Photo printing: When paper ain't paper

The market today is filled with many variants of photo paper. What's the difference and how does the media you choose affect your prints?

In the history of communication materials, paper has definitely proven the most popular in terms of writing or drawing. Since AD 105, not much has changed, except that papermakers have constantly developed more and more types of specialty media, such as coated and dyed paper. Hence, the sheets of cellulose pulp produced by different manufacturers aren't always the same.

Photo credit: HP

As discussed in the first part of our series on photo printing, having a great printer with wonderful inks is not the full solution. We judge a product based on its outputs, and prints consist not just of inks but paper as well.

The market today is filled with variants of paper, ranging from archival to watercolour, to photo. Even more confusing are terms used to describe the coatings, such as porous and swellable. Just what does that geek-sounding jargon mean and what does it have to do with you?

Is fading inevitable?
In the photo printing space, the term "fade resistance" applies to the ability of the print outputs to combat fading due to exposure to light or other fade-inducing agents (ozone) in the air. Through their own and independent lab tests, manufacturers often rate the durability of their photos in years. To do so, they determine the types of chemicals and environments that cause the colourants to fade and accelerate the process. The fade-resistant lifetimes of the media are accurate only for light fading as there are currently no standard methods for estimating and accelerating air-induced fade.

Light fading is caused by both visible light and ultraviolet radiation. These agents break up the colourants over time and cause them to lose those bright, saturated colours, leaving photos looking dull and plain.

Air-induced fading occurs when fade agents, such as ozone, get absorbed into the pores of the prints. These agents attack the dyes and cause them to break down, losing the colours. Ever wondered why some of your prints fade even though you've kept them in an album and away from light?

The two main types of photo paper
Premium-grade photo papers from the various manufacturers are generally made from sheets that are similar to the base paper used in traditional silver-halide photographs. This gives your prints the look and feel of traditional photographs, which is important to most people.

The part that differs is the image coating. The type of coating determines the performance of your photographs in terms of air-fade resistance and output print speeds. Printers that output quickly require media that absorbs and dries the ink quickly. This type of media is made with porous coatings and sometimes touted by manufacturers as "instant-dry prints". As the name suggests, the coating consists of fine particles glued together in such a way that there are air spaces or pores in between them. These air spaces are filled with ink, and subsequently, dyes the paper as the water evaporates. However, because of this structure, porous media is especially susceptible to air fade. Canon's Photo Paper Pro and Epson's Semi-gloss photo paper are examples of this type of media.

Stage 1: When inks meet porous media

Stage 2: How the ink dries on the porous coating

Swellable or non-porous media, on the other hand, has consistently demonstrated resistance to air fade. The name comes from the coating's ability to swell to two or three times the original thickness as it absorbs the ink. After the coating has absorbed all the ink, the coating dries and returns to its original thickness while encapsulating the ink. HP's Premium Plus Colorfast paper and Epson's Colorlife paper are examples of such media.

Stage 1: When the inks are introduced to swellable media

Stage 2: The swellable coating reacts with the inks

Stage 3: After dry time

Tips for long-lasting memories
As you may have guessed, there's no getting away from light fading unless you're determined to hide your pictures in a box all through their life -- which pretty much defeats the purpose of having printouts to show off your memorable moments. Resistance to light fading has nothing to do with the various image coatings. In fact, according to Henry Wilhelm (of Wilhelm Imaging Research), coatings do little to affect light stability of the inks and can even harm the stableness.

While manufacturers often test their inks with a variety of media -- sometimes called a "crepe set" in the industry -- performance is generally best with its own premium-quality sheets. Therefore, if you like long-lasting prints, you may have to buy printers based on Epson's pigmented inks or one of HP's 6- or 8-colour units together with the manufacturer's own recommended media. For instance, HP's 5x series of 4-colour solutions last significantly less than the rated 73 years even if used with its premium colourfast paper. This is because it does not make use of the HP58 photo cartridge which consists of a much more stable ink. The same applies for HP's newer Vivera inks. The 4-colour combination lasts 82 years compared to the 108 years that is accomplished with 6- or 8-colour setups.

If you like fast prints, your prints will last up to 27 years -- if you take good care of it. As the paper media is susceptible to air fade, it may be in your best interest to frame your photos up. The glass will aid in reducing the amount of air, and hence the agents that contact the dyes in the pores of the image coating. Also, using porous media on any printer doesn't automatically mean faster speeds, and could even cause more problems with some models. Printers are tweaked with certain ink loads to produce the high chroma required for bright, saturated outputs. As such, using porous paper on an incompatible unit with high ink loads will have the result of photos that take a long time to dry.

Finally, although swellable medias seem to have the upper edge with regard to longevity, there are drawbacks. The manufacturers sing the same wonderful tune for swellable coating. However, they also fail to mention the problem that occurs in high-humidity areas. Because of the media's nature to draw moisture under its coating, this could present some problems with ink loads. HP, on its part, bundles in a "Ziplock" bag for the media to reduce the paper's exposure to moisture.

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Russ posted a comment   

Last year I got a HP 8250 with the six ink cartridges. What a piece of junk. Using the paper that came with the machine the pictures either faded or turned orange within weeks. Then after one packet of paper the machine just said out of paper no matter how full the trays were. Then the paper would not feed so it is now on the shelf with the HP 950 xi. I gave up on that because it has a mind of its own printing in its own time, often hours later the unit prints when we have all gone home.

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