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  1. #1

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    Can Kodak D76 be substituted for D94a by adding sodium thiosulphate?

    I read a post (not this forum) about the similarity between D76 and D94a. It said that they are very similar but that D76 is stronger. It then said to get something like D94a, to add 1L of a 10% solution of sodium thiosulphate to 1L of the D76. I'm no chemist but I looked at the two formulae and thought that they looked a bit different in terms of relative quantities of components.

    Simply put I want to try d94a for tri-x reversal processing but I cannot go through the process of mixing it from scratch at home. I thought that adding sodium thiosulphate to some D76, would be within the scope of my knowledge and resources, though. And I'm also dead keen on sticking to a potassium permanganate based bleach which I believe fits in with the sodium thiosulphate in the dev.

    Any view on a simple path to D94a, please?

  2. #2
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    Henry, the formula for reversal 1st developer calls for adding some sodium thiosulphate to clear highlights but Mr Datsuns recipe in the OP seems way excessive.

    Sorry I'm also unfamiliar with D94a

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    Quote Originally Posted by brucemuir View Post
    Henry, the formula for reversal 1st developer calls for adding some sodium thiosulphate to clear highlights but Mr Datsuns recipe in the OP seems way excessive.

    Sorry I'm also unfamiliar with D94a
    You mean a 1L of a 10% solution is excessive? That's just as I remember reading it. I see that D94a has Sodium Sulfite (anhydrous) 60.0 g in it. I'm a bit out of my depth with chemistry.

  4. #4

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    The first developer for a BW reversal process usually contains about 6 g/l of sodium thiosulfate to clear the highlights of the slides.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  5. #5

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    Quote Originally Posted by brucemuir View Post
    Henry, the formula for reversal 1st developer calls for adding some sodium thiosulphate to clear highlights but Mr Datsuns recipe in the OP seems way excessive.

    Sorry I'm also unfamiliar with D94a
    brucemuir, If we assume that 10% means W/V then doesn't it look like a reasonable amount as by the the time you add 1L of it to 1L of D76 you have 5% W/V of sodium thiosuphate?

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    Gerald, Thank-you. So what I need to work out now is whether D76 is similar enough to D94a once the sodium thiosulfate is added to produce similar results? I'll find the formula and post them.

    Kodak D-94A

    Water, 50 degrees C (125F) 750ml
    Kodak ELON (Metol) 0.6g
    Sodium Sulfite (anhydrous) 60.0 g
    Hyrdoquinone 20.0 g
    Sodium Bromide 7.0g
    DTOD 0.42g
    Sodium Hydroxide 20.0 g
    Water to make 1.0 L

    afaik, DTOD is the hypo for which we use the sodium thiosulphate.

    Kodak D76

    Water 750ml
    Metol 2g
    Sodium sulfite (dessic) 100g
    Hydroquinone 5g
    Borax 2g
    Water to make 1000 ml

    how does that look? Are the two similar enough? The quantity of Hydroquinone are quite different.

    I'm trying to get a result as like D94a as possible because I like what i've seen.
    Last edited by mr.datsun; 02-07-2013 at 04:13 AM. Click to view previous post history.

  7. #7

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    The differences in the formula make the differences in the action of the developer : D-94 is a high contrast developer well suited for bw reversal whereas D-76 is a rather low contrast developer, thus not well suited for bw revereal.
    In effect, the amount of hydroquinone which is responsible for high densities on the film, is too low in D-76. What's more, there isn't any sodium hydroxide, which as a strong alkaline buffer removes fog strongly and contributes to high contrast. So using D76 you will end up with a grey positive.

  8. #8

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    Quote Originally Posted by Tofek View Post
    The differences in the formula make the differences in the action of the developer : D-94 is a high contrast developer well suited for bw reversal whereas D-76 is a rather low contrast developer, thus not well suited for bw revereal.
    In effect, the amount of hydroquinone which is responsible for high densities on the film, is too low in D-76. What's more, there isn't any sodium hydroxide, which as a strong alkaline buffer removes fog strongly and contributes to high contrast. So using D76 you will end up with a grey positive.
    Tofek, thank-you. That's a very clear explanation! So I guess D94a has to be mixed from scratch? I'll stick to PQ Universal for the time being. I have ordered some sodium thiosulphate to add to it.

  9. #9

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    A good alternative to D-94 is the high contrast developer D-19, which you can buy, and add thiocyanate (or thiosulfate) if you want. On this site there is a comparaison of developers tested on Tri-X (see 'research') : www.super8.nl

  10. #10

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    Here are Ilford's instructions for reversal processing.

    http://www.ilfordphoto.com/applications/page.asp?n=90
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

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