I have mentioned it to Oli, but please also flag every spam post as well.

That's an interesting idea for drying prints!

There’s nothing that immediately stands out. Normally exhausted developer is the prime suspect for staining, but given you have made an acceptable print earlier in the day that is unlikely. Exposure of the developer to air will cause oxidation and that is observable by a change in colour, and would be accelerated by agitation during transport over several days The type of image could affect the result. Assuming you are using Positive Paper, if it was over exposed the print will be light so there is less work for the developer, but more work for the fixer to do to remove all the unexposed silver halide. Conversely if the Positive Paper is under exposed the print will be dark and there is more work for the developer, and less for the fixer to do. Other factors to consider your agitation technique, excessive time/exposure to air between the development and fixing steps, insufficient fixing, or contamination - A very small amount of fixer in the development process can cause staining. Consistent and uniform agitation will help ensure all areas of the print receive equal or as close as possible exposure to the liquid. Insufficient agitation can cause streaks and uneven patches. I have the original bottle of Dev (or Fix), and apart from making up the diluted solution, that never moves. I have a lots of concertina bottles that holds the diluted solution to exclude air, and that sometimes travels with me if I have a base/car to leave them. Then I have small travel bottles that I refill daily – these I’d only take enough for the expected number of prints I was going to make, plus maybe a few extras – so these would be maybe half full and I’d discard this daily. High temperatures over 40-50c can cause chemicals to break down. Preloaded, and full syringes can minimise delays. You can fit 22ml if you carefully pull out the plunger. If you consider the amount of actual developer in a syringe (before dilution) it’s tiny 4ml at1:5 , so every extra ml counts. Sometimes I might take 2 sets of (3) syringes (in a Pinsta syringe dock) instead of a small refill container. I’d also suggest both developing and fixing longer, and not reusing fix. Try 3 minutes assuming 20c, and keep the process between 14-24c. Often I make up my solutions to half strength, then add the extra water from a flask to control the temperature.

Please can you give more details about your process. I think the developer is exhausted, which causes the staining. However there are many reasons why a developer can degrade. How old is the developer, and do you carry the original bottle around with you, or do you make up a quantity and carry that with you, leaving the original bottle at home? What volume of developer are you making up at a time, what temperature is the water you use to dilute it, and how many times do you use a syringe of developer? When you use he developer, how much is going in, and how much do you lose - a full 20ml in, and ? ml out? What steps are you using - dev, fix, wash? How long are those steps? Are you cleaning the internal camera area each time? Are the prints that fail made at the same time as those that are ok?

Yes, it works well. You'll need to do some tests for the paper speed. I have a Multi grade paper that is iso 6, and a Graded Paper that is iso 1.5 . The paper has a wider latitude than Direct Positive, so that's nice as it's more forgiving, and it's cheaper. You can then use a free app such as Snapseed to invert the result, print it (hopefully no brands names are written on the back of the paper), or reverse it - Martjn wrote a blog about that.

To convert f/ numbers divide the Pinhole f/ by the Lightmeter f/, and Square it. (The standard pinhole for a Pinsta 4x5 is f/229 (229/11)^2 = (20.8)^2 = 433 Multiplication Factor f/ To Convert Iso divide the Lightmeter Iso by the Paper 100/2 = 50 Multiplication Factor i To convert your Lightmeters calculated exposure just multiply those two MF's For example 0.5 sec x 433 MFf/ x 50 MFi = 10825 sec = 180.5 minutes. Rounding by a few seconds at this length of expsoure isn't going to make any difference. If you use film, you must take into account Reciprocity Law Failure, this is not required for Direct Positive Paper. If you want a more detailed explanation, see my profile Instagram https://www.instagram.com/p/CygWQ1SSZVW/

Personally, while it is possible to reuse chemicals, I don't for consistency reasons. If, for example you are using Multigrade Dev at 1:4, that's only 4ml of Dev per syringe, which isn't much to start with, and even less active component on subsequent prints when you take into account the amount of liquid absorbed by the emulsion, and used during development. However you are more likely to get favourable results, if the prints are light/high key so the developer has less work to do (but the Fixer will have more work to do, especially when the amount of Dev carried over for mutiple prints is taken into account). Both exhausted Developer and Fixer can cause staining. Given a syringe is only 20ml (22ml if you pull it the the max), I use fresh chemical each print each time, but I have on occasion reused 2 or 3 times when I was travelling light and only carried a very small amount of chemicals, topping up the small amount lost. If I lost more than a few ml of Dev, I would use fresh Fix the next time. By the 3rd time, the Dev looked pretty bad, so I don't consider this to be worthwhile, given the cost of the paper vs the cost of the chemicals. I don't know if anyone has produced a table for extended develment times, but if you look at Ilford's Simply Range for reusing 600ml of Dev for 2 x 500ml processes, it is to use 500ml the first time, remix with the remaining 100ml, and use 500ml and extend by Dev times by 10%. So if you want to try that, top up, extend times, and observe the results.

If you want to get an idea of UK exposure times, take a look at my Instagram (link in the Pinsta profile) - I'm in the UK - London. I have all of my exposure details on each post, and how I calculated the adjustment in exposure from a lightmeter to a pinhole. There's no digital editing - curve correction on any of my images. Generally I prefer to take photos on an overcast day instead of a bright sunny day, as there is less contrast. The only time I wouldn't bother is when using Positive Paper within a few hours of sun set, as the constantly decreasing amount of light continually increases the exposure time, which is a real pain when the exposure time is long already. You can use a Lightmeter app on your phone if you want to see what sort of times you'll get before buying. Set it to f/229 and 24mm (for a 35mm camera). If I had more time (and perhaps more money) I'd go old school and use an exposure chart such as the the Ilford Exposure disc (see Pinsta links) Temperature won't make any difference to the exposure, but it will make a difference to the development times. Martjn's idea of using a hotwater bottle in your kit bag is quite a good tip. I use a flask of warm water to add to my chem's, and use a temperature chart to adjust development times - ideally try to keep developing liquid temperatures between 13-24c and adjust times accordingly.

A print will darken to a small extent. As the emulsion dries, the swelling reduces, and causes the print to darken, you might also notice it sharpens as well. This is more noticeable on fibre paper, which Direct Positive is, than on resin coated paper. To rule out incomplete fixing, can you give some details on your fixing process, and/or can you post an example photo?

There's always a risk of the Dev affecting the Fix. I think less so for uneven development as even if you used a Stop, the flow of the liquid over the paper would be the same regardless of whether it was Stop or Fix. So if you were to get uneven development - perhaps if you were undeveloping for example, it would be uneven either way, so for me, it's just a consideration of the effiency of the Fix. In all my years of developing, I've always used a Stop (and still do for roll film on a spool), however it does work - you can thank Oliver for coming up with the concept of using the least amount of chemicals possible. The proof of the pudding is in the eating, and I haven't noticed any undesireable results, I'll let you know in 50 years about archival storage. If I was to be concerned about any steps, it would be to increase the final wash to either several syringes of water, and/or a wash baths. If you are concerned about it, just do what you are comforable with. I did previously suggest to Oli to make some 4 dock (5 might be a bit too big) syringe holders for anyone that wanted to include extra processes, whether it was Stop, a 2 stage Fix, or 2 stage Wash or whatever. If enough people ask, perhaps he'll make one if there's enough demand.

It certainly doesn’t hurt to use a rinse or Stop process between the developer and fxer, however plenty of people don’t use one without any noticeable effects. Just to review why people might use a rinse or stop process: A water rinse only slows development, it does not completely stop development as developer remains in the emulsion, however it does remove a lot of the contamination so it does slow development, and reduces the effort required by the fixing stage. A more effective technique would be to use a Stop, which neutralises developer and therefore is not carried over into the fixer, preserving the useful life of the fixer. However a few considerations that you might want to pay attention to are - trying to extract as much developer as possible, using fresh fix each time, the amount of exposure as a darker print has less unused silver halide to be removed (that's not a exposure suggestion) , and/or increasing the duration of the fix process.. Using exhausted fixer can cause staining. If you were really worried about it use a two syringe process, where the second is a new batch and after a while rotate that forward to become your first fix. If you are concerned about continued and uneven development, you can review the calculated time of development, more so for film, and how long it takes to remove/replace chemicals, and dilute/slow things down. I don’t use a rinse or Stop including on 4x5 sheet film and 8x10 paper in the Pinsta, perhaps if I was reusing the fix, or a larger amount, I would consider it, but I do pay close attention to the amount of residual developer.

I'd be inclined to say an incandecent type would be better, I think a lot of these replacement fluorescent or LED types, take a while to reach maximum brightness, and also exhibit an afterglow after being turned off, which could make for a inconsistent exposures. I don't know about those bulbs you mention, but if you already have them it's worth trying them, but they sound like they are bright, which isn't ideal for short exposure (unless you have a control timer). Initially go for a really wide exposure test strip, double each time/step for example 1, 1, 2, 4, 8, 16 , 32, 64, 128 etc seconds covering up as you go. (For any in camera test strips, use the diffuser, otherwise the pinhole is capable of resolving the pattern of the light source).

You’ll need to make a test strip, that’s the only way you can be sure for your set up/distance/bulb strength. Personally I’d use a low power bulb, that way if you need to shorten the exposure you can, otherwise you might struggle to make accurate exposures using a simple switch. You could also increase the distance between the bulb and frame. If you can measure the distances, you can calculate the expected change in exposure. Review the Inverse Square law https://en.wikipedia.org/wiki/Inverse-square_law You can dilute, and personally I prefer to, but consider how much actual developer is in the solution you make up. So unless you are tray developing where there is more volume and therefor a greater amount of the active components, don’t dilute too much. Temperature is also a consideration as to the speed of development.

I think the fixing stage is incomplete. Either it's too short, or exhausted.

Yesterday, I was really struggling to remove 4x5 film. In the end, it came free easily after I used a full (water) syringe to inject rapidly into one corner (with the back removed).

If the remaining 450ml changed colour in 10 days, without any movement, I'd be inclined to still use it. An indication that it's exhausted would be the inability to reach maximum density - black, upon development. Increasing the development time, and/or reducing the dilution might help.

Can I ask how you are storing/using the developer, and how much developer is in the bottle? For example do you carry the opened bottle of developer around with you, and extract the required amount of developer (2ml for 1:9 in a 20ml syringe) as and when required, and then top with 18ml of water? The change in colour is caused by oxidation, which will be increased with agitation of the bottle. You can of course still use it, but the amount of development will be reduced, and given the relatively small volume of the syringes would be a risk. Personally, I split my 1 ltr dev into 2 x 500ml bottles, to keep one fresh whilst I use the other. Those don't travel anywhere. I also make up a working solution 1 ltr 1:9 and keep that in concertina bottle, so that I can reduce the air space down (that would be perfect for the main developer, but the smallest I found was 1ltr collapsing to 500ml), this lasts me months - that's 50 shots before I have to worry about airspace under 500ml, and would dispose of it if it showed more than light yellowing. I also transfer enough diluted developer to the Pinsta transport bottles which hold 100ml - 5 shots worth of additional solution. If I have travel anywhere, like a holiday, then I take my diluted solution in the concertina, and the Pinsta travel bottle. My main dev bottle, doesn't go anywhere.

I do a lot of experiments on the Pinsta, and it's not something I've had happen to me. If it's not the pinhole shutter on the front, which you ruled out (insert top left of mine as a comparison, ignore the yellow ring, that's just me colour coding my pinhole sizes), then I'm thinking that the pinhole holder inside is not fully inserted, creating an obstruction. You can check that by opening the holder (main images and bottom left) by twisting it anticlockwise, about 30-40 degrees and lifting it out. You might need to get your finger nail underneath it. The holder should be pushed all the way in, so that there is no gap between the body and the holder. If you want to check/remove the pinhole, after you removed the holder, close everything up/put the back on, and push the pinhole out from the front with something soft - a piece of rolled up tissue etc. That way you know the pinhole is still inside the body and not dropped out, and then spend ten minutes looking for it (don't ask me how I know that). It will probably be stuck on one on the magnets when you reopen the case.

Are you preflashing?

How are you determining the duration of the flash? If you want the short answer (as you are using a torch and are probably unable to increase the intensity) try increasing the duration of exposure, further exposure would be expected to reduce the maximum density for HDPP (or increase the minimum density for normal paper), and change the exposure range.