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Developer and fixer chemistry

ILFOSTOP PRO is specified on fixer sheets — Chemical Sundries does not document it

Shows that Ilford Rapid Fixer (July 2010; same structure in August 2002) and Hypam (August 2002) embed an ILFOSTOP / ILFOSTOP PRO stop-bath pair, publish different unreplenished capacities for the two products, and state that “ILFOSTOP PRO is recommended for all machine processing applications,” while the December 2017 Chemical Sundries sheet that is Ilford’s dedicated stop / wetting / washaid product document lists only ILFOSTOP, ILFOTOL and Washaid, publishes the ILFOSTOP capacities that match the fixer-sheet ILFOSTOP column, and says ILFOSTOP “is not recommended for machine processing applications” because of residual dye-stain risk — without naming or tabulating ILFOSTOP PRO; that the March 2002 2000RT machine-chemistry sheet tabulates only ILFOSTOP PRO (temperature band 20–40°C, RC capacity 90 sheets/litre); and that Multigrade FB Classic (October 2013) names only ILFOSTOP in its dish/tray processing summary.

Published by AnalogFixer ·

Ilford’s stop-bath story is often told as one product: ILFOSTOP at 1+19 for ten seconds. That is what the dedicated Chemical Sundries sheet documents. It is not the whole published set. The machine recommendation, and the second product that carries it, live inside fixer fact sheets that Sundries never names.

This is a document comparison of dated Ilford sheets. It is not a mixing, handling, reuse or disposal guide. Water-versus-stop framing across Kodak and Ilford sheets is a different kind of claim already treated in “Stop bath or running water” is not one manufacturer rule; the question here is which Ilford document carries ILFOSTOP PRO.

Fixer sheets publish the ILFOSTOP / ILFOSTOP PRO pair

Ilford Rapid Fixer, July 2010, under CHECKING AND MAINTAINING FIXER ACTIVITY / Stop Bath, recommends that films and papers be rinsed in an acid stop bath “such as ILFORD ILFOSTOP (with indicator dye) or ILFOSTOP PRO (without indicator dye).” The same block states that a stop bath in tank systems immediately stops development and reduces carry-over of excess developer into the fixer, which helps maintain fixer activity. It then says:

ILFOSTOP PRO is recommended for all machine processing applications.

The indicator-dye sentence that follows is scoped to ILFOSTOP: the dye turns from yellow to purple when the bath is exhausted, which “can be useful when dish/tray processing paper.”

The embedded ILFORD Stop Bath table then gives both products the same dilution (1+19), the same temperature range (18–24°C / 64–75°F), and the same time (10 seconds at 20°C / 68°F). The unreplenished capacities diverge:

ILFOSTOP ILFOSTOP PRO
Films / litre 15 × 135–36 22 × 135–36
RC paper / litre (20.3×25.4 cm / 8×10 in sheets) 60 90
FB paper / litre (same sheet size) 30 45

The August 2002 Rapid Fixer revision carries the same pair, the same machine recommendation for PRO, and the same capacity columns. Hypam, August 2002, reprints the same stop-bath prose and the same two-column table (with an extra specialist-materials film-area row that Rapid’s July 2010 table does not carry). On these fixer sheets, ILFOSTOP PRO is not a rumour product. It is tabulated beside ILFOSTOP and named as the machine path.

Matrix showing ILFOSTOP PRO documented on fixer sheets but absent from Chemical Sundries sheet.

Chemical Sundries documents ILFOSTOP alone — and bans it for machines

HARMAN technology’s Sundry chemicals for processing black and white films and papers sheet, updated December 2017, is the product document whose masthead lists three chemicals: ILFOSTOP, ILFOTOL and Washaid. Its opening sentence says the sundries range includes “a stop bath, wetting agent and a hypo-clearing agent.” The stop bath treated in the body is ILFOSTOP only.

That ILFOSTOP block matches the fixer-sheet ILFOSTOP column on the working figures that matter here: dilution 1+19; temperature 18–24°C (64–75°F); time for film and paper at 20°C of 10 seconds; unreplenished capacities 15×135–36 films, 60 RC sheets, and 30 FB sheets per litre. A full-document search of the Sundries PDF examined here finds no occurrence of the string ILFOSTOP PRO.

Sundries also publishes the machine claim that the fixer sheets assign to the other product. After recommending ILFOSTOP for dish/tray paper or deep-tank film work, it states that ILFOSTOP “is not recommended for machine processing applications as the short fix and wash times often used may leave a residual dye stain on films and prints,” and that longer wash times in dish/tray and tank processing minimise that risk.

So the dedicated stop-bath sheet does two things at once. It is the place a reader would expect the full stop-bath product line. It documents only the indicator product. And it forbids that indicator product for machine work for a dye-stain reason — without pointing to ILFOSTOP PRO, without reprinting the fixer-sheet PRO capacities, and without restating the fixer sheets’ “PRO is recommended for all machine processing applications” sentence.

2000RT tabulates only PRO — with a wider temperature band

Ilford 2000RT, March 2002, is a machine RC paper developer/fixer sheet. Its stop-bath block does not offer the ILFOSTOP / PRO pair. When a stop bath can be used, it says ILFOSTOP PRO is recommended for all machine processing applications, and its ILFORD Stop Bath table has a single column: ILFOSTOP PRO. That sheet also publishes RC silver permanence targets beside bath-capacity figures; see What fixer exhaustion actually means for how those silver thresholds differ from throughput labels on the same manufacturer sheets.

That PRO column agrees with the fixer-sheet PRO capacities on RC paper (90 sheets of 20.3×25.4 cm per litre, unreplenished) and with the 1+19 / 10-second clock at 20°C. It does not agree on temperature range. Rapid Fixer and Hypam embed 18–24°C for both ILFOSTOP and PRO. 2000RT gives PRO 20–40°C (68–104°F) and adds a replenishment-rate band (100–200 ml/m²) that the Rapid/Hypam stop tables do not publish.

So even the PRO role is not one number set. The machine-chemistry sheet that names only PRO widens the temperature band and adds replenishment; the general fixer sheets that embed PRO beside ILFOSTOP keep the narrower 18–24°C band.

Multigrade’s dish path names only ILFOSTOP

Multigrade FB Classic, October 2013, is a fibre-base paper sheet written for dish/tray work. Its processing summary lists stop bath as ILFOSTOP at 1+19, 18–24°C / 64–75°F, for 0:10. It does not name ILFOSTOP PRO. That is consistent with Sundries’ dish/tray framing for ILFOSTOP. It is not a second copy of the fixer-sheet machine path, and it does not fill the Sundries silence about PRO.

Rapid Fixer, July 2010 / Hypam, August 2002 Chemical Sundries, Dec 2017 2000RT, March 2002 Multigrade FB Classic, Oct 2013
Document class Fixer fact sheet with embedded stop table Dedicated sundries product sheet Machine RC developer/fixer sheet Fibre-base paper processing sheet
ILFOSTOP named Yes (with indicator) Yes (only stop product treated) No Yes
ILFOSTOP PRO named Yes (without indicator); machine recommendation No (ILFOSTOP PRO absent) Yes; only stop product tabulated No
Machine framing PRO recommended for all machine applications ILFOSTOP not recommended for machine applications (dye-stain risk) PRO recommended when a stop bath can be used Not a machine sheet; dish/tray summary only
PRO temperature on that sheet 18–24°C (shared with ILFOSTOP) Not published 20–40°C Not published

What these sheets do not settle

None of these documents is used here to rank ILFOSTOP against ILFOSTOP PRO for stop efficiency, to prove that dye stain occurs at a stated wash time, or to treat the 2000RT 20–40°C band as superseding the Rapid/Hypam 18–24°C PRO row. No dedicated ILFOSTOP PRO stand-alone fact sheet was examined for this article; PRO figures are taken from the fixer and 2000RT embeds. Live ilfordphoto.com amfile endpoints failed during retrieval checks for this article, so citations use Wayback and public mirrors whose bytes match the local evidence mirrors. Whether a later inaccessible sundries revision restores PRO is outside what these files examined here prove.

The usable statement is narrower. In the sources examined here, “Ilford’s stop bath” is ILFOSTOP where Chemical Sundries and Multigrade say so; ILFOSTOP or ILFOSTOP PRO where Rapid Fixer and Hypam embed both; and ILFOSTOP PRO alone where 2000RT tabulates the machine path. Collapsing that into one house stop product erases the document split that puts the machine recommendation on fixer sheets the sundries sheet does not cross-reference.

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