Ink that can only be seen with special glasses is a special type of ink that is made visible under specific conditions. These conditions usually include heat, chemical reactions, or exposure to certain wavelengths of light. Invisible ink has been used for centuries to convey secret messages, and it is still popular today in many different applications. For example, spies often write notes with invisible ink that only they can see to communicate important information.
There are a variety of different substances that can act as invisible ink. Some of these inks only become visible when they are heated, while others require a chemical reaction to be made visible. Other types of invisible ink are designed to be seen under specific wavelengths of light. These inks can be used to create invisible barcodes, for example, which are then scanned with a barcode scanner that is sensitive to these wavelengths of light.
The lifespan of invisible ink varies depending on the type and quality of the ink, as well as how it is stored. In general, these inks can last anywhere from a few days to a few years, though it is important to store them properly to preserve their durability.
There are also several different kinds of glasses that can be used to read invisible ink. For example, some glasses are designed to be used with invisible luminous ink, which is commonly used to mark playing cards. This ink is not visible to the naked eye, but it can be viewed with special sunglasses that have red filters in them. These glasses are often sold in stores that specialize in magic products or online.