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Thread: HYDROQUINONE

  1. #11
    Athiril's Avatar
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    The price rose massively here some time ago, over a year ago iirc.

  2. #12

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    Quote Originally Posted by Gerald C Koch View Post
    You cannot just substitute ascorbic acid for hydroquinone. As has been stated many times on APUG the resemblence between these two chemicals is only superficial. Xtol is probably the closest ascorbic acid analog for for D-76 after all the correct adjustments to the formula have been made. Search on APUG for the formula which has been posted on more than one occasion.

    There is also the Haist modification to D-76 which eliminates the hydroquinone and increases the metol content slightly. It is referred to as D-76H and is used just like D-76. Note that the name uses a captal H since there is another completely different version of D-76 referred to as D-76h.

    D-76H

    water (125°F) 750ml
    metol 2.5g
    sodium sulfite (anhydrous) 100g
    borax (decahydrate) 2.0g
    water to make 1 liter


    The version above is used as a one shot either FS or 1+1.
    hi gerald


    this is kind of like split d23 ( dd23 ) or one version of it,
    but mixed together ..
    i had heard years ago that when mixed together it was pretty much like d76 ( or one of its variants )
    thanks for posting this !

    john
    if my apug gallery looks empty you might check these places

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  3. #13

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    Hi Michael,

    I know that you would not advocate a simple substution. I was answering Bob C's post which appearred to ask just that question. I also wanted to post D-76H as a remedy to the cost of hydroquinone. Since there is nothing to regenerate the metol as it is used up this version cannot be replenished. Looking back I was probably a bit rude to reply since Bob's question was addressed to you. My apologies.

    Jerry
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  4. #14

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    Hi John,

    I have used D-76H in the past and the results appear to be identical to those of D-76. This formula also points out that at the low pH of D-76 the main purpose of the hydroquinone is to regenerate the metol as it is consumed. This can be seen from the rather small adjustment to the metol to compnsate for the lack of developing activity from the hydroquinone.

    Jerry
    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. #15

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    Quote Originally Posted by Photo Engineer View Post
    There is a thread on this here on APUB about 2 months ago.

    PE
    APUB? PE, have you been drinking or got drinking on your mind?
    Bob Walberg

    The fix is in!

  6. #16
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    Thank you both

    Quote Originally Posted by Michael R 1974 View Post
    I was not suggesting replacing HQ with ascorbic acid in any formula. I've stated many times on here I do not believe in simple substitution formulas. Once something is changed, the entire formula needs to be looked at and possibly rebalanced, or scrapped.

    Bob - the formula Gerald posted for the Haist version of D76 (D-76H) is correct. The formula is the same as D-76 except the HQ is eliminated and the Metol is increased to 2.5g. Image characteristics are said to be virtually identical. As for its capacity compared to regular D-76, I cannot say.

  7. #17

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    Quote Originally Posted by Bob Carnie View Post

    could you post the formula for D76 without HQ?
    I read somewhere that DK-76b is an official Kodak formula without hydroquinone, but I could be mistaken.

    http://www.digitaltruth.com/data/dk76b.php

  8. #18
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    Quote Originally Posted by walbergb View Post
    APUB? PE, have you been drinking or got drinking on your mind?
    Drinking? Not that early. Just an error while touch typing, one that I missed.

    PE

  9. #19

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    Quote Originally Posted by Gerald C Koch View Post
    Hi John,

    I have used D-76H in the past and the results appear to be identical to those of D-76. This formula also points out that at the low pH of D-76 the main purpose of the hydroquinone is to regenerate the metol as it is consumed. This can be seen from the rather small adjustment to the metol to compnsate for the lack of developing activity from the hydroquinone.

    Jerry
    Hi Gerald, sorry about that I must have been in one of my moods when I was reading the thread...

    Indeed it seems in many low pH, dual-agent fine grain developers there is functionally one primary agent doing the direct development (Metol in the case of D76) while the secondary agent's function is to regenerate the primary agent. In the case of MQ developers like D-76 as you point out the pH is too low for HQ to be active enough as a primary developing agent.

    Interestingly this appears to be the case with modern Metol-Pyrogallol developers too, where the working pH (below 10 in the cases of both WD2D and PMK) is too low for Pyro to do much direct developing.

    What is your take on XTOL though? At its working pH it would appear the Phenidone derivative is the direct developing agent and the ascorbic acid regenerates the Phenidone. However I remember reading that Zawadzki believed the ascorbic acid was the primary developing agent. That might have been a misquote though.

  10. #20

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    Quote Originally Posted by Photo Engineer View Post
    Drinking? Not that early. Just an error while touch typing, one that I missed.

    PE
    Come on PE, we wouldnt blame you for hitting the sauce early and hard. Watching your former company sink almost daily has got to be rough. My last company was bought out by a competitor and essentially shut down. That was a brutal experience that was very hard for me to take, even though I only worked there 6 years. I can't imagine what it would have been like with 20+ years.

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