Mixing half of D-76 Powder

Discussion in 'B&W: Film, Paper, Chemistry' started by Renato Tonelli, Mar 13, 2009.

  1. Renato Tonelli

    Renato Tonelli Subscriber

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    Is it OK to mix half of a package of D76 - measured exactly on a scale -?
    Is the powder mixture uniform/consistent to allow this?
    Thanks in advance.
     
  2. Anscojohn

    Anscojohn Subscriber

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    Not a good idea. Your second paragraph alludes to the reason why. Best to mix it all, then put the stock in proper smaller bottles, filled completely, and tightly capped.
     
  3. Ian Grant

    Ian Grant Subscriber

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    This question keeps being asked. The dev keeps quite well in a full bottle it isn't worth the risk of trying to split it, it may not be homogeneous. It's definitely not advisable although some people do it.

    Ian
     
  4. Renato Tonelli

    Renato Tonelli Subscriber

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    John and Ian: Thank you for the rapid response. You confirmed my suspicions.
     
  5. Vaughn

    Vaughn Subscriber

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    The best way is to mix the gallon up, then split it into smaller bottles -- fill them to the very top with a good cap and they'll last a long time (6 months in a full bottle, two months in a half filled bottle...as per Kodak).

    Vaughn
     
  6. drazak

    drazak Member

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    Renato: All powders that are mixtures are heterogeneous in nature, thusly there will be a difference in particles from the start of the mixture to the end of the mixture, solutions are all by nature homogeneous, which means the that they all have the same concentration and whatnot throughout, your best bet if you want to make up small volumes of chemicals is to get something like HC110 or PCTEA and mix it from syrup.

    Ben
     
  7. PhotoJim

    PhotoJim Member

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    An idea to consider, if you prefer smaller quantities: you can make D-76 from scratch ingredients. The ingredients keep very well (for years, at least). You need an accurate scale and a little patience, but you can make precisely what you need, no more and no less, on demand.
     
  8. BetterSense

    BetterSense Member

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    I think the "Inhomogeneous powder" angle is silly. If you are worried about it, shake the bag up or pour the powder between to containers to mix it up. As long as you can at least somewhat precisely split the powder in half either by volume or weight, I wouldn't hesitate to do it at all. I've done it with Dektol.

    But they sell 1L bags, and the stuff keeps in bottles pretty well, and you can use a concentrated developer, so it doesn't even seem worth the effort to mix up only half.
     
  9. Vaughn

    Vaughn Subscriber

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    Wear a very good dust mask if you do this! Metol powder in the lungs is not a good thing...a good way to get serious lung problems. Also, screwing up a few prints due to incorrectly mixed chemicals is one thing -- but doing the same with negatives is never a good thing.

    Vaughn
     
  10. MattKing

    MattKing Subscriber

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    For Dektol, it probably doesn't matter, because we tend to develop paper to completion. If print developer is either too active, or not active enough, we can see that, and reprint.

    For film development, there is no way to make sure that the powder is homogeneous, because different chemical components may have similar appearance, mass, and crystalline texture. You just cannot tell by looking.

    You don't want to have two batches of film developer where one batch is 10% more active than the other - unless of course you are developing by inspection :smile:.

    All it takes is one underdeveloped film, and any savings will be wasted.

    Matt
     
  11. dynachrome

    dynachrome Member

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    Mixing D-76

    To solve the problem of having to mix up too much developer at one time I suggest a solution involving two developers. For slow and medium speed films you can make up PC TEA. There is another thread on PC TEA active now. It is made up of phenidone, ascorbic acid (vitamin C) and triethanolamine (TEA). PC TEA is inexpensive and lasts a long time. It may be too grainy for some people with fast films. For the fast films you can make up D-23. D-23 is made of metol and sodium sulfite. It's easier to make than PC TEA or D-76 and a set of measuring spoons will give adequate accuracy when "weighing out" the two chemicals. D-23 is soft working and will give results which are similar to what you get with D-76. Buying powder film developers in 1 quart or 1 liter size is expensive. Buying in larger sizes may leave you with more then you can use right away.

    If you don't like mixing things yourself from scratch then HC-110 is a good choice. It lasts a long time if you mix up the working solution directly from the concentrate. Freestyle sells its own versionof HC-110 under the Kentmere name and that ay cost less than HC-110.
     
  12. Nicholas Lindan

    Nicholas Lindan Advertiser Advertiser

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    The general advice is don't do it.

    However, those who have done it report that they haven't encountered any problems.

    I haven't done it - I store commercial developer in 1 liter bottles or mix small batches as needed from scratch chemicals. I don't know the powder will keep any better than the stock solution - I have had D-76 last a year in Nalgene bottles.

    YMMV
     
  13. alanrockwood

    alanrockwood Member

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    Here's a plan. Mind you, I haven't actually tried this, so it is theoretical.

    First, mix the powder as best you can by whatever method you think is best.

    Next, pour it into a big pile.

    Next, find yourself a small spoon or scoop.

    Next, fill the spoon.

    Next, pour the spoonfull into a another location away from the pile. Let's call it location 1.

    Next, fill the spoon again.

    Next, pour it into location two.

    Keep doing this until you have several new piles. Let's say four for sake of discussion.

    Next, take another spoonfull and pour it into the pile at location 1. Now you have two scoops in location 1.

    Now, put another scoop into the pile at location 2.

    I think you are getting the idea.

    This will divide the original pile up into several new smaller piles of developer. It should produce a pretty uniform composition between the piles, even if the original pile was somewhat inhomogeneous.
     
  14. fschifano

    fschifano Member

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    Don't do it. It's not a good idea. Getting an even distribution of all the components that make up the developer may or may not be a problem, but that doesn't matter. As sold, the developer is packaged in an airtight envelope with an dry and inert gas. Once you open the package, the contents are exposed to oxygen and moisture which will start to degrade the developer in short order. It will last longer if you mix the whole thing up as directed, and seal it up in 1L or smaller bottles that are full to the brim. Do that and the developer will last at least 6 months and likely more than that. Partially full bottles don't last as long, but you should be able to finish them up before they start to go off in a couple of months.