Tag Archives: Ink

UV-printed text allows sheets to be reset and re-used 80 different times

A new technology could change how we think about paper and printing — forever. Based on UV-sensitive paint, the method allows paper to be re-used, making it much cheaper and more sustainable than traditional printing.

A sample of the paper with text.
Image credits Wang et al, (2017) American Chemical Society.

So we’ve seen our fair share of creative ink recipes throughout time — some to grow, some to raise awareness, others made from pee. They’re all awesome. But once ink hits the paper, it’s there for good. If you want to print something else, you need a fresh sheet of paper.

Or do you? A joint US-Chinese team has developed a novel nanoparticle coating which can make traditional inks oh-so-last-year. This blue substance can easily be applied to paper — either by spraying or soaking — and changes color when exposed to concentrated ultraviolet (UV) light. If you need to print something else, just heat the sheet to 120 degrees Celsius (248 Fahrenheit) and voila — the ink ‘resets’. As each sheet of paper allows for more than 80 re-writes, the ink could reduce paper usage in the long run, saving a lot of money and a lot of trees in the process.

I’m blue

Treated paper “has the same feel and appearance as conventional paper, but can be printed and erased repeatedly without the need for additional ink” said teammember Yadong Yin from the University of California, Riverside, for Phys.org.

“Our work is believed to have enormous economic and environmental merits to modern society.”

The team combined two kinds of nanoparticles for the ink. The color is created using Prussian blue particles, a pigment which becomes colorless when it gains electrons. The other ingredient is titanium dioxide (TiO2) particles, which catalyze the photochemical reaction between UV rays and the ink — they release the electrons needed for the reaction.

Image credits Wang et al., (2017) American Chemical Society.

What you get is a beautiful blue color that turns colorless under UV rays. So unlike traditional printing methods, this ink prints the blank spaces of the page instead of the words themselves. Alternatively, you can print the letters only and the text will come out white on a blue backdrop.

The print remains stable for at least five days before the page slowly starts fading back to blue, as pigment particles shed the extra electrons. Or you can just heat it up to reset it as fast as you like.

Applying the coat is a quick and cheap process, and the researchers hope this will promote wide-scale use. As each sheet can be used for 80 or more different prints without further costs, it’s easy to see the commercial appeal of the technology.

Add to that the fact that it also reduces paper use and waste, and you get a real winner. In the US, estimates place up to 40% of waste as discarded paper. All this waste translates to added costs for transport, recycling, or disposal. It also fuels the country’s ever-growing need for paper, an industry which consumes around 68 million trees every year and is one of the dirtiest in the country.

Following the paper trail

Yin first unveiled the prototype ink in December 2014. Its first iteration could only sustain 20 printing cycles, and was trickier to apply onto paper than the current material. The team says they improved the stability, ease of application, and lowered production costs over their previous product.

Now, they’re hard at work taking their technology to a printer near you.

“Our immediate next step is to construct a laser printer to work with this rewritable paper to enable fast printing,” Yin told Phys.org.

“We will also look into effective methods for realizing full-colour printing.”

But my question is — can we make tattoos with this ink?

The full paper “Photocatalytic Color Switching of Transition Metal Hexacyanometalate Nanoparticles for High-Performance Light-Printable Rewritable Paper” has been published in the journal Nano Letters.

One of the oldest known New Testament copies could have been written in pee-based ink

Restoration experts have identified the materials that went into making the purple dye of the Codex Purpureus Rossanensis, one of the oldest known New Testament manuscripts, and they aren’t exactly ecclesial: the ink was made from a combination of lichens and fermented urine.

The debate over exactly how the ancient bookmakers, most likely hailing from today’s Syria, crafted the amazing book using the simple tools and limited resources available to them 1,500 years ago has been ever since the manuscript was found.

The beginning of the gospel of Mark in the codex.
Image via wikimedia

“Even though early medieval illuminated manuscripts have been deeply studied from the historical standpoint, they have been rarely fully described in their material composition,” lab director Marina Bicchieri, from the Central Institute for Restoration and Conservation of Archival and Library Heritage (ICRCPAL) in Rome, told Discovery News.

The strikingly beautiful book is usually housed in the Museum of the Diocese in Rossano, a town in southern Italy. The work is 188 pages long, containing the gospels of Matthew and Mark written down in gold and silver ink. Its exact history is unknown, but it’s believed that Italian monks brought the manuscript from Syria. It was re-discovered in 1879 in the Cathedral of Rossano, and since then the debate over how it was written rages on.

Sadly, much of the book has been lost over time, and the book is extremely fragile. Most of it was destroyed in a fire inside the cathedral, and Bicchieri’s team also had to deal with the damage left by earlier restoration efforts. These conducted by an unnamed team around 1917 and irreversibly modified some of the pages.

“Most likely, what we have today represents half of the original book,” museum officials suggest.

The discovery of the purple ink’s materials was made during the book’s restoration by the ICRCPAL. Aiming not to further damage the work, the team only mended a few of its stitches to keep it from falling apart, then used X-rays to examine the composition of the inks in the codex. They compared their findings with dyes recreated in the lab using recipes found in the Stockholm papyrus – a Greek ink recipe book that’s been dated to around 300 AD.

The team reports that the purple dye, thought to have been made out of Murex (a species of sea snail,) was actually produced with orcein, a dye extracted from the lichen Roccella Tinctoria, and sodium carbonate. The latter was obtained from natron — a salt-like material used to mummify bodies in ancient Egypt, Lorenzi explains. But, to bring out the best shade of purple, the dye-making process seems to have involved using fermented urine to mix the compounds.

The pages are dyed with the purple ink.

The pages are dyed with the purple ink.


“Fibre optics reflectance spectra (FORS) showed a perfect match between the purple parchment of the codex and a dye obtained with orcein and an addition of sodium carbonate,” Bicchieri told Rosella Lorenzi at Discovery News.

To you and me this might seem pretty….gross. But in the day it was actually a very practical choice, as urine was the only readily available source of ammonia available 1,500 years ago.

The team is still preparing their findings for publication, and have yet to pass the test of peer-review — but once they do, they could finally end the century long debate around the purple ink.

Why getting a tattoo hurts — the science behind inking

Your leather jacket and motorcycle aren’t enough for you anymore; they fall woefully short of conveying just how much of a badass you really are. This will not do — everyone must see you in all your glory, the world must know. With a spring in your step, you walk into the best tattoo parlor in town, pick out a design that has a dragon with a skull over explosions and roses and chainswords and… OW! Why do tattoos hurt so much!?


Well, it’s because tattoos have to get that ink deep enough that it won’t get washed away but not too deep so it remains visible — the ideal location ends up being right next to your skin’s pain receptors. Given that most modern tattoo artists do this with mechanical tools that push a needle into the skin from 80 to 150 times a second, it’s easy to see how tattooing gets its painful reputation. However, people have endured excruciating pain throughout history to adorn their bodies with ink. So why do we do it? How do we do it? And can we make it hurt less? The short answer to the last question is yes. Here’s the longer answer:

Not just ink

Tattooing is a controversial subject — some are all for it, others consider it an art form to be perfected and some think it’s repulsive. To each his own, but the fact remains that throughout history, tattoos have had (and in some cases still have) deep running cultural and social implications. People around the globe have long marked their bodies to express cultural identity and community status; it is one method to connect to one’s ancestors or gods, to mark rites of passage, or even “wear” a permanent amulet.

The term “tattoo” is believed to originate from the Polynesian “tatau”, meaning “to mark,” and Dictionary.com defines it as being “the act or practice of marking the skin with indelible patterns, pictures, legends, etc., by making punctures in it and inserting pigments.” It’s a simple enough process, but the tattoo’s shapes, colors, and position on the body, taken together often hold an incredibly deep meaning throughout time.

In New Guinea, the swirly tattoos on a Tofi woman’s face detail her family lineage, while in Cambodia monks display religious beliefs etched in ink on their chests. The Japanese Yakuza’s spectacular patterns or the US gang member’s sprawling tattoos can show affiliation, rank, or if the wearer has committed murder. The “Iceman” discovered in the Alps in 1991 was covered in tattoos, 85% of which line up with acupuncture points, says Dr. Lars Kurtak, world-renowned tattoo expert and anthropologist with the Repatriation Office of the National Museum of Natural History.

“He appeared to have terrible arthritis. [The tattoos were] so dark, they seemed to be repeated applications and some of them he could not reach on his own,” he notes.

In some cultures, successfully enduring the excruciating pain and the blood loss of tattooing with primitive tools marks the transition from infancy to manhood and is considered deeply sacred rites, notes Joseph Campbell in his book Primitive Mythology: The Masks of God. So in the end, there are as many meanings to tattoos as there have been human cultures throughout history.

How are they made — and why do they hurt?

Early tattooing involved cutting the skin and rubbing ink in the wound or using needles made of bone or wood to push ink into the tissue; Western civilization’s first recorded encounter with the Polynesian practice of tattooing dates from 1769, when naturalist Joseph Banks traveling the world aboard the British Endeavour witnessed the “extensive adorning” of a 12-year-old girl.

“It was done with a large instrument about 2 inches long containing about 30 teeth,” Banks wrote in his journal. “Every stroke […] drew blood.”

Banks also recounts how the girl wailed and writhed but two women held her down, occasionally beating her, for more than an hour until the tattoo was complete.

Thankfully, tattooing changed since then. Modern tattoo artists use clean, precise units to deposit dye by mechanically driving one or several needles soldered together in and out of the skin, usually from 80 to 150 times a second, like this:


With each prick of the needle, dye gets injected into the skin, and the body’s immune system responds by deploying white cells called macrophages to deal with the threat. Some of the ink gets lost this way, but most don’t — dead macrophages and the ink they didn’t consume is fixed in skin cells named fibroblasts and remains visible through the thin layers of tissue that cover them.

But we know we can get a scratch and not feel any pain or cut our fingers on paper without so much as a blink. So why is tattooing so notoriously painful? Well, it’s all because of where the pigment needs to go to make a tattoo permanent. Let’s look at your skin’s structure to find out why.

Show me some skin!

The skin is the largest and one of the most complex organs in (on?) the body, serving as the soft outer layer of vertebrates; it’s there to protect and delimitate the juicy, fragile “inside” of the organism from the harsh outside.

There are two distinct parts that make up mammalian skin: the epidermis (this is the outer layer of dead keratinocytes that “flakes” off of to be renewed pretty often) together with the more stable dermis (the layer under it that houses all kinds of glands, hair follicles, blood vessels, lymph vessels and sensory cells) forms the cutis. Directly under the cutis lies the subcutis or subcutaneous tissue, where fatty cells are clumped together to protect you from the cold.

The layer where ink needs to be deposited, the dermis, unfortunately also contains receptor cells that send pain signals to the brain to let us know our body is being hurt; it’s not that bad when you prick your toe on a particularly sharp rock, but when your body is being hurt 80 to 150 times a second, they send out a panicked flurry of signals to the brain, making the experience of getting a tattoo rather unpleasant.

On the bright side, since the dermis doesn’t flake off to be renewed like the epidermis, the dye remains embedded in your skin for life.

The inks or dyes themselves have also evolved over time; as a rule of thumb, tattoo ink is made up of two parts: a pigment and a carrier. The pigment is the substance that gives the ink its color, while the carrier is a solvent that ensures the pigment is evenly mixed, protects against pathogens and aids application. Throughout time, water or alcohol have been the most widely used carriers, while glycerine and denatured alcohols have started being used in modern tattooing.

Pigments have been made from, well, mostly anything colorful; traditional colors were made with materials like simple dirt, pen ink (yay, prisons), soot, even blood. Modern pigments are derived from heavy metals, metal oxides, liquid hydrocarbons, or carbon. But be warned: red dyes, in particular, are known to cause allergies and swelling for a few months after getting a tattoo.

One of the most spectacular (read: insane) pigment recipes I’ve come across hails from ancient Rome and calls for Egyptian pine bark, corroded bronze ground in vinegar, and iron sulfate to be mixed with insect eggs, then soaked in water and leek juice. The concoction would be rubbed energetically on fresh wounds made with needles or blades to create the tattoo. It bugged me.

It really bugged me.

Some tattoos hurt and some tattoos really hurt. Here are some tips

Now, getting a tattoo is going to hurt, there’s no way around that. But there are some areas that are more sensitive to pain than others; as an empirical rule, if you’re extremely ticklish in an area, getting tattooed there is probably going to hurt pretty bad. While keeping in mind that everyone has a different threshold for pain, Tattoos-Hurt.com has put together a chart showing how sensitive different areas of the skin are to pain:

I like how they grade things.
Image via tattoos-hurt

Secondly, a lot of people think that getting a tattoo while hammered or after taking painkillers will make it easier to handle the pain; don’t be one of those people. Alcohol is a blood thinner, meaning you will bleed more and the ink won’t take as easily. Your constant drunken movements will also make the process take longer and the end result will be lackluster. Also try to avoid Tylenol, Advil, coffee, and energy drinks before your tattoo session, as they have similar effects.

Drinking water is a good idea, as well-hydrated skin accepts the ink more readily, so start drinking as much water as you need a day or two before. Taking breaks also helps, but try to take them sparingly, as the skin will begin to swell a lot more during your breaks and constant starting and stopping will interrupt a lot of the tattoo process and adrenaline build-up.

So if you’re looking to get a tattoo, either to celebrate your religion or to show off your lineage, or to simply some cool new artwork on your skin, now you know why it has to hurt and how you can make it hurt less; you can also pass the time being thankful you’re not getting crushed bug eggs rubbed into your wounds. Happy inking!