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  1. #21
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    It wouldn't have been hard for Rube Goldberg to design an automatic system to weight out X grams to the nearest .1 gram. I think I could do it. Think of a see-saw with a fixed weight on one side of a pivot that is bistable. If the pivot is below the center of gravity when the system is in balance, the slightest additional weight will tip the whole thing. It then dumps whatever was poured onto the other side and the fixed weight returns the balance to a stop. You should be able to imagine the rest.
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  2. #22
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    Besides, even if Kodak could guarantee uniformity of what is in the cement mixer, there still is the problem of measuring out 545 grams into each 5 liter package as it went by on the conveyor. There are other ways than my R. G. to measure large and small amounts of liquids and powders into containers on a conveyor. Tell me. It has been a long time since I mixed any Kodak or Ilford developers from powders. Is there not an admonition on the package to use the entire contents?
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  3. #23

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    Quote Originally Posted by gainer View Post
    Is there not an admonition on the package to use the entire contents?
    CYA or more appropriately, CKA.

  4. #24

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    Quote Originally Posted by srs5694 View Post
    Why not? That's how they make lots of things -- a conveyor belt rolls along and, at various points along the way, things are added or something is done to the product. All they'd need to do is put an unsealed bag on a conveyor, dump in 8g of metol at one station, 40g of hydroquinone at the next, and so on, then seal it up. This isn't conceptually any different from how they make other products, ranging from Twinkies to automobiles.
    Wow, let's make an easy thing really complicated and subject to many more possible errors.

    Dump it all into a mixer, mix, apportion by volume. Simple.

    I've never noticed the different chemicals in packaged developers, or lumps, or strata.

  5. #25
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    Quote Originally Posted by Paul Verizzo View Post
    Wow, let's make an easy thing really complicated and subject to many more possible errors.

    Dump it all into a mixer, mix, apportion by volume. Simple.

    I've never noticed the different chemicals in packaged developers, or lumps, or strata.
    You could ask someone at Kodak how they do it. It shouldn't be proprietary information. I'll bet the only time they do it your way is with liquid developers like HC110. Mixing dry ingredients in large quantities is probably more expensive and more likely to damage the ingredients by frictional heating, as well as being more likely to result in inconsistent product quality. But suppose that you have periodic tests of samples from the packaging line and you find a defective sample. The contents of your cement mixer must be assumed defective after the last good sample. The first half of your cement mixer's contents may have contained 90% of the Metol without showing any defective samples. Now you have a problem. Do you add more Metol, or throw away the rest of the mix? The major cost of D-76 is in the sulfite. More than that, the ability to determine that the problem is in the Metol depends on a quantitative analysis. You will be stopping production as well as increasing the cost of production more by testing than any other part.

    Let us not forget that you had to weigh out the ingredients you put into the blender. A chef with the same type of problem would use volumetric measurements of each ingredient that gos into the blender.

    Enough.
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  6. #26

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    Quote Originally Posted by Paul Verizzo View Post
    Wow, let's make an easy thing really complicated and subject to many more possible errors.

    Dump it all into a mixer, mix, apportion by volume. Simple.
    You've still got to get the initial quantities right, and as Gainer points out, when you do it as you're suggesting, you're relying on factors that are hard to measure to get the proportions right, which makes QC more difficult. At least with each machine measuring precise quantities, it's easy to do QC checks along the way -- program the assembly line to dump only metol in the package once every 1,000 packages, then only hydroquinone in the next one, and so on, and pull those packages to check that they've got the right amounts.

    Besides, as I say, lots of things are made in precisely this way. It may be more important that the ratio of, say, metol to hydroquinone is right in D-76 than it is that the ratio of filling to cake is right in a Twinkie, but this sort of manufacturing is a precise science. Check out some TV shows like "How It's Made" or "Modern Marvels" and you'll see examples.

    I've never noticed the different chemicals in packaged developers, or lumps, or strata.
    Presumably they either get mixed up in ordinary normal handling as the bags are sealed up, put in boxes, and shipped; or some station exists to deliberately mix the contents up.

    Of course, we're both just speculating here. I for one am not trying to present a case that this is definitely how it's done; I'm just trying to present an alternative to your proposal, since you said you "...can not believe that the little 1 gallon packet of dry chemicals didn't come from some huge cement mixer...." Perhaps you still won't believe it, but IMHO, it's a perfectly plausible idea.

  7. #27

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    Quote Originally Posted by gainer View Post
    You could ask someone at Kodak how they do it. It shouldn't be proprietary information. I'll bet the only time they do it your way is with liquid developers like HC110. Mixing dry ingredients in large quantities is probably more expensive and more likely to damage the ingredients by frictional heating, as well as being more likely to result in inconsistent product quality. But suppose that you have periodic tests of samples from the packaging line and you find a defective sample. The contents of your cement mixer must be assumed defective after the last good sample. The first half of your cement mixer's contents may have contained 90% of the Metol without showing any defective samples. Now you have a problem. Do you add more Metol, or throw away the rest of the mix? The major cost of D-76 is in the sulfite. More than that, the ability to determine that the problem is in the Metol depends on a quantitative analysis. You will be stopping production as well as increasing the cost of production more by testing than any other part.

    Let us not forget that you had to weigh out the ingredients you put into the blender. A chef with the same type of problem would use volumetric measurements of each ingredient that gos into the blender.

    Enough.
    20 pounds of Metol, 50 pounds of hydroquinone, 100 pounds of sodium sulfite, 20 pounds of borax (IIRC). Mix for ???? hours.

    It's done all of the time with dry cement mixing. As long as the ingredients are in the mixer long enough, it will be a uniform mixture.

    I was hoping PE could "weigh" in on this.

  8. #28
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    Maybe it would be OK if you were going to make glue out of the ingredients, but I just cannot imagine Kodak trusting that each of the 5000 or so liter packs of D-76 would be the same. If one is off, at least one other is also off. In such a production line, you try to avoid depending on probabilities. You would like the probable error of measurement of each ingredient to be less than 1/3 the tolerable error in that ingredient.

    If Kodak did it your way, how would the contents of the mixer be transferred equally into ~1000 5 liter packages? Would a worker with a scoop and a scale or balance do it manually? Would someone design an automatic weigher-loader device to do the package filling on an assembly line? If such a contraption can be designed, why not use 4 of them to put each of the ingredients into packages as they move along the line, thus eliminating the expense of a huge mixer and the uncertainty of its output?
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  9. #29

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    Quote Originally Posted by gainer View Post
    Maybe it would be OK if you were going to make glue out of the ingredients, but I just cannot imagine Kodak trusting that each of the 5000 or so liter packs of D-76 would be the same. If one is off, at least one other is also off. In such a production line, you try to avoid depending on probabilities. You would like the probable error of measurement of each ingredient to be less than 1/3 the tolerable error in that ingredient.

    If Kodak did it your way, how would the contents of the mixer be transferred equally into ~1000 5 liter packages? Would a worker with a scoop and a scale or balance do it manually? Would someone design an automatic weigher-loader device to do the package filling on an assembly line? If such a contraption can be designed, why not use 4 of them to put each of the ingredients into packages as they move along the line, thus eliminating the expense of a huge mixer and the uncertainty of its output?
    I seldom have a chance to argue with a rocket scientist! So you mix and mix until uniform. The amount of variability between a scoop of the batch here and one there will be difficult to ascertain. The concrete made from a cement mixer is uniform.

    So, with some simple calculations of weight and volume, you get your amount to put into that one gallon foil packet. In production, it's easy to measure volume and then drop it into something with a sliding measure. Position A, load. Position B, drop.

    I would far more trust a scenario I envision than measuring four separate ingredients down to the 8 gram level, rapidly, no less. That's four times the possible error of one "scoop" measurement.

    Where's PE?

  10. #30

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    Have you ever put a bag of dry cement in a cement mixer? When you put it in there and turn it on all the lighter powders go to the bottom and the rocks float up to the top what you end up doing is giving the perfect situation for the powders to go to their natural position by density.

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