklynite
    Commented Aug 2, 2016 at 10:27
  • 1
    The chemical composition of SmileX is proprietary.
    – Mazura
    Commented Aug 3, 2016 at 21:36
  • 2
    “has anyone in the DC universe ever attempted to recreate that accident, and produce another Joker?” — perhaps two people have successfully done that! Commented Aug 17, 2016 at 10:13

3 Answers 3


New Answer:

Update: Batman: Funny Bones gives the exact chemical make-up.

Joker's chemicals

Batman: I know its components by heart. The whole list.

Eleven percent sodium hydroxide. Thirty-four percent sulfuric acid. Five percent chromium solution. Zinc sulfide, doped with copper, which gives it its green glow.

Secret ingredient?

Batman also states that he is unable to find anything else in the mixture.

Original Answer.

We don't know

The specific chemical(s) have not been given. Here's what the chemicals have been referred to over the years.

  • Unspecified chemical waste from a playing card factory

This origin is shown in Detective Comics #168, Batman and Robin: The Man Behind the Red Hood? and The Untold Legends of Batman, as well as the Who's Who in DC Universe character guide.

Joker origin 1

Joker origin 2

Joker origin 3

Joker origin 4

Alan Moore, the writer of The Killing Joke, stated that he specifically set out not to contradict that origin.

And the Joker’s origin? Had he had one before that?

Moore: He’d got a kind of muddy kind of origin. They’d said that he’d been the leader of a criminal gang called the Red Hood Mob and that while trying to escape from Batman he’d swum across this river of chemicals.

And that was about it?

Moore: That was about it and this was from a story from, like, the late ’50s or something and so I thought “Okay, I won’t contradict that,” because I kind of believe in working by the rules of the material as it already exists but I can put a lot of spin on that.

Joker origin 5

Batman #451 brings The Killing Joke's origin into the mainstream canon.

Joker origin 6

  • Unspecified acid

Legends of the Dark Knight #50 changes it to "an acid bath at the chemical refinery."

Joker origin 7

  • Unspecified chemicals used for antiseptic drugs

Batman: Confidential #9 further changes his origin by having the Joker doused in chemicals used for antiseptic drugs. Examples of which can be seen here.

Joker origin 8

  • Chemical waste again? Maybe?

The Origin of the Joker goes back to the unspecified chemical waste, but states that it's only a possible origin.

Joker origin 9

To answer your other question, yes, the same process can be used on other characters.

For example, Harley Quinn.

Harley Quinn origin

  • 8
    Ah, dumping chemical waste straight into rivers. Good times, those 50's.
    – Rogue Jedi
    Commented Aug 18, 2016 at 3:13
  • 1
    Rivers make bad things go far away... it's sound logic!
    – Daft
    Commented Aug 18, 2016 at 10:03
  • I only noticed the updated answer now... I've added a bounty to the question, I'll award it to you when I can, in 24 hours.
    – Daft
    Commented Nov 11, 2016 at 11:34

I don't think we ever find out the names of the chemicals specifically. As for your second question, no one to my knowledge has tried to create a "second Joker," but the Joker himself (albeit in different universes) has created Harley Quinn and The Creeper by exposing them to the same chemicals.

  • Harley only recently in new52 was exposed to the chemicals, but this is because of bad writers that don't understand the character (her or any other as far as I can tell)... Also Joker Toxin which isn't 1 formula, creates the same effect as what Joker experience but with the added twist of killing the victim. He has made so many variations and Batman has created anti-toxins to all of them that it is certain that the formula is well know for how Joker was made generally.
    – Durakken
    Commented Oct 3, 2016 at 22:44

chlorine bleach. The bleach or acid made his skin white. But it isnt the chlorine that turns hair green. Oxidized metals in the water bind to the protein in the hair shaft and deposit their color. The metal that produces the green tint is copper, which is most commonly found in algicides, though it naturally occurs in some water. Other metals may be present in water that can color your hair, including manganese and iron. Algicides kill algae.


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