Inks That Behave Badly

What the Ink Is Actually Doing Wrong

Skinning is the one that sneaks up on you. You open a tin or jar that's been sitting for a while — weeks, sometimes less if the lid wasn't seated properly — and the surface has formed a thin, rubbery membrane. The ink beneath can be perfectly usable, but the skin itself is a contaminant: pull it out cleanly, scrape it off the rim, don't let fragments mix back in. If you print with skin fragments in the ink, they show up as raised flecks in the film, which read as texture you didn't choose. Prevention is straightforward: press a piece of cling film or waxed paper directly against the ink surface before closing the lid. The ink can't skin if it can't access air.

Chalking is subtler and more demoralising because it doesn't announce itself immediately. The printed ink appears to dry, but when you run a finger across it, pigment comes away as powder. What's happened is that the vehicle — the oil or binder carrying the pigment — has been absorbed too quickly into the substrate, leaving the pigment particles sitting on the surface without enough binder to hold them together. Absorbent papers, particularly uncoated stocks with high porosity, are the usual culprits. A sizing issue in the paper, or paper that's genuinely too lightweight for the ink being used, will do it. You can sometimes rescue the print by applying a very light fixative, but you're working after the fact. The smarter adjustment is to either reduce ink absorbency by choosing a more sized or coated stock, or shift to an ink with a stronger binder-to-pigment ratio. Some printers add a small amount of reducing medium — not a drying medium, which is different — to slow vehicle absorption, but this changes tack and body, so test before committing.

Set-off is the sheet stacked on top of a freshly printed sheet picking up a ghost of the image. It happens when you print too wet and interleave or stack without adequate drying time. The obvious fix is patience, but that's not always practical. Slip-sheeting — placing a clean sheet between each printed sheet — is the classical answer. Newsprint, tissue: anything clean that won't itself contaminate the print. Anti-set-off powder, finely sprayed over a print immediately after it's pulled, creates a microscopic barrier between sheets; it's standard in commercial lithography and perfectly viable at bench scale if you can source it in small quantities. Be aware that any powder risks interfering with subsequent overprinting or other handling, so it's a final-stage intervention, not a mid-process one.

Failures That Look Like Each Other

A few failure modes are commonly misread. Ink that appears chalked but resists rubbing is more likely to be over-reduced — too much transparent base or extender added, dropping the pigment load below what produces a robust film. The test: if it rubs away as powder, chalking; if it smears, something else.

Mottling — a blotchy, uneven ink distribution — gets blamed on the ink when it's often the paper. Inconsistent surface sizing across the sheet creates inconsistent absorbency, and the ink lands differently in different areas. The ink isn't misbehaving; the paper is. Switching stock is faster than reformulating the ink.

Tack failure — ink that transfers unevenly to the substrate, especially on a second pass — usually points to ink that's too stiff for the conditions, or a substrate with too much release in its coating. Neither diagnosis is complicated once you know what you're looking at.

Most of these problems are visible before the print is dry, which is why slowing down to look at each pull before the next one is less about perfectionism and more about catching something recoverable before it's an edition.