Greetings, fellow agent. Sending covert communications is of utmost importance to any secret agent.
I’m going to show you how to retrofit your inkjet printer to output secret messages that
can only only be revealed by people who have the secret formula, but feel free to share
this information with other trusted maker agents.
Here’s what you’ll need. Besides an inkjet printer, you’ll need a matching color cartridge
that you can crack open.
To do that, you may need a few tools like a clamp, chisel, and a small saw.
You’ll use one of these containers to mix your invisible ink solution, which is made
out of this crystalized lemon. You can find it in many health food stores.
You’ll tape up your cartridge again with electrical tape.
And you’ll use a few drops of iodine tincture to reveal your message.
Let’s get started, agent. The first step is to crack open your ink cartridge.
Clamp it down and saw away at the gap between the lid and the bottom part of the cartridge.
After you’ve sawed away about a quarter of an inch, use a chisel and mallet to pop the lid off.
Use an X-Acto knife to carefully extract the yellow ink sponge. This can get very messy
so wear gloves and protect your workspace.
Clean the sponge under running water until the water runs clear and then leave it to dry.
With four teaspoons of water in a small container, like this film canister, mix 15 packets of
True Lemon crystalized lemon powder.
Regular lemon juice is not strong enough for this hack. This solution is much more concentrated.
The solution must be shaken or stirred, whatever your preference.
Insert the ink sponge into the solution and let it sit for ten minutes.
In the meantime, use a cotton swab to clean out the inside of the ink tank.
Insert the lemon juice saturated sponge back into the ink cartridge.
This can be a bit tricky, even for an advanced agent.
Replace the lid and tape it shut.
Now it’s ready to go back into your printer.
Use any kind of graphics program to print a page of solid yellow.
Keep printing this page until the remaining yellow ink in the cartridge nozzle has been depleted.
Now whatever message you print in yellow will be in invisible ink.
To make the revealing solution, mix a few drops of iodine tincture into some water.
Iodine tincture can be found in the first aid aisle of your drug store. It’s used
as a disinfectant.
Spray the diluted iodine onto the paper to reveal the message.
If you don’t have access to iodine, you can also use a hot iron to reveal the secret message.
Full documentation of this project can be found in MAKE Volume 16 and I will provide
a link to the instructions in the description of this video.
Well, agent, now you’ve been briefed on how to retrofit your inkjet to printer with
invisible ink. Good luck on your next mission.