Receipts of all kinds utilise thermal paper, most of which are poor quality. Inferior quality thermal paper is highly susceptible to heat, sunlight, moisture and rough handling, all of which degrades legibility. Thermal paper is not printed on; there is no carbon toner or ink. Images and text are produced when a heated print head comes in contact with the treated paper. There are several techniques that may make faded thermal paper text visible, but because of the dissimilarities in coating properties, results may not be satisfactory on any given paper.
- Skill level:
Things you need
- Laminator pouches
- An iron
- Flatbed scanner
- Nap-free kitchen towel
- Sheet of black construction paper
Take digital photos of the thermal paper. Transfer the digital photos to your computer. Use a photo editing program to manipulate the photo. Adjusting the levels, curves, gamma or contrast can bring out the faded portions of the image. Try the program's "invert" filter to make a negative image of the photo to highlight faded text.
Cut a few pieces from the faded thermal paper to be used as experiments. Cut the samples from a non-critical area, but be sure they contain some text or graphics.
Photocopy one of the cut sample pieces. The faded paper may be legible in the copy. If not, try adjusting the copier settings to darker. Some thermal papers can turn black from the light and heat of the copier, so be sure to use just a small sample of paper.
Place another of the cut samples into a laminator pouch, and run it through the laminator. Because thermal paper is heat sensitive, the laminator's heat will cause a chemical reaction, possibly making the print visible again.
Scan a cut sample of the thermal paper on a flatbed scanner using the colour setting. Cover the thermal paper with a piece of black construction paper. The heat and light from the scanner may activate the chemical process in the thermal paper again. The black paper prevents scattered light from activating non-text areas of the thermal paper.
Place a nap-free (flat, non-fluffy) kitchen towel on an ironing board. Iron another cut paper sample, using a dry iron. Steam will ruin the paper. Depending on the thermal paper coating, the iron's heat may activate the chemical process to make the printing visible.
Blow a sample of the faded paper with a hair dryer, set on low, for a few minutes. The dryer warmth may make any text appear white against a dark background.
Shine a UV (black light) or infrared light onto the thermal paper in a darkened room. UV or infra-red light causes some thermal paper text to glow. If the text appears under the UV light, snap some non-flash digital photographs. Having a friend hold the light makes this easier. As of late 2010, handheld UV lights can be purchased online for under £6.
Tips and warnings
- If you don't have enough faded thermal paper to cut samples, try to find another copy from the same location to experiment with.
- Make copies or take a good digital photo of any important receipts printed on thermal paper shortly after getting them; a faded thermal receipt won't help if needed for a return or warranty.
- Take several photos of the faded thermal paper, using different settings: with flash, without flash, macro mode, with bright light, with low light. Get as close as possible while maintaining focus. Make a copy of each photo before manipulating it, to keep the original pristine.
- Look up "forensic document examiners" in your area to locate a UV or infra-red document scanner if the faded document is critical.
- If you do not have a laminator, many photocopy stores have them for use.
- Free photo editing programs can be found online.
- Try ironing a faded thermal paper only as a last resort. While ironing some thermal papers may prove useful, it can turn some papers entirely black, as heat is what makes text and graphics visible.
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