The Secret Behind the Secret Message Egg

Introduction: The Secret Behind the Secret Message Egg

About: I am a paper engineer, writer, maker and chemist wannabe. In addition to pop-up cards I design and build furniture, lights, costumes or whatever I happen to need at the time. Lipstick, a mixing studio, all-pur…

There is a rumor circulating around the internet that one can write an invisible message on the shell of a hard-boiled egg, then peel the egg to reveal the message, black on shiny egg-white.

This sounds REALLY cool so I had to try it.

Did it work?

Read on...

Step 1: The Wisdom of the Internet, Passed Down From One Site to the Next

Internet instructions abound and they boil down to this:

  • Mix alum (a chemical which used to be used in pickling) with vinegar.
  • Write with this mixture on the shell of a hard boiled egg.
  • Peel the egg to reveal the message.

Depending on the source, there are variations: some say boil the egg before writing with alum/vinegar, others say write, then boil.

Here's a sampling of some instructions:

An egg farmer association
A joke and prank website
A food blog
A "science for kids" website
A christian site (to "show how Christ can put messages upon the hearts of His children").
A witchcraft site
A "thrifty fun" site
And of course, it's also on instructables!

Funny thing about these instructions, they use similar language to describe the chemistry which is going on. They all seem quite fond of the verb "to permeate" as in: "The vinegar dissolves the calcium carbonate in the eggshell, allowing the alum to go through (or permeate) the shell and discolor the egg white."

Sounds scientific, doesn't it?

Step 2: Testing, Testing, 1, 2, 3

I couldn't find alum in a grocery store, but I was able to score some in a pharmacy.

I tried everything:

  • I used both ammonium alum and aluminum sulfate.
  • I tried applying the “paint” on a raw egg then cooking it as instructed.
  • I tried painting a pre-cooked egg and leaving it overnight.
  • I tried painting a pre-cooked egg and leaving it overnight, then boiling it.

  • I tried pre-treating the eggshell by soaking it in vinegar.

Nothing worked. See that bowl-full of eggs? White as the day they were boiled! Adding insult to injury, the writing was perfectly visible on the egg shell!

Step 3: Peer Review

Turns out I wasn't the only one testing... and it turns out no one who has actually tried this experiment has succeeded.

The New Grandmas tried and failed but challenged others to try and report back if successful. There were no reports of success, in fact no comments at all.

Bizarre Labs notes that this trick does't always work, but that he will report back when he discovers the trick. The page was last updated in 2008. I'm fairly certain "not always" is a euphemism for "never." I wrote the author a while back to check, but never got a reply...

In Prisoners, Lovers, and Spies: The Story of Invisible Ink from Herodotus to al-Qaeda, Kristie Macrakis, gives a little context to this rumor (which apparently originates from a Napolitan nobleman called Della Porta, back in the late 1500s). Kristie and her students were unable to replicate the century-old experiment.

Alexandra S, a 4th grade Canadian student, tried 22 times, failed 22 times, and finally asked for online help. The "scientist" who responded to her linked to the poorly researched ehow article. Alexandra, I feel for you!

UPDATE April 2016: And here's another exhaustively researched historical debunking I just found by Craig Matsuoka on the GeniiForum.

I know all those bloggers out there writing with so much authority about "permeating the shell"! They were the annoying kids who in school would hog discussions even though they had never bothered to read the book.

Step 4: Conclusion

This is a fraud dating back hundreds of years, given new life by lazy writers, attention grabbers, and the echo chamber that is the internet. I even glimpsed one on a trailer for the TV show about spies in the American Revolution, TURN.

I do think the tide might be turning though... a couple years ago there was a video all over the internet with a cheesy scratchy film effect, supposedly showing the trick in action, but it has since been pulled from YouTube. It has therefor also disappeared from all the sites which linked to it (including loup226's tutorial), but I did manage to find it here.

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    7 Discussions


    1 year ago

    Hey, I think you got something wrong here

    To do this correctly plant pigments are combined with alum powder and vinegar.

    You used alum powder and vinegar with no pigment. I guess you somehow thought that a white powder would show up on a white egg. Even if the vinegar/alum mixture was penetrating the egg, it would be impossible to tell since the egg is, well,

    You then go along to call this a widely-perpetrated, centuries-old hoax. As CarlS119 (in this exact thread) and many other sources only one Google away show us, this does in fact work.
    Hope I helped!


    2 years ago

    Yes, this does indeed work. Once you boil the egg, let it cool. The shell of the egg, though seemingly non-pourous actually is. With a fine-tipped brush, paint your message on the hard shell of the the boiled egg. Gently heat it with a candle, or a heat-gun. You MUST heat it in such a way for the alum to soak through the fine pores of the shell. This takes time, perhaps 15m, periodic heating and cooling. Wipe the alum from the egg. Make sure there is no residue on the shell and allow to cool. Once the egg is cracked and peeled, and the boiled egg white isn't torn/destroyed, there will be a faint brownish message upon the egg white. TRUTH!


    Reply 2 years ago

    Sorry, I didn't see this comment till now -- but really? Did you try this yourself with success, or did you just read about it? If you did it yourself, did you make a video or take pictures? I'd love to be proven wrong...


    5 years ago on Introduction

    when i went to the international spy museum the talks bout the egg thing too


    Reply 5 years ago on Introduction

    What did they say? That this was done, or that this is a myth?


    Reply 5 years ago on Introduction

    I believe it was really done though i am not sure