Converting a Poilot 8×10 Developing Reel for 6½x8½ inch Sheet Film

This post is about modifying a Poilot 8×10 reel to work with Whole Plate 6½x8½ inch sheet film.

Whole plate is an old format from the metal- and glass-plate era. By a quirk of history Whole (and Half) plate remained popular in Japan for portrait photographers until the 1960s and 1970s, so camera equipment is available and relatively cheap because it’s not a popular format. Shanghai are making their GP3 100 film in whole plate (they seem to be making their film in every format ever invented). While there are many options for developing 4×5, 5×7 and 8×10 inch sheet film, there are no options for Whole Plate 6½x8½ other than open trays in a darkroom… until now.

Poilot is a Chinese manufacturer of film developing tanks and reels, their P2550 tanks are quality copies of JOBO 2550 tanks. Their PL-system reels seem to be their own modular design that consists of two spiral plates, three connecting tubes of different lengths and various clips for 4×5, 5×7 and 8×10 inch sheet film. Thin rubber washers are used during assembly to finely adjust the tube height to account for variations in the sheet film sizes.

To adapt the reel for Whole Plate 6½x8½ inch sheet film, the 8×10 tube needs to be shortened and have a notch and three small holes cut into one end. The size-adjusting rubber washers remove the need for precision engineering, you only need to be able to cut the tube straight and square, and make the notch and three holes in the end.

Cutting the Tube

The first step is to take the tube and remove the plastic “snap rings” from inside each end. This is fiddly and a third hand is useful at times.

Wrap masking tape around one end and draw a line around the tube 165mm from the other end. Use a hacksaw (or something similar) to cut along the line as square, straight and smoothly as you can.

The finished length of the core tube needs to be 160mm: 161mm will be OK but 159mm or less will be too short, so err on the long side. Remove the last few millimetres of tube carefully so the end is smooth and square. Ideally, use a machine cutter or sander: I used a Dremel routing tool fitted to a Dremel router table, but it could be done with a hand file if you’re good: you really need to get the end square and straight.

Cutting the Slot and Holes

Take a close look at the uncut end of the tube and notice that there is a ~3mm by 10mm slot cut in the end, and three small holes around the circumference. The slot is used to align the spiral reel ends, and the three holes are to locate the snap rings: the slot and these three holes need to be cut into the end you just shortened.

Lay some masking tape along the length of the tube in line with the slot on the uncut end, to mark where the new slot should be cut: the slots both need to be accurately in line so the reel spirals match up. The slot itself can be cut with a Dremel router, or by drilling a hole at then end off the slot and cutting/filing from the top down to the hole.

The three small locating holes around the circumference are easiest to position by wrapping some masking tape around the uncut end, marking their position, then moving the tape to the uncut end and drilling through the marks. This was the part that I had most problem with and ended up making a mess of the holes, but fortunately their precision isn’t required for success, they only need to be located so the snap ring clicks into place correctly.

When the holes are done, remove burs and plastic shavings and insert the snap rings. Assemble the top and bottom spiral plates using the rubber washers to adjust the length of the tube. I found that two rings in each end was a good starting point. Have some sheets of film on hand to test loading the reels and adjust the length so the sheets have room to fit in smoothly but there’s not enough room for them to fall out of the spiral. Finally, fit the “limiter” that is provided for 8×10 to the bottom reel, but place it one spoke inside the reel.

Loading the Poilot PL Reel

The Whole Plate 6½x8½ inch reel takes three sheets of film, and the reels are loaded with the emulsion facing into the centre of the reel.

I’ve found that the easiest way to load the PL-system reels (regardless of sheet size) is to lay the reel on its side and load the sheets from the top, starting with the outside slot. I hold the edges of the sheet on the outside of the reel and slide it down and around the reel until I feel it “click” down into the opening of the slots. The first sheet goes into the first slot; the second sheet I slide down over the first slot then into the second slot, and the third sheet into the third slots. Loading the sheets does take some practice but these reels are no harder than any other reel system I have used. As the second and third sheets are fed into the slot the centre of the edge being pushed into the reel will likely bulge out a bit and slide/jam against the sheet outside it: take care and feed it carefully, too much force could scratch the surface of the outer sheet.

All this usually happens in the dark and requires space to take the sheets from the film holders and load them into the reels. A large change bag will likely suffice for 4×5 sheet film, but larger sheets need significantly more room and a changing tent is recommended.

You’ll note that when film is loaded, the ring that holds the sheets in place from the outside only holds one side of the 6½x8½ inch sheets, not both sides, and it’s not centred on the tube. I have found that this isn’t a problem and the sheets don’t fall out with either inversion or rotary agitation.

Processing Recommendations

TLDR: for the most even and consistent development, get a roller base and use continuous rotary agitation.

I have been processing my own 35mm, 120 film and 4×5 b+w film since the early 1980s with stainless tanks and reels (using the Nikor sheet film tank for 4×5) using inversion agitation. The results with small roll film formats have been excellent and consistent. With sheet film, not so much; results have often been plagued with uneven development that shows up in broad areas of blue sky. As I moved from 4×5 to 5×7 and larger formats, the problem became worse.

After months of testing I have determined that the uneven development is caused by the long period of time needed to fill and empty the tank: the bigger the tank, the longer the fill-time, the worse the problem. The 2550 tank requires 3,000ml for 8×10 film and 2,500ml for 5×7 and this takes at least 20-30 seconds to pour in, so for the majority of the first minute the film sheets have developer dribbled over parts of them. I experimented with pre-wash and found some improvement in results, but development was still not consistent enough. (Note that Ilford specifically do NOT recommend pre-wash with any of their films.)

Ultimately I tried rotary continuous processing using a manual roller base, which typically needs only 300ml to 600ml of developer and takes less than 15 seconds to fill. This results in extremely even development without a pre-wash.

I have made a chart for the 2550 tank and PL-system reels to calculate the amount of Kodak HC-110 developer and dilution required for continuous agitation.

Note: if you watched the tube cutting video and thought “Gee that didn’t take long”… I’d already finished the reel and forgot to video myself doing it (I mean, who videos themselves doing things?) so I re-joined the cut end to the main part together with masking tape and just cut through the gap between the pieces.