Why is a raven like a writing desk?
“Have you guessed the riddle yet?” the Hatter said, turning to Alice again.
“No, I give it up,” Alice replied: “what’s the answer?”
“I haven’t the slightest idea,” said the Hatter.
– Lewis Carroll, Alice’s Adventures in Wonderland

In 1865, Lewis Carroll (real name Charles Dodgson) published the novel Alice’s Adventures in Wonderland. The book is absolute literary nonsense, playing on logic with a cast of eccentric characters. The story and its sequel Through the Looking Glass have inspired countless adaptations, many of which contain the Hatter. Even amongst the rest of crazy characters, the Hatter is particularly off-kilter, spouting nonsensical comments and asking unanswerable riddles.

It’s not the Hatter’s fault he was so mad- it was just an occupational hazard.


In the 1800s, hatters- that is, those who made hats- were exposed to mercury, a neurotoxin that affects the nervous system. During the hat-making process, beaver or rabbit pelts were brushed with mercuric nitrate solution. The mercury was used to break down the keratin protein structure in fur. Keratin contains disulfide bridges, covalent bonds between sulfur atoms, giving it extra strength and rigidity. The disulfide bonds were broken with mercury, weakening the overall keratin structure. Breaking down the keratin roughened the fur so that when it was separated from the skin, it would mat together more easily. The resulting mat was then shaped and shrunk using boiling water before it was dried to make dense felt. The hatters could then shape and finish the felt into a hat.

Felting Process – J. Moss Ives

Making felt was often done in a poorly ventilated room to prevent the fur from being blown about. (Remember, this was pre-OSHA and in a time when employees’ health wasn’t high priority.) Because of this, hatters were exposed to vaporized mercury from the felt treatment process. With enough exposure, the hatters could fall victim to mercury poisoning. Symptoms of mercury poisoning are varied, but include headaches, insomnia, emotional changes, tremors, muscle weakness, and mental disturbances. In other words, hatters could become unstable physically and mentally- they could go “mad.”

It may be interesting to note that the design of the Mad Hatter in the 2010 live-action movie Alice in Wonderland may be based on the theory that he suffered from mercury poisoning. Treating the fur with mercuric nitrate was also known as carroting because it would cause fur to turn orange. Perhaps the Mad Hatter’s orange hair was a subtle reference to exposure to mercury.


[I would be remiss to say that “mad hatter disease” isn’t the only theory of where Lewis Carroll may have drawn inspiration for the Hatter character. One popular theory states that the Hatter is based on Theophilius Carter, a furniture dealer who allegedly wore a top hat and invented an “alarm clock bed” that would wake someone up by dumping them on a floor. Carroll and Carter supposedly lived in Oxford at the same time, but there is no hard evidence that they crossed paths. Another possible Hatter inspiration is Thomas Randall, a tailor and hatter (and eventual mayor of Oxford). Alice Liddell, the inspiration for Alice, would visit Randall and take his dog out for walks. Liddell may have talked about Randall to Carroll.]

If you dream of becoming a hatter but don’t want to breathe in mercury vapors, don’t worry- using mercury in felt processing was banned in the U.S. in 1941.

Keep calm and science on.

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