You can't use a colour bleach as that will also remove the remaining un-processed silver halide as that you need to re-expose chemically or with light & develop to form the positive.
Our local photographic shop has a Tetenal kit for doing this. It's amongst a bunch of sale items and is going quite cheap. Does anyone have any experience of these kits?
You can't use a colour bleach as that will also remove the remaining un-processed silver halide as that you need to re-expose chemically or with light & develop to form the positive.
Ian
You're thinking about a combined bleach and fix or when there is a bleach after last developing (followed by a subsequent fix)
The bleach doesn't remove silver halide, it converts metallic silver into bromide, (ie: the developed silver from the first bath), then second developer, develops the exposed silver (which is everything, bar what was developed in the first hence reversal).
The fix wont remove the second developed silver, but it will remove the first converted by the bleach silver.
Farmer's Reducer does remove the negative image. A ferricyanide bleach followed by a sulfite clearing bath also removes the negative image. The first development should be to high contrast. After the bleaching and clearing, the second development must be to completion, and Dektol or similar may be used.
That is the process in general, but I am not an expert at using it. There are some among us who are expert, aren't there, Jordan?
A an image bleached in Fericyanide on it's own can be redeveloped even when no halide is added which is why it's not used in B&W reversal processes.
Originally Posted by Athiril
The bleach doesn't remove silver halide, it converts metallic silver into bromide, (ie: the developed silver from the first bath), then second developer, develops the exposed silver (which is everything, bar what was developed in the first hence reversal).
That's exactly what you don't want, the bleach needs to convert the silver into soluble silver salt that washes out of the image, If you convert the silver back to a bromide or chloride it will get re-exposed and re-develop with the positive.
Our local photographic shop has a Tetenal kit for doing this. It's amongst a bunch of sale items and is going quite cheap. Does anyone have any experience of these kits?
Steve.
Tetenal chemistry is extremely good, it should be worth buying.
How do I take negative BW film and develop it as a positive BW slide?
The technique is called "reversal processing" and there are dozens of threads about it here and around the Net. A search will turn up lots of useful information here.
Originally Posted by Ian Grant
That's exactly what you don't want, the bleach needs to convert the silver into soluble silver salt that washes out of the image, If you convert the silver back to a bromide or chloride it will get re-exposed and re-develop with the positive.
Agreed with Ian here -- for a bleach to be usable in B&W reversal, it must be able to completely solubilize the metallic Ag negative image without affecting the AgX positive image. This is not possible with iron(III) based bleaches, AFAIK. In practice the only commonly used bleaches for B&W reversal are dichromate- or permanganate-based.
Can you please look over this and tell me where I go wrong?
I'm going to reverse process Plus-X negative film in 16mm
First dev: HC-110 for 5 minutes
Stop bath for 3 minutes
Bleach in normal room light until it looks good (Farmer's reducer?)
Hold about 10 cm under a 60 watt incandescent light and re-expose on each side for about 30 seconds
Re-develop in normal room light with HC-110 until it looks proper
(I eventually want to try using Caffenol for the second developer)
Fix 5 min
Last edited by EASmithV; 04-21-2009 at 04:05 PM. Click to view previous post history.
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Originally Posted by Ian Grant
