How to restore the disappearing handwriting on movie tickets
First, I researched the paper for movie tickets - thermal paper. The basic principle of this thermal paper is chemical reaction. It uses a thin film to separate two colorless reagents for color reaction. When the thermal print head passes through a specific area, the film is scalded and the two substances change color. So we see the handwriting above. However, this reaction is susceptible to other physical and chemical conditions. Once affected, the handwriting disappears.
Factors that affect color response include the following:
(1) Long storage time;
(2) humid environment;
(3) Higher ambient temperature;
(4) Contact with alkaline substances;
On thermal paper, I did some further homework.
The origin of thermal paper: The earliest printing technology was undertaken by thermal paper. The R&D companies were NCR and 3M, which led the era of supermarket cashiers at that time.
In 1965, the Texas company invented the thermal print head, named 700 (silent700), which was widely used in supermarkets in 1969. By the late 1970s and early 1980s, Japanese manufacturers had innovated. By the early 1990s, inkjet printing, laser printing and electronic printing technologies appeared one after another, compressing thermal printing to very limited areas of certification such as supermarket cashiers and bank receipts, but due to its obvious advantages.
Production of thermal paper: It is conceivable that thermal paper is ordinary paper with two layers of "paint" on it and a film in the middle to make it look like a sandwich biscuit. Long, a layer of film is added on the top layer, which increases the cost, also known as the top product of thermal paper. Let's talk about the ingredients of these paints. The two layers separated by the membrane are generally acidic substances and color-developing agents of different colors. For example, some words are black, some are purple, and some are blue. Of course, different developers are different, but almost all of these acidic substances contain something called bisphenol A (BPA).
Printing process: The thermal printer has a simple structure, consisting of a roller and a print head, without ink cartridges. There are many tiny semiconductor elements in the printhead that heat specific areas depending on the text to be printed. This tuned heat has two basic functions: melting the film and allowing the two substances to react quickly and develop color. Driven by rollers, a roll of printing paper is unfolded, and the writing is clearly legible.
Knowing that we already know the rationale here, now we just need to solve the problem.
Why does the handwriting on the tape on the movie ticket disappear more easily?
Because the tape is alkaline and BPA is acidic, even after the reaction, the colored writing will become colorless when it encounters an alkaline substance. If you can stick an acidic film, or a film like a thermal paper interlayer, it may extend the storage time slightly, but the technical difficulty is too great, and due to the flaws of the design itself, it cannot play any fundamental role.
Can you recover lost handwriting? How to do it?
The answer is yes. There are two recovery methods:
1. Work hard on the word itself. For example: directly retrieve the lost handwriting through chemical reaction; or through high-tech image recognition technology, enhance the contrast between the enlarged disappearing handwriting and the surrounding background.
2. Push hard on the surrounding background. The chemical reaction in the character display area has ended and no new reaction will take place. The background material has not reacted yet. If these materials have reacted and are black, then white characters can be displayed.
How to save movie ticket stubs
There is an option to scan or take a photo for the first time; the real thing can be placed in a small dry box, sealed with desiccant, and frozen in the refrigerator. It is estimated that when you are old, the words on it will still be legible. Those small pieces of paper will remind you of your first love, the person you once loved, and the look of your youth.