If every ballot in US elections was printed with standard ink, it would equate to more water than the average American family uses. Just think about that for a second, how much water do you think your family uses? Thermal printing is a technology that eliminates the need for that much ink.
Estimation of Ink Usages in U.S. Elections
In 2008, voter turnout was at its highest coming in at a little less than 45%. This means roughly 131 million Americans voted. A maximum voter turnout can be estimated using that same percentage. Which means roughly 147 million Americans will vote in the 2020 general election.
According to the United States Geological survey the average person uses 80-100 gallons of water a day. That means the average U.S. family uses between 250-320 gallons of water a day and 1750-2250 gallons of water in a week. For reference, an average-sized pool in the United States would contain 13,500 gallons of water. So in one week, the average US family fills up ~15% of an average-sized pool.
That means all of the ink used to print ballots you could fill up about 20% of an average-sized pool. However, thanks to a really cool material science we can save hundreds of gallons of ink. And you probably use it every day and have no idea.
What are Leuco Dyes?
This really cool materials science innovation is called a leuco dye. Leuco dyes are a specialized type of phase-changing material. They can be incorporated into the bulk of paper during the manufacturing process or coated on top of the paper as secondary processing. Phase-changing materials are a hot area of research that many scientists are looking into for a wide array of applications.
Leuco dyes are a chemical that changes their structure in response to external stimuli. Examples of stimuli include UV, heat, or pH. The way that the leuco dyes respond to the external stimuli is by changing colors. Structurally, the way leuco dyes work is a bond is broken in the chemical structure and it causes the chemical to change from colorless to a specific color.
This color change is a result of a change in the way that light molecules are interacting with the chemical.
How are Leuco Dye Used in Thermal Printing?
When leuco dyes are incorporated into the paper, the paper is referred to as thermochromic or thermally sensitive. These types of paper only work with specific printers. The printers apply a laser to the surface of the paper to generate heat. This heat causes the leuco dyes to undergo their color-changing reactions. This localized application of heat gives you a resulting printed piece of paper.
Today, the widest application of thermal paper is in receipt printing. However, in addition to receipts, there are actually some voting systems currently that leverage this type of printing technology for ballots.
Benefits of Thermal Printing and Leuco Dyes
From the picture, you can see that thermal printers are much more compact and lighter weight than a traditional inkjet printer. This feature can be attributed to the leuco dyes. By removing the need for ink and relying solely on a laser the printer can be much more compact.
Using thermal printing can cut down on the man labor for many business and process that used printers. From keeping track of the ink levels, changing cartridges, cleaning the printer heads, ordering more ink, as well as the footprint necessary for a printer in an office or polling location there is a significant reduction associated with thermal printers.
Drawbacks of Leuco Dyes and Thermal Printing
However, the thermochromic paper and printer are more expensive than a traditional inkjet printer.
Additionally, the transition that the leuco dyes undergo is not permanent so if you check a receipt from years ago there may not be anything on the paper and that is because the dyes have reverted back to their colorless orientation. This reversal of the chemical structures takes a long time and does not pose a risk to short term applications like receipts of ballots for an election.
Let me know in the comments down below if you can think of any cool applications for this thermally responsive paper.