Have you ever stopped to ask yourself how you would communicate after a zombie apocalypse? I mean, it’s not like you will be using internet, or any electronics devices, in all likelihood. Even if you still have them at your disposal, you may not want to use them. Since every phone conversation and every email message, fb, pinterest, etc. are all being monitored in real time NOW, just imagine what it will be like then.
So, just how would you communicate in such a way as not to give away important information (OpSec)? I honestly do not know; I am hoping to ignite useful discussion on the subject here.
There is no doubt in my mind we may find ourselves “going back to the future”; returning to low-tech methods of getting many things done, including, perhaps, communications.
One of the thoughts I had, of course, is carrier pigeons. An Uncle of mine once kept, bred, and trained pigeons. My Aunt hated them. They stank; they were noisy; they were very time-consuming. They need to eat and they need fresh water, every day. They need cages cleaned out regularly, even though the guano, or poop, or whatever you call it for pigeons, fell through the bottom of the mesh cages. Then you had the reproductive issues – managing your flock so you didn’t end up with more pigeons than you could handle.
On the other hand, I’m told pigeons are quite tasty, and were a common food source during WWII. So, one might argue that one could kill the proverbial two birds with one stone: food source and communications!
Naturally, one would need to learn how to train carriers to use them. I’m guessing that takes a lot of time and hard work. So, we may need less time critical methods.
And what if the messages were “captured”, as so often has happened in the past? So then my mind wandered to invisible inks, a.k.a., sympathetic inks. But, how do you make them? I found the answers in a book titled, “Modern Chemical Magic” by Lippy & Palder; these guys are magicians!
A sympathetic (invisible) ink is one that becomes visible when you apply another type of chemical, or handle it in a certain way. They can either be permanently visible, or only temporarily visible (they will vanish again).
Most such inks look like clear water, and, when dry, become invisible on most soft, white papers.
These guys segregate the secrets by color, so, I’ll just follow their lead.
Today, let’s talk about how to write invisibly with the color, Red. There are a number of ways to do this. Please note that I do not include any warnings or information on these chemicals. Do your homework before messing with any chemical, take prudent precautions, and know what you are doing before you do it (as with anything!).
Red Invisible Ink
(1) 15 grains potassium iodide dissolved in one ounce of distilled water. Sponge over with a solution of 20 grains mercury bichloride dissolved in one ounce water.
Potassium iodide is the potassium salt form of iodide, a naturally occurring substance. Potassium iodide can be used as an expectorant to thin mucus and loosen congestion in your chest and throat. Potassium iodide is used in people with chronic breathing problems that can be complicated by thick mucus in the respiratory tract, such as asthma, chronic bronchitis, or emphysema. There are medical warnings that appear to be for too much of it. See: http://www.drugs.com/mtm/potassium-iodide.html
(2) Weak solution of copper nitrate; when writing is exposed to mild heat, it becomes visible.
Copper(II) nitrate, Cu(NO3)2, is an inorganic compound that forms a blue crystalline solid. Anhydrous copper nitrate forms deep blue-green crystals and sublimes in a vacuum at 150-200 °C
(3) Use a strong alcoholic solution of phenolphthalein, which becomes invisible when dry. To see it, expose to fumes of a strong solution of ammonia. As ammonia fumes evaporate, writing disappears again. If you want to make it “disappear” immediately, breathe on it.
Phenolphthalein is a mild acid that can be used for medical and scientific purposes. When used in medicine, this compound is most commonly recognized as an ingredient in over-the-counter laxatives. In laboratory settings, it is typically used to test the acidity of other substances.
Phenolphthalein is a crystal powder that is usually white but may sometimes have a yellow tinge. It does not typically have a smell or a taste. It may, however, cause coughing or sneezing if it is inhaled.
(4) A weak solution of silver nitrate, when exposed to heat (after drying) crates a rose-red color.
Silver nitrate is used as the starting point for the synthesis of many other silver compounds, as an antiseptic, and as a yellow stain for glass in stained glass. Most preppers are familiar with silver nitrate, as it is a water purifier. It’s not hard to find.
(5) Use 10% solution of potassium ferrocyanide (sounds serious, doesn’t it?!). Apply a 50% solution of iron tincture to produce a red color.
potassium ferrocyanide: noun Chemistry .
a lemon-yellow, crystalline, water-soluble solid, K 4 Fe(CN) 6 ⋅3H 2 O, used chiefly in casehardening alloys having an iron base and in dyeing wool and silk.
Also called yellow prussiate of potash.
Sodium ferrocyanide is the main anti caking agent in salt. Further, it is used in the production of Citric acid and pigments, like Prussian Blue.
(6) Write with an aqueous solution of iron chloride and allow to dry. Then use a solution of sodium sulfocyanide, and the writing will appear, in red. Well, it was a lot more difficult to find a straight description of sodium sulfocyanide, although suppliers are plentiful, especially in bulk; you’ll have to look this one up for yourself.
Blue Invisible Ink
Here are chemicals that will produce a blue tone sympathetic (invisible or disappearing) “ink”:
Cobalt(II) chloride; the name alone suggests the color, doesn’t it?! Vanishes upon cooling; mild heat makes it visible again.
Cobalt chloride is an inorganic compound; it is made up of cobalt and chlorine, and has the chemical formula CoCl2. In chemistry, it is most often referred to as hexahydrate with the chemical structure CoCl2·6H2O. It is commonly used in labs. Hexahydrate has a deep purple color; the anhydrous form has a sky blue tone. Blending these two compounds produces a mauve tone. When ignited, cobalt chloride produces a blue-green flame.
Available at Amazon and at www.grainger.com , among other places.
Write with cobalt nitrate solution, then wet with a weak solution of oxalic acid; a blue color will then appear.
Cobalt(III) nitrate is an inorganic compound – chemical formula Co(NO3)3. You can get this from grainger, also.
An aqueous solution of copper sulfate (cs mixed in water). An aquaeous solution uses water as a solvent. Make visible by sponging with a solution of iron chloride.
Dissolve 15 grains of copper sulfate in one ounce of water. Sponge with a solution of 15 grains of ammonium hydrate in one ounce of water.
A hydrate is a compound formed by the addition of water to another molecule, thus “aquaeous”; as used in chemistry. Hydrates are inorganic salts containing water molecules that form a crystal with the host compound.
If you just want a short cut to writing with ink that disappears until wet, use the chemical bismuth nitrate. Let dry. Upon wetting, the writing becomes visible. The instructions do not tell us whether this is a one time thing, or if it will disappear when dry again, then reappear when wet again.
Or, just use silver nitrate in a weak solution (water), and allow to dry. When exposed to light, the writing will become visible again. DO NOT expose the paper to light until you are ready to read it.
So, what is the “right” way to use sympathetic ink? Well….
Write a letter that won’t interest anyone; leave just the right amount of space between the lines. Now use your sympathetic ink to write between the lines and watch it disappear! Or, write the REAL message on the back of the decoy letter. This is how it was historically done.
I wonder how well it would work to use two different hidden messages, two different chemical inks? One could be the decoy (false) message, perhaps “between the lines” that perhaps becomes visible only when wet, and the other “real” message becomes visible only when subjected to light? Most people aren’t going to be looking for two different “hidden” messages, using very different processes.
How To Make Black Invisible Ink
Here are chemicals that will produce a black color for sympathetic (invisible or disappearing) “ink”:
Write with a solution of one part sulfuric acid mixed with 10 parts water. Writing disappears, but reappears when it is gently heated. Note: this is a dangerous substance. There probably are safer choices than sulfuric acid. Sulfuric acid (sometimes spelled “sulphuric acid”) is highly corrosive as a mineral acid. It has the molecular formula H2SO4. It does have a pungent odor (serves as a good “warning”, sort of like a poisonous plant); it is generally colorless but may have a slightly yellow look when dissolved in aqueous solutions. Some labs dye it dark brown to alert people to “hazard” for this chemical. The historical name of sulfuric acid is oil of vitriol.
Write with a 15% solution of ammonium hyperchlorate. Heat the paper carefully to develop the writing. I am having trouble finding info on ammonium hyperchlorate, so, do your homework and proceed with caution.
Dissolve 20 grains of iron sulfate in one ounce of water. Develop the writing by sponging with a solution of 5 grains of tannic acid dissolved in one ounce of water. Tannic acid should not be confused with tannin, found in both green and black teas. Tannic acid is a specific commercial form of tannin, a type of polyphenol; these two are NOT the same chemical compounds. Commercial tannic acid is generally extracted from certain plants, however, including tara pods, gallnuts, or Sicilian Sumac leaves.
Starch boiled in water will turn black when treated with tincture of iodine. These two are very common, inexpensive, and may be one of your best “hidden” choices – who would put these together as an “OpSec tool”, for example?
Writing with a strong solution of mercurous nitrate then exposing to ammonia fumes will cause black writing to appear. On the other hand, exposure to ammonia fumes might me turn black, as well!
Clearly, if you’re going to experiment with some of these chemicals, you might want to do it outdoors, for your own ease of breathing and ease of mind. And be very careful how you store this stuff!
So, what if you’re not exactly the chemistry/geek type, but you want to try some fun stuff like this? Well, look in your kitchen! Use the juices of some of these food items and apply mild heat to reactivate them, after drying:
Lemon juice/Leek juice/Milk/Buttermilk/onion juice/cabbage juice/artichoke juice/grapefruit juice
Salt Writing: dissolve common table salt (sodium chloride) in water (they do not give ratios). Write with this solution on white paper using a clean pen (I’m sure they were using “nibs” or metal point pens such as one would dip in ink – you can buy them in hobby stores, in the “Italic writing” sections). When the writing is dry, scratch over it with a soft pencil and the words you have written will show up plainly in dark lines.
DO keep in mind that this book was written at a time when paper was simply paper; today, most papers are “specialized” and many have any number of chemical treatments, including intentional chemical coatings. This probably will significantly impact your results. I’m guessing the cheaper paper has fewer chemical treatments – just a hint. Experiment, and have fun along the way!
Lippy and Palder’s book, “Modern Chemical Magic” will also teach you how to write invisibly (sympathetic inks) with the colors green, brown, violet, and yellow. It contains many “magic tricks” using these compounds, such as the trick known as “spirit writing”. The book is paperback, yet, it HAS NO COPYRIGHT – not that I can find, anyway. Can you believe that? It does come with a forward by the famous magician, Harry Blackstone. The authors’ complete names are John D. Lippy, Jr. and Edward L. Palder, though I’ll be surprised if you can the book.
And now that we’ve talked about ways to use “sympathetic” (invisible) inks, what ideas and/or suggestions have you come up with to maintain OpSec in low-tech communications post-IHTF?