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 paper is a 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. Ilford Multigrade FB Classic is a 255 gsm double-weight baryta base with a neutral image colour, made in glossy (1K) and matt (5K) surfaces.

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. Ilford quotes the Multigrade RC core at 190 gsm (M-weight) or 250 gsm (K-weight) excluding the polythene, which adds roughly 70 gsm per square metre; the surfaces are coded glossy 1, satin 25, pearl 44. A finished FB print therefore consists only of paper, gelatin, metallic silver and inert baryta, while an RC print adds a polymer the older materials do not contain.

The same chemistry, different times

Because the bases differ only in whether the core wets, you can watch the consequence in identical chemistry. With Ilford Multigrade developer at 1+9 and 20C/68F, FB Classic develops in 1:30 to 3:00 (the image surfaces at about 20 seconds), while RC reaches full development in one minute, image visible after roughly 10 seconds. The fixer is the same too: a non-hardening Ilford Rapid Fixer or Hypam at 1+4, one minute for FB and 30 seconds for RC. A hardening fixer is explicitly not recommended, because it slows washing. The stop is Ilfostop 1+19 for 10 seconds on either base. The absorbent fibre core simply takes longer to take up and release chemistry, which is the whole story of the handling differences that follow.

Both papers carry seven full grades of contrast in half-grade steps under Multigrade filtration; filters 00 to 3.5 share a guide exposure, while filters 4 and 5 need roughly 1.5 to 2 times as long. Work under a safelight no lower than 580 nm (dark brown or red) and at least 1.2 m away.

The optimum permanence sequence, step by step

RC washing is trivial: two minutes in fresh running water, or 30 seconds with vigorous agitation. Ilford warns against leaving RC wet for more than 15 minutes, because prolonged immersion lets water penetrate the cut edges and brings on curl. The plastic that resists washing also resists over-washing.

Fibre is the opposite. The absorbent core soaks up fixer and its thiosulphate by-products, and clearing them is the difference between a print that lasts and one that yellows. Plain washing runs 30 to 45 minutes in running water above 5C. Ilford’s optimum permanence sequence for FB does the same job faster and more thoroughly, all baths held at 18 to 24C including the wash water:

• Fix in Rapid Fixer or Hypam 1+4 for one minute (do not extend fixing or exhaust the bath; both make washing harder)
• First wash, running water, 5 minutes
• Ilford Washaid (a hypo eliminator that strips thiosulphate by ion exchange) at 1+4, 10 minutes with intermittent agitation
• Final wash, running water, 5 minutes

If the print is selenium-toned for display, the final wash extends from 5 to 30 minutes. Do not add a hardener anywhere in the sequence.

How you know it actually washed

Washing rules are a means to an end, and the end is measurable. Residual thiosulphate left in the paper is what later oxidises and stains, so it can be quantified rather than assumed. The methylene blue method and the silver-sulphide densitometric method, both standardised in ISO 18917 (formerly ISO 417 / ANSI IT9.17), put a number on the residual fixer in a processed print. For a fibre print destined for an archive this is the link between the wash routine above and an actual permanence claim.

Drying then diverges as sharply as washing. Give FB a final rinse in Ilford Ilfotol wetting agent at 1+200, squeegee both sides, and dry flat under weight or in a press, because the wet core swells unevenly and dries with a pronounced curl. The same water uptake produces dry-down: a wet fibre print looks brighter than it will once dry, the highlights losing bite as the gelatin hardens. The effect typically runs 8 to 12 percent. Photographer Les McLean’s method is to reduce the final exposure by the measured percentage; on a 20-second base exposure, a 10 percent factor means printing at 18 seconds. RC, sealed against water, shows negligible dry-down and dries flat in 10 to 20 minutes at room temperature. It must never be glazed, ferrotyped or drum-dried, however: the polyethylene fuses to the glazing surface.

Toning and the polymer’s long memory

Ilford recommends toning display prints to protect them against oxidising gases in the air. Selenium toner works by converting part of the metallic silver image toward a more inert silver compound that resists those gases; on MG FB Classic it barely shifts the image colour but adds real protection, and the glossy 1K surface takes toner more readily than the matt 5K. Sulphide toning and silver-image stabilisers are alternatives.

The case for fibre as the archival medium rests on what it lacks: no polymer to fail. Resin-coated paper debuted commercially on Kodak Ektacolor in 1968, the first RC product; black-and-white makers including Agfa-Gevaert, Fuji, GAF, Ilford and 3M followed in the mid-1970s. Those early materials exposed the weakness of the route. The anatase form of titanium dioxide in the emulsion-side polyethylene photocatalyses under ultraviolet light to form singlet oxygen, which oxidises the polymer in chain-scission reactions, embrittling and cracking the base and accelerating silver mirroring in 1970s and 1980s prints. The American Institute for Conservation’s Photographic Materials Group, founded in 1979 with Henry Wilhelm among its founders, documents this history. Manufacturers since added antioxidants, peroxide scavengers and ultraviolet absorbers, but conservation literature is careful here: the formulations are proprietary and vary by product, so long-term longevity data remains limited. In cool, dry storage, around 18C or below at 30 to 50 percent relative humidity, both bases are expected to perform well; for prints on display, the conservation consensus still favours fibre, precisely because a fully washed and toned fibre print contains no plastic to degrade.