The Mindreading Egg (Long Post)

Discuss the historical aspects of magic, including memories, or favorite stories.

Postby Craig Matsuoka » 04/12/02 04:53 PM

I pass by many men, who have written wonders to be delivered to posterity, promising golden mountains, yet write otherwise then they thought. - Giambattista Della Porta (1558)

In Donato Coluccis eggcellent new encyclopedia (sorry about thatI couldnt resist), Stephen Minch included a brief article on the infamous egg-writing trick. If you havent read this book yet, you should. It deserves the Pulletzer Prize (sorry again). Here are some additional historical and technical details you might find of interest.

In my research for the encyclopedia article, I unearthed an interesting new reference. It turns out that this idea is actually centuries older than Hunter. Interestingly, what we now regard as an urban legend did not begin its life as a supposed conjuring tool or leisurely amusement. It was meant to be a way to hide secret messages from the Papal Inquisition. Or so the story goes.

It was during this embryonic (and religiously suppressed) age of scientific thought, that a gentleman by the name of Giambattista della Porta published a fascinating book in 1558 entitled Magia Naturalis (Natural Magick). His work was later translated to English and expanded to twenty books, the sixteenth of which contains a description of the secret egg-writing.

Porta was a truly fascinating individual and lived a very colorful life (much of the color may have been generated by Porta himself, though). He was once called before the Inquisition and censured. In 1592 the Pope banned him from publishing any scientific or philosophic works, but the ban was lifted six years later. An enthusiastic debunker of charlatans and defender of reason, he formed what is believed to be the first modern scientific society, Otiosi (i.e., Men of Leisure).

Theres much more to his story than I can cover here, so I highly recommend that you visit Scott Lincoln "Omar" Davis website, where youll find nearly the entire text of Portas work as well as some interesting biographical information posted for online viewing:

Biography: ... html#price

Natural Magick Index:

Also, Derek J. Price (Smithsonian Institution) wrote an insightful appraisal of Portas writings: ... html#price

Relevant to the matter at hand is Book Sixteen Chapter Four. Here the description given by Porta of the egg writing process is much more complex than the one circulated by modern folklore. It is notable that the technique could be centuries older than Porta, as he himself attributes the trick to a certain Africanus - the identity of which is uncertain. It could be any number of people so designated during the period. Perhaps Roman general Publius Cornelius Scipio Aemilianus Africanus Numantinus (called Scipio Africanus Minor, c.184-129 BC) or Sextus Julius? Who knows?

In his sixteenth book entitled "If Invisible Writing." ("Wherein are handled secret and undiscovered Notes."), he details a myriad of techniques used to accomplish what could be considered today as Steganography the art of hiding or disguising secret information. An excerpt from chapter four is reproduced below:

"How you may write in an Egg.

Because when prisons are shut, Eggs are not stopped by the Papal Inquisition, and no fraud is suspected to be in them, I will show you how letters may be writ on the upper shell and white of an Egg also. For example,

That letters may be seen upon the white.

Yellow, and better when the Egg is boiled. Boil an Egg hard and roll it in Wax, and engrave the letters on the Wax with an Iron point, that the marks may lie open. Put this Egg into Liquor with Alom and Galls powdered. Then put it into sharp Vinegar, and they will penetrate, and taking off the shells, you shall see them in the white of the Egg. Africanus teaches it thus. Grind Galls and Alom with Vinegar, till they be as thick as ink. With this write what you will on an Egg, and when the writing is dried in the Sun, put it into sharp Pickle. Dry it, boil it, and take off the shell, and you shall read the writing. I put it into Vinegar, and could do nothing of it. Perhaps, he means by Pickle, Capital Lees. The cause is this. The Eggshell' is porous, and has large holes, which is plain. For being set to the fire, it will sweat, and water will come forth. And looking at it against the light, it will show clear. So then, Vinegar being subtle, penetrates by the pores, and makes the shell tender. And when it is mingled with the Alom and Galls, it carries their substance with it, and makes them appear on the white. And when it is put into cold water, it is condensed, and comes to be hard as it was. But observe, it must not stay long in Vinegar. For that will eat off all the shell, and will leave the Egg bare, having nothing but a thin skin to cover it. And if you put that into cold water, the shell will not come again. If you will know,"

Portas Egg Writing instructions: ... ml#bkXVIIV

Heres the bad news. Even after obtaining the required materials from a company specializing in historical ink supplies, I have been unsuccessful in getting this to work. Basically, I dissolved some drugstore alum (aluminum ammonium sulfate) in water with a little ethyl alcohol, and then added some gallnuts (i.e. oak apples), which I crushed to a fine powder with a mortar and pestle.

I rolled the egg in some melted wax and inscribed the word 4H all the way down to the surface of the shell. Then I placed it into the alum and galls solution for about two hours and put it into vinegar as instructed. After the messy boil of wax removal, I unshelled the egg only to see nothing on the white. I expected this, since I had previously unshelled another egg and placed a few drops of the alum/gall solution onto the exposed white just to see if anything would happen. Two hours later, pale yellowish stains showed up where the droplets sat, but nothing remarkable or encouraging.

Its quite ironic that this irreproducible experiment issues from a man who wrote the following words in his preface to the book:

Many men have written what they never saw, nor did they know the Simples that were the ingredients, but they set them down from other men's traditions, by ignorance and importunate desire to add something, so errors are propagated by succession and at last grow infinite, that not so much as the prints of the former remain. That not only the experiment will be difficult, but also a man can hardly read them without laughter. Moreover, I pass by many men, who have written wonders to be delivered to posterity, promising golden mountains, yet write otherwise then they thought. Hence most ingenious men, and desirous to learn, are detained for a very long time (and when they despair of obtaining what they seek for, they find that they spend their time, pains, and charge in vain) and so driven to desperation, they are forced to repent by leisure; others grown wise by other men's harms, learn to hate those things before they know them.

Describes my feelings to a T. Yet, in the same preface, he cautions and encourages the reader that he may have purposely obscured his text in some places. So, according to him, just because we cant make the instructions work, doesnt mean they cant be done. Whether this warning applies to the egg writing we may never know:

I did not think fit to omit anything by erring honestly, or following the best leaders, but such as are magnificent and most excellent, I have veiled by the artifice of words, by transposition and depressions of them; and such things as are hurtful and mischievous, I have written obscurely; yet not so, but that an ingenious reader may unfold it, and the with of one that will thoroughly search may comprehend it.

Wherefore, studious readers, accept my long labors, that cost me much study, travel, expense, and much inconvenience, with the same mind that I publish them; and remove all blindness and malice, which are wont to dazzle the sight of the mind, and hinder the truth; weigh these things with a right judgment, when you try what I have written, for finding both truth and profit, you will think better of my pains. Yet I am assured there will be many ignorant people, void of all serious matters, that will hate and envy these things and will rashly pronounce, that some of these experiments are not only false, but impossible to be done; and while they strive by arguments and vain disputes, to overthrow the truth, they betray their own ignorance; Such men, as vile, are to be driven from the limits of our NATURAL MAGICK

Link to preface:

Here are Stephens thoughts to me on the matter:

The problem with Porta's description is, like a good conspiracy theory, it contains enough tantalizing truth in it to make it credible, although in fact it may fail to stand up to analysis. But it is tempting to always think that, if I do this little thing differently it will workPorta obviously believes the method of writing through the shell is not limited to one acid or dying agent. Besides vinegar, he mentions the use of a vitriol solution and limewater. And besides alum and galls, which produce yellow, he mentions galls and wine, as well as brasil, which is a common red dye used at the time. If Porta, as you suggest, is obscuring the real secret (Perhaps because of its stated use for sneaking messages into Inquisition prisons, although this sounds rather apocryphal), it may be hidden in some recombination of these acids and dies. And it might just as possibly be a myth. Porta would not be the only author of the period to make the claim of having examined everything he wrote about, sifting truth from myth. Very similar statements are found in Prevost and others, and none seems to have been completely safe from misinformation, despite an admirable skepticism. However, Porta's debunking of Africanus certainly lends an air of believability to his statements.

At this point, despite my own results, I still didnt know what to conclude about Portas method. Perhaps the description was purposely miswritten, or maybe Im just not doing it correctly. Likely, Stephen Minchs insightful comment to me is closer to the truth I fell victim to the seductive allure of wishful thinking. Surely this information would have been circulated among his many associates and tested. He was a proud man, well respected by his science-minded peers. So, he had much to lose in the way of ridicule by publishing nonsense. On the other hand, he was also known for embellishing the truth when it made him look good. His period was also notorious for propogating falsehood under the banner of science. Notwithstanding this information, Im still reluctant to call him a bald-faced liar. For now, Ill just say that the trick didnt work when I tried it, and leave it at that.

Anyway, Im aware of Sid Fleischmans article and alternate modus, but it sure would be astonishing to let the spectator crack the egg himself wouldnt it? To this end, I attempted to flesh out an alternate procedure for replicating Portas work (or should I say effect?) using food coloring and DidiSeven or some other oxygen bleach. Basically, a character is written on the surface of the eggshell with undiluted food coloring and left there for an hour or so. Then a solution of DidiSeven is used to bleach the ink from only the surface of the shell leaving the interior untouched. In my initial tests, the food coloring was capable of passing quickly only through the shell pores, so the lettering appeared a little spotty or even blotchy at times. Next, I checked to see if presoaking the shell in vinegar would help at all. It didnt.

After all this experimentation, the results are both encouraging and disappointing at the same time. It appears that Porta's method remains unworkable as written. Without having him around to tell us what we're doing wrong, I'm afraid this particular "golden mountain" will remain as elusive and open to conjecture (and ridicule) as it ever was.

On the other hand, it's quite likely others may have envisioned alternate methods in the centuries after he penned those cryptic passages. Perhaps others have employed a solution of Iron Alum and vinegar without the galls. If Wasshuber's experiments with this approach are any indication, credit for the first workable method of egg writing may have to go to someone after Porta. Whatever the case may be, Wasshuber's approach is most certainly not the one Porta took, since mixing Iron Alum and galls (tannic acid) together would make black ink. Obviously, this would render the solution useless for our purpose. I've confirmed this through personal hands-on experimentation. Its worth mentioning that in the centuries leading up to the widespread use of synthetic pigments, indelible black ink (gall ink) was manufactured by mixing galls with an iron salt such as Iron(II)Sulfate. Indeed, it is the reaction of galls with the elemental Iron that imparts to the ink its black color. So Porta must have been using some other form of alum such as Aluminum Ammonium Sulfate - another common compound both in his day and ours.

So far, I've achieved partial success with my alternate method in that the character appears stippled on the white. This is because the shell is not uniformly porous, as one would be led to believe. It has thousands of tiny, randomly spaced pores in it. Each pore is literally a hole taking a straight path through the shell. Naturally, this makes it difficult, if not impossible for the dye to get inside evenly.

Hence, the egg must be freshly boiled so its interior and pores are saturated with water. Old dried out eggs won't work as well, if at all. The dye must also be slightly diluted. Having water present in both egg and dye improves the capillary action necessary for the dye to make its way through the microscopic shell pores. High water content is also critical once the dye gets through, since the moisture will encourage the dye to spread out when it reaches the surface of the membrane and white. This permits the dye spots on the white to blend together and form a more uniform, connected, and essentially legible pattern.

Once the white has been dyed, rinse the egg off with water and use DidiSeven or some other type of bleach to fade the ink on the shell exterior. Blue food coloring is preferred since I've found that red doesn't bleach out as well. The dye won't fade completely, but just enough to permit whiting out of the stain with a matte-finish white paint. I'm going to see if I can get a hold of some Acid Blue 93 (i.e. Methyl Blue) to use instead of food coloring. This is the same type of dye used to make children's erasable marking pens.

My conclusion regarding Porta's writings, at least for time being, would be a qualified "no can do". I've tried just about every combination and concentration of ingredients but still no cigar. Until someone proves otherwise, the original recipe simply will not work. While, one can speculate on Porta's veracity in this case, I won't go so far as to the say his concept is utterly impossible. As Minch already commented in his encyclopedia article, his ideas are not without a certain degree of technical merit.

On a final note, I'm afraid I wasn't able to shed any confirming light on the identity of Africanus as mentioned in Porta's writings. Bill Kalush suggested it may have been Julius Africanus and it may very well be so. His "Kestoi" (or Cesti), which has been attributed to Sextus Julius, seems to be the kind of stuff alchemists of Porta's day would have enjoyed reading. Sadly, we may never be able to read any of it as apparently only tiny fragments of it still exist. I don't think his "Chronicon" would apply here since it was a biblical timeline rather than an alchemical work. We could examine his letter to Origen, but that too is bible oriented. The only source of information on Julius Africanus' "Cesti" is a long out of print French title by Vieillefond (1970). Copies of which are nigh impossible to obtain

I hope youll find this historical information of some use.

BTW, heres anything and everything you never wanted to know about the humble egg from the American Egg Board: (There could be some useful magic to be found in a blood spotted egg. Hmm)

And heres an electron micrograph of an actual eggshell pore. The guy who took the micrograph is Jim Ekstrom, a teacher:

His main page is:
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Postby CHRIS » 04/12/02 07:08 PM


very interesting post - and most likely the longest post on the Genii form - certainly the longest I have seen here. Your bleach idea is an interesting one.

A few comments. I am not sure if Minch mentions this in the Egg book, but my research among egg farmers yielded the information that eggs are treated with a mineral oil to close the pores. This keeps them longer fresh and sanitary. Bacterias and germs can penetrate these pores. This means that the pores are also closed for any ink which we want to pass through the shell. Cooking or other treatments can only partially remove this oil, if at all. So my question would be, have you tried your experiments with eggs directly from the hen, untreated in any way, just washed with plain water? Or are you using supermarket eggs.

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Postby Richard Kaufman » 04/12/02 07:34 PM

I can only imagine the look on a spectator's face upon peeling off an eggshell and discovering writing on the egg. What a stupendous surprise that must be.
A great post!!! Now let's find out how to make it work.
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Postby Craig Matsuoka » 04/12/02 08:47 PM


Yes, Stephen included your observation about modern day processing of eggs. The experiments I conducted utilized both mainland and locally produced eggs. They were thoroughly washed with various agents like Dawn dishwashing detergent, citrus cleaners, surgical hand soaps, dry cleaning solution, spot remover, tartar control toothpaste...hey, you name it - I've tried it.

You should've been there to see it. The stridor of wet scrubbing drowning out the incredulous murmuring above my kitchen sink: "I'm scrubbing an egg with toothpaste. I AM SCRUBBING...AN EGG...WITH TOOTHPASTE!" Oh well, it's all in the name of science. Yeah, that'll be my story. It's all in the name of science.

Haven't gotten around to trying the stunt with eggs fresh from the hen, but Mike Caveney, I'm told, wants to try this with one from his pet chicken. Poor lil thing! But it's all in the name of science.

...I hate science
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Postby Matthew Field » 04/13/02 02:58 PM

Craig Matsuoka wrote: "It was during this embryonic (and religiously suppressed) age of scientific thought. . ."

Trying to sneak that "embryonic" by us, huh Craig?

I had the pleasure of working on the Colucci Egg Encyclopedia and thought I'd never want to read another word about the things, but I really enjoyed your post.

Thanks, Craig.

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Postby Guest » 04/15/02 05:32 AM

Hi Craig,

First my congratulations for this fascinating report. I share a lot of your experience, my radiator saw a lot of eggs drying with vinegar inc on it. And i understand a man, that writes the words "i hat science" after all this without believing him.
Since three years, allways some weeks before the easter hollidays, i tried to do that stunt. I used eggs from the tyrolean hen without any oil on the shelf. I tried to do the acid ink method as well as the wax engraving, both with many different chemical variations and concentrations. My biggest success was a brown spot on the white. So i gave it up, but still dream of it.
To the ones who never give up: I have an additional challenge to the trick. Because, after taking off the sell and reading the "Happy Easter"-Message you should be able to EAT the egg! So no bleaches or aluminium salt allowed!
And another aspect: I don`t think it makes any difference if you take eggs with white or eggs with brown colour. But who knows...

Postby Craig Matsuoka » 04/15/02 12:00 PM


No, it doesn't make a difference if you use brown or white eggs. I tested both. But brown eggs and food coloring could offer a possible workaround to the chemical bleaching.

Instead of bleaching a white egg, use a brown egg and write with brown food coloring. That way, you can just wash the shell with dishwashing soap afterward. Haven't tried that yet. It's only an idea.

For anyone wanting to try the food coloring idea, I don't think the best results are to be had with long sentences or even words. A single large character or geometric shape would probably show up better on the white, due to the stippling effect I mentioned in my initial post.

Or you might not need to have a discernible character at all to generate a mild degree of astonishment. Even an illegible splotch of color on the white could be an adequate revelation of a "freely" selected color.
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Postby Guest » 04/16/02 01:11 PM

What a brilliant essay! Thank you so much Craig for sharing both your scholarship and your research. I enjoyed reading it very much.

Robin Robertson

Postby Frank Yuen » 04/16/02 04:25 PM

Wasn't there a big write up about this effect recently (within the last year) in one of the magazines? I seem to recall reading about the different frustrations in trying to get this effect to work.

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Postby Craig Matsuoka » 04/16/02 05:01 PM

Hi Frank,

Haven't seen you since the video project. Hope to run into you IRL one of these days.

MAGIC magazine ran two articles by Sid Fleischman a while back. The first was "Magic's Second Most Notorious Trick" (December 2000?).

I also seem to remember that it generated many letters to the editor, leading to a followup article a few months later. It had a box describing a needle-prick idea Billy McComb heard about.

I'm away from my library at the moment, but when I get home I'll look them up for you if you haven't already.
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Postby Guest » 09/11/02 11:34 AM


I cannot recal how I done this. But I have successfully written on the inside of an egg!!!

I was in school, at the time, and was an experiment from one of the science books.

I do rember that I didn't wish to eat it afterwards!

and another experiment I recall was a solution that would turn the shell of an egg into a rubbery type mass??? I don't remember if it would drie back hard as before or not? But if It did a square egg would be a very novel thing indeed! Not to mention a shelled egg in a bottle???

I will work my two braincells and see if I can recreate the writings.

(memory just kicked in :) )

My father bought me a chemical kit and I believe the solution was similar to 'invisible ink' if that helps....

Now I'll have to buy another kit :)

If I find the formula I'll share it with you guys!


Timothy Laws

Postby Guest » 09/11/02 12:06 PM


<><><><><><><><><><><><><><><><><><><><><><>< ><><>


Dissolve 1/2 ounce of alum into 1/2 pint of vinegar. Dip a fine tipped brush into the solution and write your message on the shell of an egg. Let dry completely; then boil for 15 minutes.

Writing cannot be seen on the shell, but is on the inside of the egg.


<><><><><><><><><><><><><><><><><><><><><><>< ><><>

Gentlemen Enjoy!!!

Timothy Laws

Postby Matthew Field » 09/11/02 12:23 PM

Originally posted by Timotheous:


Dissolve 1/2 ounce of alum into 1/2 pint of vinegar. Dip a fine tipped brush into the solution and write your message on the shell of an egg. Let dry completely; then boil for 15 minutes.

Writing cannot be seen on the shell, but is on the inside of the egg.


That's the old recipe that doesn't work, which Sid Fleischman wrote about in MAGIC magazine.


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Postby Guest » 09/11/02 12:53 PM

Oh ok....

then I shall Eggsperiment :)

sorry bad yolk

Your friend in magic


Postby John Smetana » 09/11/02 07:30 PM

---------------------------------------------------Richard Kaufman wrote:-----------------------------
I can only imagine the look on a spectator's face upon peeling off an eggshell and discovering writing on the egg. What a stupendous surprise that must be.
A great post!!! Now let's find out how to make it work.

If anyone can get this to work..great..But please don't use it to do a card trick.

Best thoughts,
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Postby Guest » 10/26/02 07:31 AM

John... this is a group of "Magicians"... think about what you're saying here... you're just not dealing with reality. They have to turn it into a card trick, it's just their nature. ;)

Postby Steve Hook » 10/26/02 11:57 AM

Craig Matsuoka:

I'm surprised you didn't mention this at lunch in July.

Thanks for the continued great posts!

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