In the second part of our series we look at why choosing the right paper and ink is important

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Ink for ink-jet printers is not just coloured water and photographic paper bears little relation to the sheets that go into a copier machine. Last time we described the way an ink jet printer lays down millions of microscopic droplets of ink to build the smooth and rich tonal qualities that make a photo-realistic print. The way those drops of ink behave when they crash into the surface of the paper has a big influence on the colour, contrast, tonality and sharpness of the final print.

Ink engineering

Ideally, each droplet of ink should create a well defined spot of the correct size. Drops that overlap should not bleed into each other, changing colour in the process. There should be resistance to chemical reaction with the surface of the paper. The ink also needs to be resistant to fading, both by light energy and chemical agents in the air, like ozone, for example. Batch to batch consistency is essential too. Add to all that the growing expectation of water tolerance and you begin to realise just how complex the engineering of ink jet printer ink is. Do independent third party ink manufacturers have the necessary chemical engineering expertise to produce an alternative ink to that produced by the printer manufacturers? There is plenty of evidence to suggest that many third party inks are inferior, so it's a risk to use them.

I stand by the letter of this conclusion, but it has been pointed out since the initial publication of this article that there are some respected purveyors of specialist inks. The scope of this article doesn't cover this area, but it's worth mentioing. I'm more concerned about cut-price inks sold in bulk to often unsuspecting customers.

Above is an original photo image from the camera. Inset is a magnified portion of the face of the girl to the right.

This print was produced using an Epson printer printing onto HP Premium Plus swellable polymer surface photo paper.
Notice the colour shift and the pronounced dots in the magnified area where the ink has pooled on the surface of the paper.
Needless to say, the Epson printer is designed primarily for use with micro porous papers.
If we'd used an HP printer using swellable polymer paper settings and Epson micro porous paper, the result would also be unsatisfactory.

With the recommended and printer driver supported combination of paper and printer,
using appropriate printer driver settings, the printed result is, this time, better matched with the original image.

But there is more; you can choose between dye-based inks and pigmented inks. The former is formed using relatively small ink molecules that are completely dissolved in the water that is the usual solvent for consumer ink jet printers. Pigmented inks are formed by microscopic lumps of coloured material that are in suspension. It's important that the correct ink type is used with the correct printer model, otherwise the printer could be damaged. We'll cover the pros and cons of pigmented and dye-based inks in a later article.

Photo paper surface types

On the paper side, photo quality ink jet papers have a special surface coating to provide an ideal as possible environment for ink drops to behave at their best. Without these special coatings, the ink flows along the paper fibres by capillary action, causing inconsistencies at the microscopic level that reduce image sharpness, colour accuracy and contrast.

This time plain paper was used. The result is characteristically flat and there is inconsistency in the fine details.

There are two types of photo paper surface. Each is significantly different to the other and it's not usual for photo paper manufacturers to indicate which type they produce. Instead, printer manufacturers rely on users choosing their own matching papers that are natively supported in the printer drivers installed along with the printer.

The most common photo paper surface is known as a micro porous surface type. The ink is absorbed into a spongy surface layer and the water in the ink is dispersed and dries within seconds, so prints emerge from the printer dry to the touch and with a uniform finish. Some papers have a gel-like plastic polymer surface coating that absorbs the ink, sealing it inside the layer in the process, which is good for resistance to airborne attack from nasties like ozone. The polymer surface swells as it absorbs the liquid ink, so it is also known as a swellable polymer paper type.

Both types of paper have pros and cons. Micro porous papers are safe to handle almost immediately after they emerge from the printer and their glossy finish types exhibit a very high shine factor, which is unaffected by the printing process. On the down side, the porous surface doesn't protect against attack by image fading agents in the air. Swellable polymer photo paper needs to be handled with care straight after printing and can take hours to dry completely. The polymer coating is not as resistant to water spillage or physical abrasion compared with micro porous papers and glossy finishes are not as shiny as micro porous papers. They can exhibit less uniform surface shine, too, with unprinted or white areas shinier than areas that have been heavily covered with ink.

Manufacturer or independent photo papers?

There is relatively little risk in damaging your printer through using third party papers though achieving perfect results can be a challenge. This is because the printer needs a 'profile' based on a complex model of the colour characteristics of a given printer, its inks and a specific paper type. By using papers recommended by the printer manufacturer, it's likely that the software installed with your printer, called a printer driver, will contain the correct profiles for the these papers when used with that printer and the manufacturer's recommended inks. Changing just one element will likely detrimentally affect the accuracy of a profile. But it's different with third party papers as profiles for their papers when used with a specific printer and its inks are rarely supplied by the paper manufacturer. This is partly because it's a difficult task to produce profiles for the hundreds of different printer models in use. In a later part of this series we will explore how printer profiles can be custom made so you can obtain optimum results with a wide variety of third party papers.

Notice the neutral grey tone gradation through from black to white in this original printer test image.

In this test print, the paper is not matched to the printer properly, causing the neutral grey to be lost and smooth tonal change becomes less consistent.

Recap

Try it for yourself

Make a photo print, taking care to select the correct printer driver paper type setting for the paper being used. Then print the same picture but deliberately choose the wrong paper type setting and compare the two results. You should see a noticeable difference.

Next time, we take a look at the printer driver software that is crucial to the smooth operation of your ink jet photo printer.

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