Spiral Loading Developing Tank History

In the earliest days of plate and cut film developing, when emulsion speeds were slow and spectral sensitivity was mostly towards blue light, it was convenient to develop images individually, laid flat in developing trays, checking their development by visual inspection using a relatively bright red darkroom safe light. By the early 20th century, the invention of roll film had complicated things somewhat, but a simple method of development was soon established.

By taking advantage of bright red safelighting suited to orthochromatic films, roll films could be manually 'see-sawed' up and down through developer in a shallow dish (and similarly through stop bath & fixer). This technique was still advised in the 1950s for those wishing to 'have a go' at processing (orthochromatic) films at home, without the added expense of buying a developing tank.

Photax sold (mid-1950s) a simple Developing Trough (right), consisting of a deep, curved base developing tray, with a roller.

By feeding the film under the roller, a user could have reasonable assurance that his film would stay correctly immersed within the developer throughout the developing process, even with minimal safe-lighting. Thus, with care, the Photax developing trough made possible the see-saw dish developing of even panchromatic film.

The pictures alongside are courtesy of Brian Rees. They show another 'assisted' method by which roll film could be 'see saw' dish developed, possibly in total darkness as required by Panchromatic film.

The device is the Granitine Developing Tray with Trident Roll Film Weight. It was made in white porcelain by Taylor, Tunnicliffe & Co of Stoke-On-Trent, England at the beginning of the 20th Century.
The following is printed on the Trident:
The Trident shape is sufficiently heavy that it could be relied upon to have stayed in position while the film was being 'see sawed' back and forth through developer held within the porcelain dish. No doubt a small amount of practice would have been required to perfect the process in total darkness, but it would certainly have been possible.
Approx. Dish Dimensions are 140mm x 115mm x 38mm.

The film would have been looped under the central 'finger' of the Trident, with its sensitive emulsion to the outside of the finger's curve, so that the emulsion would not have been damaged by abrasion while the film was pulled back & forth in reasonably firm contact with the central finger.

Problems were magnified in the 1930s, when the Leica & Contax cameras (and increasingly many others) introduced the concept of using lengths of 35mm motion picture film stock for 'still' photography. The film lengths were too long for see-saw dish developing (a standard 36exp 35mm film is over 5ft long i.e. 1.5m). Fine grain developers, as required by miniature negatives, also introduced softer working developers with longer film processing times, making manual see-saw dish development tedious. So, together with increased film speeds and panchromatic emulsions, preventing the use of red safelights, a new approach was required to (home) film development.

Commercial laboratories relied upon deep, open-top, tanks in darkrooms, with films suspended vertically, dozens at a time, an arrangement uneconomic for occasional film developing by an amateur working at home. Deep tank commercial processing was not without its problems as film could suffer from uneven development if adjacent films stuck to one another as they were lowered (maybe 8 at a time on a single 'hanger' rod) into the developer. It was necessary for the operator to make sure this hadn't happened, by subsequently checking, using his/her hand, that all the films were hanging separately.

Despite the relative impracticality of see-sawing processing 35mm film, at least one manufacturer tried to persist with equipment designed for this technique. The economical 'DIMPLE' developing dish was sold for the purpose. A full pdf of the instruction sheet can be downloaded here. Its method of use is illustrated below.

Each 'Dimple' dish measures some 95mm wide (top length) by 50mm wide by 35mm deep (internally). The dish is made of white, glazed, ceramic. The 'dimples' which give the device its name, serve two purposes. Their main use is to form protrusions inside the dish from each side, and so provide a reduced width channel which traps the film while it is see-sawed back and forth.

Their second use, as shown in the picture (right, above), is to enable the dish to be anchored down to a wooden board by means of 'S' bracket 'clips' (though these may not have been supplied with the dish(es) and may have been something a user had to improvise).

This information is courtesy of Brian Rees.

Further to the problem of the amateur enthusiast seeking to process his 35mm films at home, the 'focal' Photo Guide No.46 (1956) by Percy W Harris contains a useful description of how ideas progressed. He writes:

"First of all the user (of 35mm) could use a horizontal glass drum round which the film was wound (emulsion side out), the underside of the drum rotating in a dish of developer. That was not a particularly efficient solution to the problem, so the developing tank was introduced (probably from the early 1930s - see the EARLY PATENT history, below).

'Apron' Spiral Loading Tanks
The first tank had a circular moulded plastic body with a light-tight lid. Inside was a plastic bobbin (reel) with plain end faces, between which could be wound a length of celluloid (called an 'apron'), the same width as the film. This apron had little projections on its edges so that when the photographic film was wound within it, the film was touched only by the projections.

As they touched only the perforated part of the film and not the picture itself, the developer had access to all the picture area. Once the loaded reel had been placed inside the light-tight tank in the darkroom, the whole thing could be brought out into normal lighting. The necessary chemicals were then poured in and out without exposing the film to light. This soon became the standard way to develop 35mm films."

Alongside is illustrated a 'Correx', one of the earliest tanks of this type. The illustration is taken from 'Amateur Photography', edited by Anthony Johnstone, 7th edition (revised) 1951.

Centre vs Peripheral Loading Spiral
A little later, another type of light-tight tank appeared. In this design, instead of the reel having plain ends, separated by the width of the apron, the reel ends were made with spiral grooves and no apron was required. To load the reel, the film is inserted into the beginning of the groove (or sometimes clipped to the central shaft of the spiral) and pushed in from the outermost groove of the spiral towards the centre, until the end of the film is reached (or wound into the spiral, starting from the groove centre - this design requires the film to be momentarily bent lengthwise as it is loaded, so as to reduce the film width and allow it to 'spring' into the spiral groove).

Which is better?
Loading the apron type of tank is quite easy, but the disadvantage is that it is rather a messy business taking the film out of a wet apron. The wet apron takes a long time to dry because you get water in the dimples. Also, at the loading stage you have to take special precautions to prevent the apron collecting dirt from the floor. On the other hand, spiral groove tanks can sometimes give trouble in loading by the 'push-in' method, when the film may stick before it is fully inserted.

Mr Harris then goes on to describe the 'recently introduced' self-loading spiral groove tanks with the the facility to contra-rotate the ends of the spiral reel through part of a turn. He mentions that some self-loading spiral reels have a ratchet arrangement to assist the film along the groove (the Paterson patent) while others have no ratchet but are loaded in the same way by using alternate thumbs to hold the edge of the film as the reel ends are rotated one way and then the other.

Daylight Loading Developing Tanks
Finally, he mentions how some people found using a darkroom, even just to load their developing tank, was inconvenient and a demand arose for tanks which could be loaded completely in the daylight. A range of such tanks were made in Austria and imported by The Norse Trading Co. (London) Ltd. The Superkino took 35mm film, the Simplex took 120/620 roll film and the Super-Junoplex took 127 roll film. They were advertised on p653 of the BJPA for 1937. The exposed film was placed in the tank's side chamber and means was provided by which the film could then be wound onto a grooved spiral within the main tank body, while the tank and photographer remained in daylight. For more information on the Simplex tank, click here.

Another tank by the same Austrian manufacturer, suited to 127, 120/620, 116/616 roll films was the Superplex. Pictures and information on this tank can be seen here.

As shown in the 1952 Photax advert, below, there was a 35mm Daylight Loading tank available, which Photax advertised using the name SuperFlex. But there is some mystery about this name, since even in Photax's own advert, the name on the lid of the 'SuperFlex' can be seen to read 'Super-Plex'. The daylight loading SuperFlex (or, more correctly, Super-Plex) seems the equivalent of the earlier Superkino (see Norse Trading advert, left). The difference is that the post-War Super-Plex incorporated a 'cutter' to cut off exposed lengths of 35mm film, leaving the unexposed portion still in the cassette for later use. For detailed views of the Super-Plex tank, sent to me by Neil Dunbar, click here.

Daylight loading designs were comparatively expensive. By way of example, the roll film Simplex was priced at £1.17s.6d (£1.88) see advert alongside, while the more complex Superplex was priced at £2.5s (£2.25p). Comparing these 1937 prices to 2008 purchasing power, the Simplex in 2008 would need to cost £350 to 'feel' as expensive. Even on a simple Retail Price Index (inflationary) comparison, its cost would inflate to £90. The Superplex price would inflate to £108. In comparison with a similar darkroom loading tank of the time, the Simplex Daylight tank cost roughly twice as much.

It seems the pre-WW2 Austrian manufacturer of the above tank range still manufactured and exported to the UK after the War, but with Photax (London) Ltd. as the distributors. The illustration, right, is from a November 1952 issue of Amateur Photographer magazine.

The darkroom loading tanks incorporated automatic up-and-down movement of the spiral during development by the simple expedient of shaped projections on the underside of the centre column of the spiral acting as cams to lift and drop the spiral as it rotated during agitation. This idea, or similar, became near universally applied around this time. However, it wasn't a new idea; the Kinofilmtank (peripheral loading spiral design for 35mm film) had this arrangement when tested by 'The Miniature Camera Magazine' in October 1937.

The feature enabling the cutting off of exposed lengths of film for development, as in the Super-Plex, continued in the Essex daylight loading 35mm tank (see below) distributed by Johnsons of Hendon.

The 'Essex' 35mm daylight loading tank was based upon the pre-War German Agfa Rondinax 35U design. The improved UK version was priced at £4.18s.6d (£4.93).

The Essex and Kent-20 Dayight Loading developing tanks were sold in the early 1950s by Johnsons of Hendon and Neville Brown & Co Ltd (Nebro). They were based upon the pre-WW2 Agfa Rondinax 35 U and 60 tanks and may have been manufactured by Agfa for UK distribution by Johnsons and Nebro.

Below are some images of contemporary Agfa Rondinax 35U and Rondinax 60 tanks (the latter courtesy of Brian Rees who also loaned me the Rondinax 35U to photograph). These pictures can be understood by being viewed in conjunction with the Agfa instruction booklets (Rondinax 60 here and Rondinax 35U here).

My thanks to Richard Urmonas for making these instruction booklets available. His website can be viewed at: http://www.urmonas.net/index.html

Brian Rees has donated (July 2014) what seems to be a version of the original Rondinax 35 U instructions, unfortunately missing its front and back covers. Click here to download it as a pdf. 

The Kent-20 is the UK version of the German designed Rondinax 60 daylight tank and does for 120 film what the 'Essex' does for 35mm. It cost £4.5s (£4.25).

Rondinax 35 U Daylight Loading 35mm Film Tank



Rondinax 60 Daylight Loading 120 Roll Film Tank

Rondix 35 Daylight Loading 35mm Film Tank

Description and Photographs taken from Modern Camera Magazine (MCM) for Nov. 1957

The new Agfa 'Rondix' daylight loading developing tank in parts (above) and ready for use (right).

Rondix 35

It is not often that one comes across something entirely new in the way of developing tanks, for most of them follow the well tried spiral groove method. The new Agfa Rondix 35, which we saw first at Photo Kina 1956 is now on sale in this country and is a most interesting device. At first glance, and from the outside, it looks rather like the well-known Rondinax 35, but it is appreciably smaller and works on quite a different principle. Let us explain first of all what it aims to do and how it does it.

The Rondix is a completely daylight developing tank designed for the ordinary velvet light-trapped 35mm film cassettes, both loading and processing taking place in full light, no darkroom being required. The tank, which takes only 6½oz. of solution, has a receptacle at one end which takes the cassette.

As soon as the film in the cassette has been fully exposed in the camera it is wound back into the cassette, but with a little of the tongue still projecting from the light-trap. This projecting tongue is pulled out so that not more than 3cm of the full width of the film projects from the cassette and the tongue itself is cut off square. When we remove the lid on the Rondix, unscrew the handle from the side and pull out the spindle, we find we can remove a small central bobbin l¼ins in diameter, which has a spring clip to which the perforations of the end of the film can be attached.

The cassette, with its projecting film attached to the bobbin, is now dropped into the tank, the spindle reinserted and the light tight lid replaced. The developer is now poured into the tank and the handle slowly turned at the rate of one-half revolution per second until resistance is felt, which means we have come to the end of the film. Immediately the crank is turned in the reverse direction but now at a higher speed, i.e. 1 to l½ revolutions per second, and this speed must be maintained throughout the rest of the processing. Whenever a check is felt the turning is once more reversed, this turning backwards and forwards being continued, as we have indicated, until the developing time is up, after which the developer is poured out, rinse water poured in, followed by fixing. At the end of the fixing period the film should be completely removed from the tank and washed separately.

The novelty about this tank is the actual method of passing the film through the solution. Unlike other tanks, there is no plastic spiral and all that happens when you start turning is that the film is wound on to the small central bobbin, most of which is below the level of the developer. The film is completely wound on to this central bobbin with all the turns touching just as they are in the dry cassette, the film so to speak taking developer with it into its coil. However, as soon as the whole film is wound on we reverse the turning, and this unwinds the film loosely inside until we come to the attached end, whereupon it is once more wound on to the bobbin, but this time with the emulsion side inwards. Then, again when we reach the end, we loosen it once more, wind on with the emulsion outwards and so on backwards and forwards, until the end of the time. In this way a constant supply of fresh developer is provided for the whole surface and careful examination of our test film showed that development was completely uniform, with no sign of surface injury or scratching. The only precautions to be taken are to see that the handle is kept moving all the time.

The Rondix 35 tank is designed, as we have said, for the velvet light-trap cassettes in which manufacturers sell their films. It is necessary to point out that these cassettes cannot be used again because the developer tends to splash into the light-trap of the cassette, and so it must be thrown away after use. Nor will the tank take the metal self-opening cassettes such as those supplied for the Leica and Contax and other Zeiss Ikon cameras, or the Shirley-Wellard.

The simplicity of the design of this tank enables it to be sold at £2.12s.6d (£2.63p) which is less than half the cost of the Rondinax 35. This latter, however, has advantages over the Rondix in that it will take any of the cassettes, velvet light-trap or self-opening and, if desired, the ordinary velvet light-trap cassettes can be used again, although we do not recommend such a procedure.

While looking at the more unusual developing tank designs, the one shown left is another from Austria and is a novel way of incorporating multiple spirals into a single enclosure enabling simultaneous development of films. Instead of a tall tank, taking multiple spirals one above the other, the Tribox is a horizontal design with three spirals linked by a central geared spindle, such that all 3 spirals rotate together for agitation. The disadvantage of this design is that one cannot choose to develop just one film and use the developer quantity to cover just one spiral. The developer volume is fixed regardless of how many spirals are in use.

It emptied through a novel valve in the bottom, controlled by a spring-loaded shaft. A single nut served to lock both the valve and the tank lid.

The 'Tribox' advert (far left) claims that up to 6 35mm films can be processed 'back to back', 2 on each of the 3 spirals. Whether this means 2 off 20exposure 35mm films inserted one after the other, end to end, or really does mean 2 off 36exposure films, 'back to back', isn't clear. If the latter, this is an unusual claim which other manufacturers were reluctant to advise. As can be seen, the price, in September 1952, was £3.17s.6d (£3.88). An electric powered agitator cost £18.

To see and read about an Envoy (Photo Developments Ltd) tank designed for developing glass plates, click here.

ILFORD Developing Tanks

One of the earliest spiral loading developing tanks on the British market must have been this one, as sold by Ilford before WW2, possibly 1938. It was supplied in a heavy weight cardboard box, some 150mm x 150mm x 115mm deep.

The box lid shows the paddle steamer trade mark (below) which is the 1930-1945 version of the four shown near the top of the Ilford chronology web page.

The Ilford Developing Tank box lid, showing the four different film sizes it accepts, viz:
(116 & 616; 117; 120 & 620; 127)
but since No.17 and 20 roll films are both 6cm wide, the tank only requires three reel to reel width separation 'notches' (6cm for the above, 4cm for 127 and 6.5cm for 116 & 616).
Notice, there is no facility for 35mm.

Paul Godfrey suggests that the tank was probably made by British Xylonite Plastics Ltd, known as B.X. Plastics Ltd in 1938 and which set up a jointly owned company with Ilford Ltd in 1946, called Bexford Ltd., to manufacture cellulose acetate film base (see my chronology 'slot' for 1946). Paul says "When I was in business as a photographer in the late 1960s and early 1970s, I used to get a regular visit from the Ilford "rep.", Alan Mitchell. Alan is mentioned as a source in Andy Holliman’s book 'The Cameras of Ilford Ltd'. In about 1970 I had built a water jacket to control the temperature of three 3gallon Kodak tanks that I was using to process Agfacolor paper. The tanks I was using had come from East Anglia Colour Laboratories of Caister near Great Yarmouth. In addition there was an extra one branded Ilford. I had shown the Ilford tank to Alan Mitchell on one of his visits and he told me how British Xylonite had made them. I remember the Ilford tank was narrower than a Kodak one and would not accept any of the various stainless steel racks that Kodak made, though would, of course, have taken any of the Ilford racks".

The tank lid is clearly marked "ILFORD Ltd" and "British Made" (see below - Britain was a major manufacturing nation pre-WW2 and the population were proud to purchase British made products, believing them to be superior to many foreign equivalents).


My thanks to David Muggleton for loaning me this tank so that I could photograph it and upload pictures here.




ILFORD Developing Tank in 1949

The advertisement to the left is taken from the back page of Amateur Photographer magazine for August 24th 1949. The whole page advert was devoted to Ilford Photographic Accessories, including a darkroom safelight, a dial-type thermometer, a 'Seconds' timer and the Ilford Exposure Meter Model C.

Notice that this 1949 Ilford developing tank looks near identical to the pre-WW2 tank (above), but the text no longer mentions size 117 film. The tank would probably still accept 117 as it is the same film width as No.20 (620/120) roll films(2¼" = 57.2mm), but 117 was most likely a redundant film size by 1949. What the 1949 tank is capable of accepting, is 35mm, which was becoming a standard film format by this time, though few amateurs, apart from the wealthy, would have been using 35mm in 1949. Perhaps Ilford wished to cater for their new 35mm camera, the Ilford Witness, expected to soon be in the shops, though in fact it didn't appear for another two or three years.


A tank that looks very similar to the 1949 Ilford developing tank (above), and catering for the same range of film sizes, is the one shown left, marketed by Gnome Photographic Ltd.

I owned a Gnome Universal tank such as this in the late 1950s, when my local chemist sold me an old one he still had in stock when I couldn't afford one of the more modern designs e.g. by Johnsons, Nebro and Paterson.

The only real disadvantage was that the Gnome Universal took a lot of developer and fixer solution because it was sized to accomodate a full 36 exposure 35mm film. I was only using 127, and later 120, roll film, so the volume of solutions required made it less economic than a smaller tank sized for roll film and 20 exposure 35mm.

Early Patents

The earliest GB patent relating to spiral loaded developing tanks seems to be GB320,716 with an Application Date of 20th August 1928 and a final completion date of 24th October 1929. It was filed by CLAYTON LYMAN DREW, a citizen of the United States of America, of 582, Market Street San Francisco, California, USA. The patent description includes the statement:
"The general object of this invention is to provide means whereby photographic negatives, for instance a strip of film, may be effectively developed, fixed and washed without any danger of scratching the surface of the film, and to provide means whereby a film may be wound upon a reel in such a manner as to maintain the various convolutions separated one from another.

The invention consists in apparatus for the treatment of photographic negative films comprising a container and a reel shaped member adapted to be removably positioned within said container and between the top and bottom portions of which the film to be treated is held, characterised in this that the bottom member of the reel is provided with an annular downwardly extending peripheral flange resting on the bottom of the container and both top and bottom members are provided with openings so arranged as to enable the fluid entering the space bounded by the bottom member, the flange thereon and the bottom of the container, to flow freely upwardly over the surface of the film."

DONALD MACDOUGAL PATERSON is the named inventor on 30 patents relating to photographic equipment, published between 21st November 1951 and 6th September 1977. The full list can be seen here on the European Patent Office web site (esp@cenet).

The earliest of Donald Paterson's patents relate to the inclusion of his famous 'ratchet action' to facilitate easier loading of film into the already well established film spiral used in photographic developing tanks. This patent, GB661,288, was published on 21st November 1951, but the original Application Date was "15th day of December, 1948". In this earliest patent, Donald Paterson describes the now familiar arrangement consisting of "a pair of spiral grooved plates, but instead of being rigidly fixed together the plates are arranged so that they can move independently on their common axis." However, this initial patent describes the ratchet loading of film into the spiral as being assisted by "a series of projections or teeth attached at intervals along the grooves." Although these teeth are described as "hinged or fixed, or moulded into the grooves or attached separately", there is no mention of the eventual use of ball-bearings working on inclines and held captive within small chambers at the entry of each spiral.

Interestingly, it is the GENERAL ANILINE & FILM CORPORATION who, in a patent with an original Application Date of 7th February 1948 (albeit in the USA), first make mention of the ball bearing arrangement. Their 'bibliographic data' describes a "spiral groove, of which the outer groove wall is thickened and is formed on the inside with a recess containing a ball. When a film fed through openings into the groove passes (the) recess, the ball is moved into a larger part of the recess and permits the film to move into the spool. Should the film move in the opposite direction, (the) ball is moved into the narrower end of the recess and jams the film edge against the next groove wall. By relative movement of the discs in alternate directions, the film is moved step by step into the spool." This invention was filed as a GB patent (664,162) on 21st January 1949 and was published on 2nd January 1952. Thus, although the original filing of this patent (in the US) pre-dates the first from Donald Paterson, Donald's patent was published first.

Donald Paterson's patent, GB661,356, "divided out of 661,288" has the same Application Date and Complete Specification Published Date as GB661,288 (above). This papent describes "A spool for receiving photographic film for treatment in a processing tank, comprises a pair of spaced coaxial plates rotatable relatively to one another about their common axis and each having on its inner face a spiral track defined by upstanding walls, said tracks having either their outer or their inner ends open for the insertion of the leading end of a film, and, located in at least one track, a captive roller working on an inclined plane forming one wall of the track, the upper end of the incline being towards the entry end of the track and the gap between such upper end of the incline and the opposite wall of the track being less than the diameter of the roller. Apart from the captive roller and the inclined plane, the spool is identical with that disclosed in Specification 661,288." The patent bibilography also states "Reference has been directed by the Controller to Specification 664,162." With only a lay understanding of patent law, I cannot claim to understand what legal point is made by the above "Reference by the Controller", but from a practical viewpoint it appears that the idea to use contra-rotating spiral ends together with some form of ratchet device to encourage the film along the spiral grooves, was invented almost simulataneously on both sides of the Atlantic.

Alan Meek, Technical Manager of Paterson Products until 1981, e-mailed (March 2007) to say the near simultaneous invention of the self-loading film spiral in the UK and the US was genuinely a coincidence.

"Paterson's tank at the time was for 35mm only and the film holder was referred to as a "spiral". As the backward-pointing teeth would only engage in the sprocket holes of 35mm film (Donald) Paterson wanted to create a spiral for roll film too and he came up with the idea of a ball-bearing in an inclined track. The track was a tiny moulding which was glued into the side of the spiral. As the side of the spiral was pushed forward the ball-bearing was forced into the narrow end of the incline and so gripped the film, to push it forward. When the side was spun the other way the ball-bearing moved into the wide end and released the film so that it could slide past.

Ansco (General Aniline) in the USA happened upon the same idea at essentially the same time. Their patent held sway in the USA so for the next 16 years Paterson couldn't sell their tank there, while ANSCO had no access to UK markets. After that time Paterson did begin to sell into the USA, changing the word "spiral" to "reel", since the latter word was more intelligible to the Americans.

Interestingly, Paterson used "reel" for its markets worldwide from then on, because it was more convenient to have just one package and instruction for all english-speaking markets. They changed from referring to "developing dishes" to "developing trays" at the same time and for the same reason."

This page last modified: 17th December 2014