ILFORD Type RX Recording Film

The following information originated from Sue, of Harman Technology, in response to a query by David Mittelstadt (member of the APUG forum website) who wanted to know the original use of a roll of bulk film (400 feet left out of an original 1,000ft - 300m - length, on a 2" core) that he had purchased. No ASA speed or processing data was marked on David's film packaging.
Sue's information is presented here for future reference.
Although Sue's information correctly refers to Type RX film (expiry date 1964) as owned by David Mittelstadt, Michael Talbert found reference in a 1967 Ilford catalogue, to an Improved Type RX film.

RX recording film
The only reference I can find to us (i.e. Ilford, Ltd.) manufacturing an RX film - is a product called RX recording film. This was a medium speed panchromatic film - thinly coated and highly pre-hardened to enable it to be processed rapidly at high temperatures.
RX recording film had high speed at short exposure times, so it was especially suitable for recording displays on cathode-ray oscilloscopes.
RX was suitable for use with both the short persistence phosphors and the long afterglow types generally used for plan position indicator (PPI) recording.

Ferranti phosphors A (equivalent to the American P24), C, G, H and J all give good exposure response, particularly the A and C phosphors for short persistence.
H and J phosphors have long afterglow characteristics and are very suitable for radar echo response with RX.
Blue emitting phosphors P and Q (equivalent respectively to American P11 and P16) are also suitable.

RX was originally designed in conjunction with the Kelvin Hughes RP3 Rapid Processing photographic projector for both PPI and data processing radar displays.

RX may be processed to a negative record but is particularly suitable for processing to a silver halide reversal positive. It is used in conjunction with the RPI equipment to provide rapid access of subjects such as racecourse finishes.

RX is coated on a 0.13mm (5/1000 inch) safety base, permanently grey-dyed for anti-halation purposes.

The high contrast resolving power of RX when processed to a negative by the methods given below (under Processing) is as follows:-
Resolving power (lines per mm)
Ilford filter 304 (tri-colour blue) - 135
Ilford filter 110 (minus blue) - 155

Safelights - It is sensitive to light of all colours and should be handled in total darkness. A 908 (very dark green) safelight can be used to help during development stages, but needs to be used with a lot of care.

Exposure - Using high quality cathode ray tubes with a final anode potential of 15kV and a beam current of 0.5 to 1.0µA, RX film can record, at a lens aperture of f1.4, a writing speed on the film of 10,000 cm per second.
Since RX is intended for highly specialised use, accurate speed ratings cannot be given.
In practice, however, the use of meter settings at some figure within the range of 50-100 ASA (18-21 Din) will normally result in a satisfactory level of exposure.

Processing - The processing of RX is achieved most rapidly in the Kelvin Hughes and other types of rapid access equipment.
A halide reversal positive is produced by first developing to a negative and then bleaching out the resulting negative silver image. The remaining halide image is of low contrast when viewed by diffuse illumination, but with the specular illumination conditions associated with projection viewing, the contrast is much higher.
Typical processing times in the Kelvin Hughes RP3 equipment are from 3 to 25 seconds.
The following chemicals need to be used in Kelvin Hughes equipment:
ID-57 Developer,
IB-11 bleach or Bleach solution 285
IF-18 or IF-24 fixer
IS-2 or IS-3 Wash crystals.
RX may also be processed less rapidly by using ID-33 Developer and Hypam fixer. Development time at 20°C (68°F) is then 5 minutes using a 1+4 dilution.
Alternatively, at 35°C (95°F), the ID-33 development time is 45secs using a 1+5 dilution.

Michael Talbert adds:
Ilford “Phentrace PQ” developer was recommended for recording films. This developer could be used at the very high temperatures for fast processing. It was the developer for automatic processing machines, dilution, 1 + 2 to 1 + 5.
ID-33 was the developer recommended before Phentrace.
ID-33 is still mentioned in the Ilford 1967 catalogue as well as in the 1956 catalogue.
In 1967, ID-33 was discontinued and Ilford suggested using ID-19 as a replacement. ID-19 was a MQ developer used for aerial films or whenever high contrast was wanted.

This page last updated: 6th May 2012