Understanding Inks and Papers: A Primer

Creativity is allowing yourself to make mistakes. Art is knowing which ones to keep.” – Scott Adams

As printing technology changed paper and ink became more specialized developing it’s own vocabulary but when it comes to fine art inkjet papers here are a few to get you started:

Dye-based inks use a colorant dissolved in a carrier liquid. With pigmented inks, color comes from fine particles that are suspended in the fluid. Pigment inks are resistant to UV light and fade slower than dye inks. Pigment inks are typically more expensive than dye inks and don’t have the brightness and broad color range or gamut that dye inks exhibit. New hybrid inks such as Epson’s UltraChrome HDX inksets are designed to overcome the limitation of traditional pigmented inks.

Metamerism is the matching of the apparent color of objects without matching their spectral power distribution. The term metameric failure is sometimes used to describe situations where two material samples match when viewed under one light source but not another.

Image Science’s Jeremy Daalder explains that bronzing is a phenomenon where, when paper is viewed from an angle, part of the image takes on a green/bronze tone. That happens because of some of the ink laid on the paper is not absorbed into the coating and sits on top of the page.

The coatings applied to photo paper not only affect how ink is absorbed on the surface but also uniformity, color density and dot gain that causes images to appear darker than it’s maker intended. Swellable coatings include synthetic or natural polymers that swell encapsulating colors in the ink that protect it from airborne pollutants. Swellable coatings are most often used with dye inks, because pigment particles are too large to be absorbed into the coating. Swellable coatings provide excellent image quality and rich color but typically are not durable.

Porous coatings aka microporous or nanoporous media are semi-rigid comprised of millions of microscopic particles held together with a chemical binder. When flowing into the spaces between the particles, the surface of the print feels dry to the touch. When used with pigment inks, porous coatings provide a high level of water and fade resistance.

Paper feel and heft is measured in grams per square meter or gsm. More is better than less. Paper thickness is usually measure in mils. Software drivers for some printers show paper thickness settings in millimeters. Because that’s too large a scale to be useful, inkjet paper specs usually are usually described as mil, or thousandths of an inch or sometimes as points or pt, which is the same as mil.

The Photographic Activity Test (PAT) is an International Standard (ISO 14523) that was developed by the Image Permanence Institute. The test takes between four and six weeks and incubates materials in temperature- and humidity-controlled chambers to simulate aging. PAT predicts potentially harmful interactions between photographs and storage materials such as album pages, covers, and envelopes. The test is also used to test the components of storage materials such adhesives, inks, paints, labels, and tape.

More on ink-jet printers next Thursday.

Author: Joe Farace

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