Piece of dry fuel (for example, tablets containing methenamine) soak for several minutes with a solution of ammonium nitrate and dry. This operation must be repeated again. In solution pills for a long time can't hold them because they dissolve. With these tablets focus can be bad, so it's best tablets cut cubes.
Now if we set fire to the dried pieces, ammonium nitrate, decomposed with evolution of a large amount of gases, vspuchivajut combustible mixture, turning it into a black snake loose. If this "snake" gently take the head, it can easily be twisted into a spiral.
Be especially careful when you demonstrate this focus. Necessarily the presence of adults.