If 3% peroxide works, there's no reason to spend money on stronger -- or deal with higher hazard level of handling it.
Well my thinking was twofold:
1. I have to order 3% online (currently from the UK... but Brexit) because I can't get it at the pharmacy in an amount more than 150ml. So being able to dilute down 9% that I can buy in town would be nice.
2. I am still hoping there is a way to run it at room temperature and since the paper reversal experiments in 9% seem to run at room temp, I thought maybe this would also.
But, I agree, working with 3% is easy and not dangerous at all. Very little risk of bleaching your clothes as well.
I can get 3% at the local grocery for US$0.89 per liter.
Yes! So much easier in the US.
I've got a bottle of 75% strength acetic that I bought for making stop bath (and then promptly found my old bottle of Indicator Stop Bath concentrate, as well as a still-good jug of working solution). Sounds like time to shoot a roll or two of some B&W film or other and try this again -- I didn't stay interested in it originally because of the dichromate and battery acid.
That acetic acid will mean you can easily experiment with more or less dilution without also adding a bunch of water like I would by adding more vinegar.
Can you write up your exact process -- dilutions, times, and temperature for each step? So we have it documented for future searches?
Yes, I will! Shortly.
1. Would more quantities vinegar spoil the process?
I experimented with this a bit while testing out percarbonate bleach. I have not yet adjusted this variable much with the peroxide. This remains to be established!
2. Are you sure you want the bleach to happen under daylight? Don't you run the risk of solarizing the film?
When I say daylight I simply mean diffused window light/room light. You don't want direct sunlight. Bleaching in the light allows you to do it by inspection and that's pretty useful.
3. I understand that the second development could be done under light too, are you developing by inspection? Supposedly the development should be done to completion in this phase.
You need to fully stop the first developer and then from that point on you can do everything in the light without issue. Yes, the second developer needs to run to completion, so there's no advantage to developing in the light. It's more convenient for me to put the film back in the canister at this point and develop as normal.
As far as halide solvents in first developer are concerned, if IIRC David has in this forum itself said that his process doesn't use them.
Good data point!
I think the ideal EI is between 200-400 for this film and if one goes higher than that slides look darker but with corresponding loss in shadow details. If at this EI you're getting light slides, then you're probably overdeveloping and/or fog is too high.
It's probably worth experimenting with the first developer time. I can say that at EI 400 it looks very good, very good shadow detail. When I shoot as a negative I have to use EI 200, and by EI 800 it's a disaster. So the developer is definitely picking out more in the toe than XTOL stock.
It's not the case that the film becomes more sensitive to light in reversal processing. A high contrast first developer might be able to tease out a bit of shadow details from the toe but it usually is accompanied by a corresponding increase in the fog level. It is the high contrast index of slides that gives credence to claims on speed gain though uprated slides typically loose shadow details.
Well sure, I'm not claiming the film is more light sensitive. But Foma's own datasheets show that the EI of the film varies widely in different developers. Given the other scenes I shot, I'm going to use EI 400 and see how it goes.
To find out the EI of a film for reversal processing, a sensitometry study like what @iandvag did for Ilford Delta 100 is required. In the absence of it, a simple test would be something like this: shoot a uniformly lit textured white surface at -2, i.e. by placing it in Zone 3, for each of the proposed speed, say 200, 250, 320, 400, 500, 800, 1000 in the case of Fomapan 400. The highest speed which shows full textural detail in the corresponding slide is the one to be used as EI. Anything higher than this speed may give "acceptable" slides but with loss of shadow details.
Very good info. I don't have a densitometer (yet!) so I can't do anything like the detail that
@iandvaag did. But I will try to find some time over the holidays to attempt this test with a film that I actually like. Fomapan 400 is just my experimenting film because I accidentally bought 100 feet back when Arista Premium (Tri-X) was available and I ordered the wrong thing. I have about 10 rolls left. If I do an extensive test it will be on Silvermax 100/Scala 160 since I have 200 feet of it.
Thanks all for your support!
These the first two images are from the scanner, in grayscale mode. To show the neutral gray of the reversal, the 3rd picture is a photo of the slides on a makeshift light table. I think they are a little dark in general, which implies that an experiment with thiosulphate in the first developer is a good idea.
