(shamelessly stolen from http://www.mud.co.uk/richard/sbos18.htm)
How To Make Invisibility Paint
If you put invisibility paint on anything, it turns it invisible. Here’s how to make invisibility paint:
Start by taking a large tin, which must be able to hold enough paint to fill it. Take one ordinary apple (or, if you don’t have an ordinary apple, a doughnut-shaped one). Chop it up and put it in the tin.
Add a soft nutshell, a silver-looking cobweb, three white onions, a piece of paper with “Deely Bo” written on it, a pinch of September sunlight (or two pinches of August sunlight), and a sugar pencil. Blue sugar pencils are best.
At this point, you should say, “Star of stars, so far and faint, help me with this see-through paint.” You have to say it out loud, no matter how stupid it makes you look, because the paint will know if you haven’t.
Next, you crush a moth and put that in the tin, then add a slug’s eye-stalks, a snake’s skin, a tree, and the sting from a poisonous cat.
And I’m sorry about this, but you also have to add a drop of your own blood. A friend’s blood just won’t do, no matter how much of it you can get.
Three months earlier, you should have ordered from your local blacksmith a small hammer with the metal bit shaped like a pear. Hit the side of the tin seventy-seven times with this hammer. Ignore any grown-ups who complain about the noise.
Lastly, fill the tin to the brim with some nice, fresh milk.
Mix everything together with a large spoon, and bake it for two hours in hot snow.
And that’s all there is to it! Invisibility paint!
Remember, invisibility pain makes things disappear completely. Whatever it gets on will turn invisible straight away. Be careful!
Now you know how to make invisibility paint. I’ll let you figure out how to find the tin once the mixture is ready.