But, I wrote to Wolfgang Moersch about getting ahold of HEDP/editronic acid and we'll see if I hear back. Unless @Lachlan Young knows how to buy direct from Suvatlar that seems like the only reasonable route to get it.
Thanks!!I keep forgetting that Moersch's German pages often have more detail than the English ones - Moersch gives a direct email for Suvatlar - fotosuvatlar@live.de
Moersch also states that you should order direct from Suvatlar unless you want to combine with an order of Moersch materials to save shipping costs.
Thanks!!
Wait what is that chemical and how does it increases the shelf life of permanganate bleach?Here's a link to Suvatlar's 2021 pricelist too. I need to see if he can supply some nitrilotriacetic acid.
Item Nr.40 is what you want to get acidified permanganate bleaches to last.
Wait what is that chemical and how does it increases the shelf life of permanganate bleach?
Here's a link to Suvatlar's 2021 pricelist too. I need to see if he can supply some nitrilotriacetic acid.
Item Nr.40 is what you want to get acidified permanganate bleaches to last.
Some update on my EDTA experiment:
I added various amount of EDTA to the phthalate-peroxide bleach. Interestingly this seemed to increase the rate of bleaching and reduce staining. Blistering is also reduced.
I see some stain-reducing effect of EDTA on acetic acid-peroxide bleach too. Hopefully we can formulate some usable peroxide bleach with EDTA or HEDP.Interesting results! Looks like the ugly brown stain was also cut down by the addition of EDTA. Last strip, one that used highest amount of EDTA in your experiments, looks the cleanest.
This formula works much slower, probably due to lower hydrogen peroxide concentration.
ThanksYou may want to use this particular bleach 24 hours after preparing as peracetic acid formation is not instantaneous and there's a study that shows that even at higher concentrations of peroxide and acetic acid, the reaction takes a few hours to produce useful amounts of peracetic acid.
I bleached a strip of film with dichromate bleach for comparison. Looks like both peroxide bleach cause slight sepia staining.
ThanksI might try the peracetic acid version to compare.
Thanks for pointing out the stain removal bath. I have completely overlooked it when I first read the patent. The stain removal bath look like some sort of rehalogenising bleach. Maybe the stain is caused by unbleached silver?Konica patent has a stain removal bath after second development, IIRC. Maybe a short bleach in dilute Ferricyanide followed by fixing will can remove this stain.
I have seen reports on phthalic acid and its derivatives for stabilisation of hydrogen peroxide. I guess potassium hydrogen phthalate probably has similar stabilising effect?Also interesting is the role played by PHP. Apart from acting as a pH buffering agent, is it also working as a stabilizer for peroxide?
Thanks for pointing out the stain removal bath. I have completely overlooked it when I first read the patent. The stain removal bath look like some sort of rehalogenising bleach. Maybe the stain is caused by unbleached silver?This is interesting and I will try if flexicolor bleach can remove the stain.
This is interesting and I will try if flexicolor bleach can remove the stain.
Konica patent has a stain removal bath after second development, IIRC. Maybe a short bleach in dilute Ferricyanide followed by fixing will can remove this stain.
I would guess even a dilute Farmer's reducer would work well for this purpose when used after the second developing of the film.
I have seen reports on phthalic acid and its derivatives for stabilisation of hydrogen peroxide. I guess potassium hydrogen phthalate probably has similar stabilising effect?
You should definitely. BTW this is already looking promising, at least for the film you tried it on. Good work.
If HEDP/EDTA can be substituted by Calgon (sodium hexametaphosphate), it'll be even more useful for some people who don't have easy access to the former chemicals.
Calgon-Photo is Sodium Hexametaphosphate - regular Calgon used to be the same, but then changed to a different formulation - and it acts as a manganese sequestrant in acidified permanganate bleaches, making them last for much longer. It's one of these ingredients that often gets dismissed as being 'for water quality' when seen in an ingredients list, but there's an Agfa patent (EP1006408A1 - only in German as far as I can tell, apart from Google's automatically translated version) which shows that 20g/l is about optimal for preventing the manganese deposits appearing & extending the bleach life into weeks.
Interesting, this is the free acid, not a Na salt. This is very useful to those who would like to scratch mix some E6 bleach, combined with some ammonia, ferric nitrate and ammonium bromide.FYI if anyone is trying to buy EDTA in Europe, this is the place in Ireland that I got it: https://mistralni.co.uk/products/edta-ethylenediaminetetraacetic-acid-dissolvine-z
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