calibrating scales, mixing chemicals, fixer life?

Discussion in 'B&W: Film, Paper, Chemistry' started by eddie gunks, Feb 7, 2008.

  1. eddie gunks

    eddie gunks Member

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    hi all,

    i just began mixing my own bulk chemicals. i have been reading all kinds of info and my head hurts a bit. :smile:

    how do you all calibrate your scales? i have an old triple beam that i am using but i am not sure if it is anywhere near correct. i heard a long time ago that a nickel weighs 5 grams. can anyone verify that?

    i have sodium thiosulfate that i am making fixer with. this is pretty much a one use fixer correct? i enjoy using my kodak fixer that i can re use until my fixer tester says it is bad. can i mix something like the kodak fixer? what is the receipe? something that i can re use several times? sometimes i just do not want to mix chemicals first, i just want to begin developing.

    so far that is all i can think of. i usually think of more as soon as i post.....

    thanks for the help.

    eddie
     
  2. jim appleyard

    jim appleyard Member

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    I can't help yoou with the scales, as I use the teapsoon method, but a sod. thio based fixer can be made to be re-used.

    Some really good reading is Anchell's "Darkroom Cookbook".
     
  3. Tom Hoskinson

    Tom Hoskinson Member

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    Eddie, Google the US Mint Coin specifications: According to the US Mint Specs:

    A US Nickel weighs 5 grams

    A US Dime weighs 2.268 grams

    You can also buy sets of calibration weights.
     
  4. Murray@uptowngallery

    Murray@uptowngallery Member

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    Don't use any coins as old as your cameras/lenses/etc...they're probably worn thin! :surprised:

    jackspcs.com has some recipes
    apug has some somewhere too
    I think even digitaltruth site might too
    heylloyd too
     
  5. Monophoto

    Monophoto Member

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    I bought an electronic scale a couple of years ago. The manufacturer offers a set of calibration weights that cost as much as the scale, but the instructions suggested that using a nickel could also be used and confirmed the 5g weight.

    However, it would seem to me that it would be a good idea to standardize on one nickel - find a new one (I would expect the actual weight to diminish with several years of circulation), and set it aside for use as THE reference.


    Hell of a lot cheaper than buying calibration weights.:smile:
     
  6. rwyoung

    rwyoung Member

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    The EXACT ABSOLUTE weight isn't terribly important for calibrating your scales. So long as you always use the same scale and the same calibration weight (nickel) the you will be CONSISTENT in your measurements. Once you have standardized your scale, always use the same procedures and your formulas will be consistent from batch to batch.

    This isn't to say you should be using a 12g mass as your 5g calibration weight. You should try to be close to 5g when working.

    As to the hypo, you can re-use it but its capacity is less than the package stuff. Same test solutions work I believe or you can count sheets/rolls.
     
  7. Murray Kelly

    Murray Kelly Member

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    Very little in photo brews needs as much exactitude as your scales can provide. Your guesses at exposure will be of greater magnitude than differences in developer variances.

    Mostly the only certitude is the developing agent itself (eg phenidone, metol etc.). Lots of folk work with teaspoon amounts and get perfectly repeatable results.

    Put a container on the scales and note the weight. Add 100 ml of water and you will see, most likely, a change of some number which is equivalent to 100g. If it isn't 100 on the scale you will have to work around that number you see as being 100g.

    The 100 ml water is from a calibrated beaker or 10 fills of a 10ml syringe from the pharmacy.

    I would wager that all it needs is is something to establish the 'zero' point and everything will fall into place. Result = happiness. :smile:

    Murray

     
  8. Kirk Keyes

    Kirk Keyes Member

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    "Calibrated Beaker" - I've worked with a lot of laboratory glassware and I can say that calibrating a beaker would be kind of pointless. The lines on beakers are typically only +/-5%. You want to use glassware that is "volumetric" - i.e. designed to measure precise amounts.

    I would look on the bay and find one of the "gem" scale dealers that offers calibration weights. A 50 or 100 gram one should be fine for checking your scale. They should not cost more than a few bucks.
     
  9. CBG

    CBG Member

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    It doesn't matter whether your measurement equipment is perfect or not as long as you have repeatablility. Even if your scale has, for example, a 10% error, your process can take that into account. What you want is for the errors to always happen the same. It will still work fine.

    Here's how. (Note that you don't want to use volumetric measurement when you can reasonably avoid it. Weigh everything practically possible that goes into your chemicals. Especiallly compounding developer.) Lets assume your scale reads too high so you end up with 9 grams when you think you are getting 10 grams. That's fairly unlikely but would not be a big problem. If you have 10% too little metol in 10% too little water - your strength of solution is still exactly right. You just have a bit less of it than you thought. What you want is repeatability.

    Even if somehow, your developer is a bit weak, you will eventually start using a longer developing time to compensate, or modifying the formula to get a bit more rapid action. Once you have consistent results, you can start "tweaking" the process to improve it.

    Best,

    C
     
  10. dancqu

    dancqu Member

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    [QUOTES=eddie gunks;584585]
    "hi all: how do you all calibrate your scales? i have an old
    triple beam that i am using but i am not sure if it is
    anywhere near correct."

    I've a beam balance on the shelf. Switched to an electronic;
    much more convenient and quick to use. Mine is an Acculab
    with 0.01 gram resolution and accuracy, 200 gram capacity.
    Consider such a purchase. With Home brewing capacity
    need not be so great as fresh chemistry is close at
    hand.

    "i have sodium thiosulfate that i am making fixer with.
    this is pretty much a one use fixer correct?"

    Check out TF-2 or A. Adams S. Thio. fix. Both reusable.
    But don't knock fresh fix. The only way I use it; very-dilute,
    one shot. Also those solid concentrates don't go bad. Take
    a long time out and your chemistry will still be good.

    My session of printing to be done is determined ahead and
    both developer and fixer are compounded accordingly. Same
    for film. Nothing goes back into the bottle. Dan
     
  11. gainer

    gainer Subscriber

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    I don't see the point of worrying about a triple beam balance. Worry about the weights. You might worry about the slider, but the scale it slides on surely hasn't changed. How much of the slider could have been worn off over the years? If you can set the tare adjustment so that the balance balances with the slider at 0, go ahead and weigh a coin, but you will probably find it still weighs the same as it did when the balance was new. I suppose there could be some wear or corrosion of the knife edge, but you would see that as hysteresis.

    Mke sure the balance is close to level when you use it. You can change the balance point by moving the tare weight or by raising one end or the other of the base. I leave it to you to discover which is better.

    If you want 0.01 gram accuracy, you don't want a triple beam balance.
     
  12. Wanted Zone vi 8x10

    Wanted Zone vi 8x10 Member

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    Scale issues

    I use a scale that is digital and measures to about 1/100 of an ounce. These scales cost about 20 bucks. The actual measurement it reads is in tenths of a gram. If I tear off a piece of paper the size of my thumb nail it will register. Thats probably the easy way to weigh chems.
     
  13. Phillip P. Dimor

    Phillip P. Dimor Member

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    Penny Standard weight 2.5 grams
    Nickel Standard weight 5.0 grams
    Dime Standard weight 2.268 grams
    Quarter Standard weight 5.670 grams

    I can tell you from personal experience that some pennies come out at 2.4, some nickels come out at 4.9. It varies a bit but that variation won't kill you. Phenidone I believe is what you want to meaure correctly. Otherwise there is room for error IMHO.
     
  14. eddie gunks

    eddie gunks Member

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    thanks all,

    i used a nickel. and then i dove in. i had to weigh out 750g. i did not think it was accurate at that weight so i reweighed it in 200g increments...it came out good.

    i developed my first set of negs last night.....well.....it worked! i guess i was close enough.

    so the phenidone is the most crucial huh? my recipe only called or 2g of phenidone amazing that a small amount will through it all off.

    thanks again.

    eddie
     
  15. rwyoung

    rwyoung Member

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    Those chemicals that will keep well in solution can be measured out into 10% (or higher or lower) solutions. Then when you need only 0.1g of something you can go back to your solution and extract the appropriate volume to contain 0.1g of whatever. Keep in mind that if you do use solutions to manage your small quantities, the total volume of water (or whatever fluid you have selected) in your formula is affected by the addition of your percentage solution.

    In other words, you are adding not only the 0.1g of X but also perhaps 100ml of water so subtract that 100ml of water from what is called for in the recipe.
     
  16. srs5694

    srs5694 Member

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    My understanding is that quantities of phenidone need to be precise in absolute terms simply because the quantities are so small. For instance, if a formula calls for 0.5g of phenidone, an error of 0.1g represents 20% of the target amount, whereas an error of 0.1g in 5g of metol would be just 2% error. As rwyoung suggests, mixing a stock solution can help with this if your scale isn't precise enough. For phenidone, propylene glycol is a good option for a solvent; phenidone reportedly keeps quite well in propylene glycol.
     
  17. gainer

    gainer Subscriber

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    Also, consistency is more important in most photographic processes than absolute accuracy. Two persons may get slightly different results from what is ostensibly the same process. If you were to use different sized pebbles as your standard weights, you couldn't tell others exactly how to duplicate your results, but you could duplicate them for yourself with each new batch.

    The most precise measurement of weight is by substitution. If you want a penny's worth of phenidone, put a penny in a container on the pan and do whatever is necessary with the sliders to balance it. Remove the penny and add phenidone to the same container until balance is restored. Put that penny away for safekeeping and use it every time you need a penny's worth of something (other than thoughts). Now you need have no concern for the accuracy of the weights. You can use your own set of pebbles or other found objects to make a truly personal developer. Nobody can steal your recipe, but you can make it the same every time.

    Anybody who says I'm not a bit "off" is a bit "off".
     
  18. dancqu

    dancqu Member

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    Seven hundred and fifty grams. I'd have used
    a quarter. That many grams of something plus
    two grams of phenidone. Some formula! Dan