The choice between fibre-based (FB) and resin-coated (RC) paper is not a matter of taste alone. The two share the same silver-gelatin emulsion chemistry but rest on fundamentally different supports, and that single structural difference governs how a print is washed, dried, toned and how long it survives. Understanding the construction explains the handling rules rather than requiring them to be memorised.

Two ways to support an emulsion

A fibre-based paper, as Ilford describes it, is a high-quality paper base with a layer of barium sulphate (baryta) calendered onto one surface to give a smooth, reflective white ground before the emulsion is coated. The paper itself remains exposed and absorbent. The baryta layer is chemically inert; it brightens the image through its reflectivity and prevents impurities in the paper from migrating into the emulsion.

Resin-coated paper inverts that logic. The paper core is sealed between two layers of polyethylene, the emulsion-side layer pigmented with titanium dioxide for opacity and whiteness. The paper fibres are never wetted during processing because the plastic skins are impermeable. A finished FB print therefore consists only of paper, gelatin, metallic silver and inert baryta, while an RC print adds a polymer that the older materials do not contain.

Washing and drying consequences

Because RC paper does not absorb chemistry into its core, only the thin emulsion needs clearing. Ilford notes that a brief wash of around a minute or two in fresh water suffices, and the print dries flat and quickly at room temperature. Fibre base behaves oppositely: the absorbent core takes up fixer and its by-products, demanding extended washing, typically with a hypo clearing or wash-aid step to displace residual thiosulphate before a final rinse. Ilford’s archival, or optimum permanence, sequence is built around minimising the residual chemistry that shortens a fibre print’s life.

Drying is equally divergent. Wet fibre paper swells unevenly and dries with a pronounced curl, usually requiring flattening under weight or in a press. This water uptake also produces dry-down: a damp fibre print appears lighter and softer than the same print once dry, so prints are commonly exposed slightly darker to compensate. RC paper, sealed against water, shows negligible dry-down.

Toning response and archival life

Both supports take selenium and other toners, but the fibre base, with its exposed paper and baryta, often yields deeper and more visible shifts. More significantly, longevity differs by construction. Ilford recommends fibre base as the medium of choice where long-term archival stability is the priority, precisely because a fully washed and toned fibre print contains no plastic to degrade.

Early RC papers, introduced commercially in the late 1960s, exposed the weakness of the polymer route. Conservation literature from the American Institute for Conservation’s Photographic Materials Group records that the titanium dioxide pigment generated free radicals under light, driving chain scission and embrittlement of the polyethylene and accelerating silver mirroring. Manufacturers responded from around 1979 onward with stabiliser systems and hindered-amine additives that greatly delayed cracking. Modern RC papers are far more durable than their predecessors, yet for prints intended to last generations, the simpler fibre construction remains the conservative choice.