What Are Solvent Inks?
The term solvent inks refers to printer inks made using various kinds of solvents, also known as volatile organic compounds that are often oil-based liquids. These inks are primarily used for different types of commercial ink-jet printers, while office and personal ink-jet printers commonly use aqueous ink that is water-based. Unlike aqueous ink, solvent ink can be used to print directly on plastic, vinyl, and other non-absorbent materials. Solvent ink is most commonly used to print items such as signs and banners used outdoors and has to be highly resistant to damage and fading caused by weather, scratching and ultraviolet radiation. There are two main types of solvent inks: hard solvent inks which dry quickly and are very durable, and eco-solvent inks that dry more slowly and are somewhat less durable but also give off less hazardous fumes while drying.
Solvent ink is made with pigment, which provides the color; resin, which makes the color stick to the surface the ink is applied to; and a carrier fluid which keeps the pigment and resin in a liquid state until the ink is applied by an ink-jet printer. Different solvent inks use different kinds of solvents as carrier fluids. The choice of solvent determines if the ink is an eco-solvent ink or a hard ink. Once the ink has been applied by the printer, the carrier fluid evaporates in the drying process.
All types of solvent ink produce some fumes while drying, but eco-solvent ink produces less fumes. For this reason, eco-solvent ink generally does not require special ventilation in the printing area. However, ink-jet printers using eco-solvent ink usually require heaters to make the ink dry properly, something that is not needed for the hard solvent inks. This means that hard solvent ink can be used on many types of surfaces that are sensitive to heat. Hard solvent ink is generally considered the most durable for outdoor use, though the durability of eco-solvent inks is also quite high.
Water-based inks can be used for outdoor purposes, but they are much less durable than solvent inks and require special coatings in order to stick to materials such as vinyl and plastics. Solvent ink bonds to these types of materials much better than water-based ink, because solvent ink is a non-polar substance, just like the plastic or vinyl it is printed on. This shared chemical property is what makes solvent ink able to penetrate and adhere to these non-absorbent surfaces.
"Eco-solvent ink generally does not require special ventilation in the printing area" -- not true, because all ink produces fumes, one way or another and the only safe way to prevent a dangerous level of intoxication over the years is if your production house installs adequate ventilation fans, air-ducts to take the fumes away from working area, and decent humidifiers installed to desaturate the air, because every percentage point you can reduce the toxic fumes adds up huge to your health account.
Remember there is no such thing as zero fumes during the solvent printing process. I've worked over nine years in an eco-solvent printing environment, and good ventilation is definitely a must.
I worked as a graphic designer in an office for many years, and our big printers used solvent ink. The copies of ads that we printed out on paper had to be of good quality, since the sales representatives had to take them out to customers for their approval.
Even right after a piece of paper passed through the printer, I could not smudge the ink, even if I tried. This was great, because I had to quickly paper clip that printed ad to an ad sheet with the customer's information on it and pass it along to the sales rep. All of this provided many opportunities for the ink to get smudged, but it resisted.
It was nice not to have to wash my hands every time I touched a printout. I also loved not having to blow on the paper to dry it before handling it, like I have to do with printouts from my home printer.
I have passed by many outdoor signs and wondered how they kept their color. The sun is a powerful bleacher, yet it could not touch this ink.
Solvent ink is amazing like that. All those political signs you see in people's yards around election time have to be printed with this type of ink, because many of them are in bold reds and blues. It would be embarrassing to the candidate for his sign to fade to pink or purple in the sun.
Also, small businesses often have banners printed with solvent ink. They post these banners out by the road or at the edge of their parking lot to attract business, and the more vivid the ink is, the better the chance of attracting customers.
@orangey03 – You would think because the term “hot off the press” refers to the newspaper that they would use heat to dry their solvent inks, but I learned while working at one that they don't. This is why the ink comes off on your hands when you hold a newspaper.
My boss told me that the paper gets printed so rapidly that there is no time for it to dry. Thousands of sheets get printed each minute, so there is no slow passage under a heat source.
This is why our fingers turn black as we read a newspaper. The solvent ink was rushed out, and unlike the ink on magazines and catalogs, it had no opportunity to air out.
I always wondered why the paper coming out of my printer was warm. Now I know that it was because the solvent ink needed to be dried by heat.
The copy machine works the same way. When I run off dozens of copies of memos, they all come out hot to the touch. Picking them up right after they emerge is like grabbing fresh towels from the dryer.
I'm actually glad my printer and copy machine use solvent ink, because there is just something so comforting about picking up paper hot off the press. The ink never smudges when I touch it accidentally, so I guess this heat and dry process works very well.
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