Articles

Saving Digital Prints

Jannette Hanna and Daniel Burge

People often ask if digital prints will last longer than the prints they got from their film cameras. This concern is legitimate, given that early home-printed digital images were very likely to fade and/or turn yellow. This question is a difficult one to tackle, because there is no simple answer. The answer at the moment is, “It depends.” While sounding like a dodge, that answer really is an indication that the problems and solutions of digital print permanence aren’t simple. The issue is complex because there are several processes by which prints can be made, and each individual process involves a variety of products of distinctly different qualities.

Most digital prints made at home are inkjet prints, and most digital prints made at a lab are silver-halide prints. There are two other processes that must be mentioned: electrophotographic and thermal dye transfer (also called dye “sub” and D2T2).

The life span and image quality of the traditional photographic print is the yardstick that digital prints now are measured against. Traditional film-based prints are created by a wet-chemical development process involving layers of colored dyes embedded in a paper coating. Many older color photos have faded and yellowed, but new wet-processed photos will last for 50 or even a 100 years if well taken care of.

The real digital printing methods don't involve wet chemistry, which makes maintenance easier and supplies less costly. It is also much friendlier to the environment. Each processing method uses a very different technology, and this results in varying image quality and wide range of potential life spans. Each digital print process is discussed briefly below.

Electrostatic Print Process

Photo-copiers and laser printers use a technology called electrophotography. Electrophotographic prints can be made at home on laser printers or in a commercial facility on electrophotographic presses. Color pigment “toners” are laid down and then fused by heat onto an uncoated paper (see drawing below).

Electrostatic print process

Though these prints can last longer than traditional photo prints both in albums or on display, they have not been as popular for photographs because of their usually poor image quality. This trend is changing, though, as manufacturers of commercial equipment have dramatically improved quality. Home printers have yet to match photo-quality, but they are still very useful for fliers, labels, clip art, and other line- or text-based copies.

Thermal Dye Transfer Process

Thermal dye transfer uses heat to transfer the color dyes from a colored plastic ribbon into a special coating on the print paper (see below).

Thermal dye transfer process

These prints are chemically similar to traditional prints, and they are expected to last just as long when taken care of in preservation-quality scrapbooks and albums and stored in good environments. Unfortunately, when exposed to light (e.g., on display in a picture frame or on a refrigerator) many fade somewhat rapidly and change color to a pinkish hue. These prints are usually the type you get from “instant” kiosks in stores, but they are also made on some small home printers (5"x 7" or less).

Inkjet Process

The most common home digital printing method is inkjet. The primary factors that determine the longevity of inkjet prints are the inks and the papers.

The colorants in the ink can be either pigments or dyes. Printers are designed for use with either pigments or dyes, not both. Which it is depends on the brand and type of printer you choose. In general, pigment inks tend to last longer without fading, but dye inks can produce a larger number of colors, and the colors are brighter.

The next consideration in selecting an inkjet system is the number of ink colors a printer is designed to use. Multi-purpose color printers usually have just four ink colors (cyan, magenta, yellow, and black). These are the typical office/home office printers designed for printing mostly text and graphics. They are not optimized to make pleasing images. Photo-specific printers usually have six or more ink colors. This allows them to improve image quality in the highlight areas.

The final factor in inkjet printing is the paper. This is often referred to by manufacturers as “media”. Typical office copier papers and other non-photo papers do not have the special receiver coatings needed to ensure a high-quality image. When water-based ink is ejected by the printer head onto an uncoated paper, the ink spreads out slightly on the paper’s surface causing feathering and dot gain, both of which reduce image quality. This reduces the printer’s ability to show fine details in the image. Also, the water in the ink can wet the paper, making it wavy or cockled.

Ink on uncoated paper

Ink on coated paper

There are two types of receiver coatings for inkjet photo paper: swellable and porous. Swellable paper absorbs ink into a polymer coating that is sensitive to water. When the wet ink hits the surface of the paper, the receiver coat swells and absorbs the colorants. When the print dries the receiver coat shrinks back down creating a protective layer over the dyes. Porous paper is coated with tiny inorganic particles. The gaps between the particles form thousands of tiny pores sized to accept the dyes or pigments. The inks are pulled down into the porous coating through capillary action. The various ink and paper combinations for inkjet prints have been found to last variable lengths of time, from as little as a few years to over a century. The one ink/paper combination that has been found to have a relatively consistent longer lifespan than traditional images is pigment ink on porous paper.

Inkjet prints should be thoroughly dried before they are placed in a frame or album (especially when using plastic page protectors). It is best to wait at least 24 hours to make sure the print is completely dry. This is particularly important for those who live in humid areas.

It is equally important to pay attention to what surrounds your photos and scrapbooks. If they are exposed to reactive storage materials, there may be irreparable damage. At the very least, when purchasing storage products look for ones that are acid-free, lignin-free (paper only), and PVC-free (plastic only), and ones that pass the PAT (photographic activity test). The safest materials will state that they meet the internationally accepted standard ISO 18902 Imaging materials Imaging materials — Processed photographic films, plates and papers photographic films, plates and papers — Filing enclosures and storage containers enclosures and storage containers.

The most important determinant for the longevity of your digital prints will be the environment that they are stored in — particularly the temperature and humidity. Albums should always be kept cool and dry. Mold can start to grow on many digital prints in very humid environments, just as it does on traditional prints. Heat and humidity can cause inks to bleed or prints to stick to adjacent materials. It is best to keep your items as close as possible to 70° and 40%-50% RH year-round. Avoid attics and basements and closets with exterior walls.

Stored in the dark	Displayed in the light

Use the following guide for print storage:

Store albums in a cool, dry place.
Eliminate pollutant sources (e.g., household chemicals).
Handle with care; cotton gloves help.
Keep safe from flood and fire.
Select safe storage materials.

Use the following guide for print display:

Handle gently.
Don’t display in direct sunlight.
Use glass or clear plastic in the frame to reduce light and pollution damage.
Use safe framing products.