How to make invisible ink for Apple mobile phone information?

Lemon Ink Filter freshly squeezed lemon juice with a strainer, and then dip the lemon juice with a pen tip or a sharpened stick to write. If you want the words written in this ink to reappear, you must carefully heat the words on the radiator. The text is displayed in brown after visualization. Onion ink is made into onion paste Put these pastes into a tea filter and squeeze out the juice with a spoon. Words written in onion ink will turn black when heated. Be careful when making this ink, because it will shed tears. Vinegar ink needs white vinegar. White vinegar itself has no color, and characters written in vinegar ink can be visualized by heating. What is a water script? This secret script doesn't need special ink. You only need to prepare two pieces of white paper, a window glass or a mirror, water and a soft pen. Dip a piece of paper into water, then carefully pick it up and lay it flat on the window glass or mirror. Then cover it with dry white paper and write the words on it with a soft pen. Then tear off this dry white paper, tear it into many pieces and throw it into different waste paper boxes. When the wet white paper dries, the secret information is written. This piece of paper looks empty and not conspicuous at all. In order to disguise it better, you can also write something casually where there is no water character. The recipient only needs to put the letter into the water to read the secret information on it.