This is my first instructable and wanted to do something fun. I chose a fun an innovative way of passing notes. I call it "Secret Notes". They're fun for pirate themed birthday parties, treasure hunts, or just a way for you and your friends to write to each other without anyone knowing what it says. I hope you guys like it and make sure to be safe, in my instructable a heat source like fire is needed so make sure you have adult supervision if needed.

Step 1: Materials

- Your choice of white paper, I chose a standard 8.5x11 sheet of paper but any kind will do

- Baking Soda

- Water

- Lighter, Match, Candle, Burner on a stove, or heat lamp. A lighter will work the best and will work the quickest but if needed a match or heat lamp will work too

- Cotton swab, Cotton ball, or Paintbrush

- *Optional* If you want to paper to appear aged, you can soak the paper in tea, or coffee. I will explain how to do that at the end of this Instructable

Step 2: the Invisible Ink

To make the invisible ink solution, you need to mix equal parts water and baking soda. Stir the solution until fully dissolved. *NOTE* Make sure you make enough solution so you will be able to apply a think about of solution on paper.

Step 3: Applying the Solution

Before you start to apply the solution make sure you know if you want to use it on aged paper. If you do start step: 6. Once you have your paper set, use your cotton ball, cotton swab, or paintbrush, to write your secret message. Make sure you write neat and have a dense coat of the solution. Once finished, set aside.

Step 4: Drying

Make sure you leave you secret note enough time to dry. If it's not dry then the secret note will not work when you are trying to read it.

Step 5: Looking at the Secret Note

To see your secret note you have to apply heat. The best ways are with a lighter, or stove top burner but you can use a match or a heat light. When heat is applied to the note, the baking soda/water solution will start to burn and brown. Be careful with the heat, hold the heat source 3-6 inches away from the note. Once legible, move to a different part of the paper and so on.

Step 6: Making the Paper Appear Aged

To make the paper appear aged, you need to soak it in coffee or tea, both work great. Let the paper dry, if you want the note to look more authentic, you can crumple it up. Make sure you crumple it up before you soak the paper or after when dry.