Everybody likes invisible ink, right? Here's a bit of information on using lemon juice - a natural ingredient - as invisible ink, and using it efficiently.
First, you'll need paper. I used "parchment" paper, a textured paper often used for calligraphy. You don't want to use regular notebook or white printing paper. Since lemon juice is a bit yellowish, it will show up clearly against the white. My advice is use something off-white.
You will also need a writing utensil. I picked up this quill pen at a general store.
Then, of course, you'll need your lemon juice! You could squeeze your own lemons, but it's much easier if you go to Dairy Queen and grab a handful of free lemon juice packets.
Next, you will probably want a little bottle or something to store your invisible ink in. I used a small glass bottle. Empty perfume bottles also work well. If you use something such as this glass bottle, you will need a cork. Depending on the size of the bottle neck, you may have to experiment with different corks to make it airtight (or you could just store your lemon juice in a Tupperware container). I used an eraser.*NOTE: I have not yet tested how long lemon juice will keep once it is opened, so I suggest storing it in the refrigerator.
One more thing! Lemon juice invisible ink can only be brought out with heat, so you'll need an iron.
Now, to get started, dip your quill pen or writing utensil (you can use a Q-tip if you want, but the writing will come out clearer with the fine point of a quill) in the lemon juice. Be sure to dip your quill in the ink often. The only down-side to this is the fact that when you're writing, sometimes you may dip your pen and then forget where you wrote your last letter or word. Try tilting your paper sideways for the light to catch on the wetness of the ink. Write a message on your paper, and let it dry thoroughly.
Now for the fun part: revealing your message! Turn your iron onto the highest setting. Once it heats up, begin ironing over your message. This make take several minutes, and you may have to go over it several times until all of your letters are clear.*NOTE: Your paper may warp, especially if you have a steam iron. This is okay.
*WARNING: Irons are HOT!!! As with all household instruments, use with care. Please use adult supervision if you are under the age of 13, and even then I suggest that you be extremely careful. Don't burn your house down; your parents may not be pleased with me if you do so.
Voila'! Here is what your paper should look like. Now take note that this message was revealed within 10 minutes of the ink drying. I am going to conduct experiments on how different periods of time will affect the quality of the ink that shows up in your message. When I do, I will publish a post on this. For example, if you were sending this in the mail to a fellow spy, it will take at least a day to arrive at his or her house, and that may affect your message. Whether or not it has been cold or hot outside, dry or humid, may also affect the ink. I will test this and post on it later.Hope you had fun with your invisible ink messages, and I'll post on other sources of invisible ink in the near future.
