Water

The ink in inkjet cartridges can be as much as 95 percent superpure deionized water. Yet at more than $3 per milliliter, it would be cheaper to print your vacation pics with Dom Perignon.

Butyl urea

Remember how inkjet pages used to curl up? Water in the ink causes the cellulose fibers in paper to swell and breaks the H-bonds between them. As the moisture evaporates, the fibers form new bonds, and as they shrink back to size, the new configuration makes the paper bend. Butyl urea slows the formation of those H-bonds, preventing curl.

Cyclohexanone

This organic solvent helps ink adhere to polymers, making it useful for things like outdoor signs made of PVC. It can also be found in heart-bypass and kidney-dialysis patients: The equipment used to pump blood outside the body leeches this stuff into the circulatory system, and tests show that it may reduce the heart's pumping.

Reactive Red 23 dye

Actually magenta. This copper-containing colorant is also found in tinted contact lenses.

Direct Blue 199 dye

Made of copper phthalocyanine and sulfur. "Direct" dyes can color natural cellulosic fibers like paper, cotton, and hemp without the use of a fixative.

Acid Yellow 23 dye

Known to the FDA as tartrazine, this yellow dye, which is also used in foods, is reported to trigger asthma attacks, hives, and contact dermatitis in some people. So if you print out a picture of a lemon, don't lick it.

Ethoxylated acetylenic diols

Officially called a surfactant, this modifies the surface tension of the water and dyes: Too little tension and the ink will run out of the cartridge; too much and it won't print when it needs to. Manufacturers try to keep the surface tension of the ink droplets to about half that of pure water.

Ethylenediaminetetraacetic acid (EDTA)

That strip of adhesive protecting the print nozzle before you install it is often loaded with metal contaminants. The EDTA, a hydra-headed molecule that forms a cat's cradle of coordinate covalent bonds, traps them so they can't foul the ink or clog the printheads.

Ethylene glycol

Keeps the dyes in solution with the water and slows evaporation, preventing print nozzles from clogging.