Well, what the main difference between all these types of inkjets boils down to is in each case how the ink they put down dries. And on inkjet printing, that is no small thing.
Aqueous:
Aqueous overall can be thought of as the highest quality type of inkjet. Typically you'll find your highest quality printing done on aqueous printers, and they tend to have the largest color gamuts, and the smallest dot sizes. They're also by far and away the most common inkjets out there; just about every desktop inkjet printer and little photo printer out there is an aqueous printer.
Note that gamut is as much a function of the hardness and smoothness of the final printed surface as it is of ink. So if you're printing on a soft and textured stock on an aqueous machine, you might very well get a smaller gamut than you would on, say, a cast vinyl on a solvent machine. Also one reason aqueous machines tend to have the biggest gamuts in the industry is that you'll find CMYKOGV inskets -- often misleadingly called CMYKRGB by the manufacturers -- in aqueous inksets only.
As you mentioned, these machines run water-based ink. And basically, they typically print into a "receptor coat" that is the top coat of the printing medium. You can loosely think of it as a sponge that holds the ink in place on top of the media. The ink dries initially by filling the receptor coat, and then entirely by "gassing out" of the receptor coat.
Their benefits are mainly image quality, and variety of media on which they can print.
Their downsides are that usually they're not particularly fast, not too durable outdoors, and the media tends to be pretty expensive, as you're buying the media and the receptor coat when you buy most media.
Overall, if you're doing photo-quality or fine art, aqueous is what you need.
Next you have solvent:
Basically solvent ink dries by chemically binding to the printing media, and then by, again, "gassing out" any remaining solvent. The first good news of this process over aqueous is that you don't need a receptor coat to print into, since the ink is binding straight to the media, so solvent media is significantly cheaper than aqueous media.
The first problem you run into is that the gas that gasses out of true hard solvent ink is some pretty noxious stuff. It's not something you want to breathe all day long. Or even for part of the day.
So, the solvent segment is typically broken down into hard solvent, and mild solvent, which is typically called "Eco-Solvent."
Eco-Solvent has the benefit of being able to print on solvent-ink media in smaller work areas -- such as small store-front sign shops -- and without the need for ventilation you have to have with hard solvent printers. Since it's not a highly aggressive solvent, however, it has the disadvantage of not being able to run very fast -- compared to hard solvent; since if you try to lay it down too quickly, you'll find your media rejecting the ink, which leads to mottled-looking prints, particularly in certain solid colors.
Eco-Solvent is also by its nature very prone to "hue shifting" -- called metamerism, somewhat incorrectly, by many -- of grays. This is the phenomenon where you print a color and it looks different under different lighting conditions. Also Eco-solvent has never been able to get -- all things being equal -- a really strong red at resolutions and speeds most printers can make money using.
Of course Correct Color profiles can help tremendously with both these issues, but they are inherent to Eco-solvent printers.
Also of course while Eco-solvent will last long enough outdoors for most applications, it does fade a good deal faster than hard solvent.
Hard solvent on the other hand, typically can produce a better red than Eco-sol; is not as prone to hue-shifting; can run much faster than Eco-sol, and as it is biting the media harder, is less prone to fading outdoors.
But of course you have to deal with ventilation.
UV...
UV printers are basically inkjet printers that use UV ink. Pretty much the same ink as UV silkscreen ink. And they dry the ink by curing it with UV lamps. The lamps are typically mounted to either side of the printhead carriage, so the effect is for all itents-and-purposes instant drying ink.
And because of this, they can pretty much print on anything. If you can get it under the printhead, they'll spray it and cure it.
UV ink is also pretty fade-resistant outdoors. Right up there with hard solvent.
The main downside of UV ink is that UV ink does not like to dry flat against the media. A UV drop, perfectly dried, would stand on the surface of the media like a little cone. For that reason, UV ink tends to be much thicker on the media than solvent; typically does not have as much color gamut as solvent; and while it will dry onto anything,
adhering to anything is sometimes another story.
And, latex...
What latex is is a machine made to print on solvent-ink media, without the solvent.
And the way it does that is by printing -- basically -- inside an oven. It's the heat of the oven that dries the ink. And it works. For certain applications anyway.
What you wind up with is a machine that's pretty comparable to Eco-solvent in terms of performance, at least in terms of types of materials printed and outdoor durability and the like.
But there are some key differences. First is that if latex printers are not very fast -- even slower than Eco-solvent -- and there's no way to speed them up. The ink has to be in the oven for long enough to dry, and also can not be laid down too quickly.
That's too their disadvantage. To their advantage, they're capable of a better red than Eco-solvent, and are not nearly so prone to hue-shift.
Also to their advantage, prints come out of them completely dry. No out-gassing needed. This is a huge deal to vehicle wrappers, as they can go straight from printer to laminator with no out-gassing time needed at all.
To their disadvantage, they print inside an oven. And that means every time you start a print, you need to preheat the oven. Not a big deal if you run long runs. Also they tend to be a pain to load, compared to Eco-sol, and also there are some media they just won't print on at all.
For those reasons, I'd never recommend a latex printer to anyone as their first printer, or their only printer. If you had to run a bunch of small jobs on differing media on one of them, I can see it getting real old, real quick. But as a printer dedicated to nothing but, say, vehicle wraps, I can see them as viable machines.
Mike Adams
Correct Color
