A rather curious news item crossed my desk last week. Apparently, a group known as INGEDE is not at all happy with the contention of another group, DPDA, that it has been successful in deinking inkjet-printed  paper. (Full disclosure: I hate acronyms. And if you do, too, you will be thrilled to know that INGEDE is the  International Association of the Deinking Industry, based in Germany, and DPDA is the Digital Print Deinking Alliance, based in the UK.) The kerfuffle seems to be over which association’s standard should be used to benchmark deinkability. At least I think that is what it is about.  But it got me thinking…how does one get ink out of a sheet of recovered paper anyway? Before it becomes part of a new sheet of paper, recovered paper needs to undergo a number of processes to make it suitable for reuse. First, the paper must be sorted so that no obvious contaminants remain in the recovered paper stream. By contaminants, I am referring to stuff like plastics (can you say, “UV coating”), metal, and that big chunk of cheese, pepperoni and tomato sauce stuck on the lid of last week’s pizza box. The best way to exclude contaminants is to keep them out of the recovered paper stream in the first place. Barring that, contaminated material can be removed from the recycling stream manually at a recycling facility. And some contaminants, such as saddle stitching and the like, can be removed by screens and centrifuges during the re-pulping process. Still, some schmutz will remain in the recycled pulp slurry – mostly ink and glue residues (which, appropriately, are referred to as “stickies”). Stickies cause problems for paper makers because they do what their name suggests – they stick to various parts of paper machines, causing imperfections in the web of paper being formed. Makers of recycled paper get rid of this stuff through a combination of two de-inking processes. A water washing process is used to get rid of small particles of ink. Stickies and larger ink particles are removed through a process called flotation deinking. During flotation deinking, pulp is fed into a large vat called a flotation cell. Air and surfactants are injected into the slurry, causing ink and stickies to break free of the paper fibers and adhere to the air bubbles as they float to the top of the vat. This creates a froth (kind of like what forms when you bring homemade chicken soup to a boil, but even less tasty) which can be skimmed off. What’s left is a vat of clean, recycled pulp that is ready to become paper, or at least part of a sheet of paper. What makes floatation deinking work is hydrophobicity (and not "hydrophobia," as I had errantly stated earler -- that is rabies). Most adhesives and conventional printing inks repel water. But such is not the case with the inkjet inks used in digital printing, which are water soluble. That means they cannot be removed from the paper fiber through conventional flotation deinking, and will leave the paper into which they are made somewhat colored. (I achieved a similarly unpleasant result as a child, when I left my pet turtle in my shirt pocket, and mom washed it. But that is best left to another counseling session, I suppose.) There are at least two ways to address the turtle in the washer problem. One (DPDA’s approach) is to add some type of extra bleaching step to neutralize the colorant. DPDA used hydrosulfite bleach, and claimed success in deinking nearly all of the test colorants. INGEDE says the jury is still out on DPDA’s approach, and contends that deinking should be done through flotation, without the extra step. While the deinking associations are duking it out, manufacturers of inkjet products are exploring a variety of ways to address the colorant problem. HP is using a bonding agent that keeps the colorant out of the paper fibers. A Japanese company is trying encapsulation. And Xerox has developed a resin-based ink formulation. All of this to induce hydrophobia properties into in products that otherwise would take to water like a fish. How this all will shake out is anybody’s guess. But it will shake out. Because neither digital inkjet printing nor paper recycling are going away any time soon.