Surface texture of paper changing

[Davino]

The following is an AI analysis (Anthropic's Claude, Fable 5) of a longstanding issue I've sought for months to understand: what likely degraded a premium coated matte paper's surface feel across the full sheet—even in unprinted areas, front and back—compared to mill samples of the stock, which had a delicate, almost velvety drag when touched. Sheets returned from the printer felt hardened, more generic, likely more resilient, with no added coating applied, and its pleasing tactility, gone. The printer runs a Heidelberg Speedmaster XL 106-4 LED: 4-color offset printing press (750 x 1060 mm), and Speedmaster XL 106-8 LED: 8-color offset press. We're printing 4-color with one pms. I'm sharing this verbatim for expert scrutiny. These explanations, the only plausible ones I've found so far, are, however, a mechanistic inference not corroborated by print industry experts, which is why I'm posting them here.

The observed loss: mill samples of Arctic Volume White and Sappi Magno Volume (both coated matte stocks, 130 gsm) have a velvety, micro-rough tactile surface. Sheets returned from the printer's LED-UV press have lost this feel — including in unprinted margin areas, ruling out ink as the cause.

Proposed mechanism, three factors in combination:

1. Nip pressure (likely dominant). A matte coated stock's tactile character comes from a deliberately under-calendered coating surface — microscopic peaks and valleys in the mineral coating layer. Each pass through a printing unit presses the sheet between blanket and impression cylinder at significant pressure. This is functionally micro-calendering: it polishes the coating's peaks flat. A 5+5 job (CMYK + spot PMS, duplexed) means roughly twelve nips total. Calendering is literally how mills make paper smoother and glossier; the press repeats it. Critically, nip pressure applies to the entire sheet, printed or not — consistent with texture loss in virgin margins.
2. Fountain solution moisture cycling. Offset dampening wets the non-image plate areas every rotation; a micro-film of moisture transfers sheet-wide via the blanket. The coating absorbs some, swells slightly, and re-settles on drying — altering surface micro-structure. Under LED-UV, drying is near-instant rather than gradual, which is harsher on the surface structure.
3. LED-UV cure energy. Intense radiant energy flash-dries the surface and can slightly harden/embrittle the coating binder, deadening the surface's tactile "life."

Net effect: the sheet returns denser, smoother, harder, more moisture-resistant — and tactilely dead. The durability gain and the texture loss are the same event: the fragile micro-structure that produced the velvety drag is what got polished away.

Open questions I could not resolve: whether this degree of loss is typical for LED-UV sheet-fed work or worse than typical (i.e., whether this printer's nip pressures/dampening settings sit at the aggressive end of normal), and whether conventional offset — same nips, same dampening, no UV — would preserve meaningfully more surface character. Corrections welcome.