Extracted from the 1955 BJPA, pages 260-262)

PAKOLOR FILM, PAPER AND CHEMICALS
(Associated British-Pathe Ltd., Pathe House, 133-135 Oxford Street, London, W.l)
When Pakolor negative colour film was first introduced a little over two years ago only the film itself was supplied, and processing, and printing was undertaken by the laboratory operated by the distributors.

Now the process as a whole is available for operation by the photographer at all stages. As such it will now be of interest to professional photographers and to amateurs who wish to make their own colour prints by a negative-positive process.

The processing outfit (which is made by Johnsons of Hendon) consists of three components, the developer, the stop bath, and the bleach-fix. All are supplied as dry chemicals and the developer makes 4 litres, the stop bath 1 litre of stock solution, and the bleach-fix 1 litre of working solution. The developer is made up as three stock solutions, which is always a good system for colour developers, and in this state will keep for several months in well-stoppered bottles.

The processing chemicals are used for both film and paper processing, the stop bath and bleach-fix being used interchangeably for both materials. The developer stock solutions are used in different proportions according to whether the working bath is to be used for film or paper. A hardener-stabiliser bath is also used for both the film and the paper and this is not supplied in the kit. However, this is a simple solution consisting of 20c.c. of 40 per cent formaldehyde and 2.5 gm. of anhydrous sodium carbonate per litre.

The speed of Pakolor negative film is Weston 8 (ASA 10 or BS 21 degs.) and tests confirm that this rating can be used with confidence for average subjects. As the instruction leaflet suggests, subjects with a preponderance of shadow area can be given about half a stop more exposure than the rating indicates and flat subjects can be given half a stop less.

The film is developed in entirely orthodox fashion using either the conventional spiral-groove tanks for roll-film or deep tanks for sheet film. The film-processing schedule is as alongside (left):-

Thus far, it will be seen the process corresponds fairly closely with the handling of black-and-white material and indeed tests show that provided that the temperature of the developer is held at 65°F. within the usual ½°F tolerance prescribed for colour film, colour negatives of good gradation and excellent general quality can be obtained with no more difficulty than is normally experienced using black-and-white film.

Printing, however, as one might expect, is somewhat more complex. Exposure of the print in three steps by the tricolor filter technique simplifies the achievement of correct colour balance, and the use of the combined bleach-fix bath reduces the number of processing solutions needed.

The three exposures are made through a special set of tricolour filters which can be obtained either as separate gelatin sheets or ready mounted in a filter-disc assembly which is held on the enlarger lens mount by three set-screws.

For handling the paper, which is, in effect, panchromatic in sensitivity, a moderately bright olive-green safelight is supplied.

The fact that the three emulsion layers of the paper are separately exposed means that some precautions must be taken to avoid differences of size or position of the three images in printing. It is recommended, for example, that glass carriers should be used in the enlarger since exposures are rather longer than are usual with black-and-white materials and there would be a risk of heat causing the negative to distort and change its position between the exposures. Similarly it is advisable to be sure that the enlarger lens mount, on to which the filter disc is fitted, is reasonably firm.

A voltage-control unit is naturally a help in maintaining consistency of colour balance with this process as with any other.

The method adopted to expose a test which will provide some indication of the exposures needed through the three filters for a particular negative is a simple modification of the system generally used in black-and-white practice. A small sheet of paper (say about 3x2 in.) is used and is given a series of increasing exposure times in one direction through the red filter. The filter is then changed to green and a series of exposures again given but in this case the mask is moved at right-angles to the direction used for the red filter exposures. A final over-all exposure is given through the blue filter the amount being some arbitrary time for the first test.

After processing the test will show an equal amount of yellow throughout and rectangles of increasing cyan density across the picture area and increasing magenta in a vertical direction. At least one of these rectangles should show something approaching correct balance and will thus give some indication on which a further test can be made.

The processsing schedule for paper is as alongside (left):-

When carefully handled the paper gave prints of good saturation and with clean whites. In addition to paper with a glossy surface, matt-surface paper is also available and positive film for the production of transparencies from the colour negatives can also be obtained. The latter material is processed in the same solutions as are used for paper but with a colour-development time of 10 minutes instead of the 6 minutes used for paper. The transparency film should be a useful material for photographers who wish to make large quantities of colour transparencies for display purposes.

All of these sensitive materials are products of good quality, and when properly used the Pakolor process will give results which compare extremely favourably with any other system of the negative-positive type.

Pakolor roll-film in 20 and 62 sizes is priced at 11s. 2d. plus 3s. l0d. purchase tax per 8-exposure roll, 35-mm. film is 13s. 5d. plus 4s. 7d. purchase tax for a 20-exposure cassette, 20-exposure refills are 11s. 0d. plus 3s. 10d. purchase tax and 25-ft. lengths cost £2 4s. 0d. plus 14s. 8d. purchase tax. The prices of sheet film range from £1 2s. 6d. plus 7s. 9d. purchase tax for quarter-plate size to £6 0s. 0d. plus £2 1s. 0d. purchase tax for 10 x 8 in., per box of 10 sheets in each case.

With the exception of the 2½ x 3½in. size, Pakolor paper is available in either 10-sheet or 25-sheet packets; the small size is available only in 25-sheet packets which cost 9s. 9d. plus 3s. 2d. purchase tax. The price of paper ranges from 6s. 9d. plus 2s. 3d. purchase tax for 10 sheets of quarter-plate size to £1 12s. 6d. plus 10s. 10d. purchase tax for 10 sheets of 10x8 in. Other sizes between these limits are in proportion.
The set of filters in card mounts costs 14s. 7d. plus 4s. 11d. purchase tax and the filter turret costs either £5 1s. 3d. plus £1 13s. 9d. purchase tax or £4 14s. 6d. plus £1. 11s. 6d. purchase tax depending whether it is required to fit on lenses larger or smaller than 32-mm. diameter.

The processing kit to make the quantities specified earlier costs 35s. 3d. and a 5x7in safelight screen costs 9s. 6d. The 10x8in safelight screen costs 12s. 3d. A complete Pakolor processing and printing outfit No.1 costs £3 2s. 6d. plus 5s. 3d. purchase tax.