Scale for Weighing Chemistry

Discussion in 'Alternative Processes' started by Neil Poulsen, Jan 11, 2006.

  1. Neil Poulsen

    Neil Poulsen Member

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    What's a good scale for measuring out pt/pd and other alternative chemistries? I was sort of thinking of a double-platform scale with a good set of weights. This would help trim costs. But, will it be sufficient?

    I know that a scale like this can only measure weights in quantum increments. But the water or solvent used can be continuously measured in volume, so I should be able to match any concentration that I want.

    What are other scales that people use that are reasonably priced. What level of accuracy do I need? The amounts of chemistry can get pretty small, for example, when measuring amounts of the oxidizer to increase contrast.
     
  2. David A. Goldfarb

    David A. Goldfarb Moderator Staff Member

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    Good deals to be had at www.balances.com.

    I have a Toyo 250 pocket scale, which is fine for my needs. It seems to be designed for jewelers and drug dealers.

    Generally, as the scale capacity increases the precision decreases, so something like mine with a capacity of 250g and a precision of 0.1 gram is good for most developers in moderate quantities and emulsions. If you're mixing your own fixer or really large quantities, then you may want a scale with a capacity of 500g or more. When I occasionally need to measure more than 250g, I just measure in two batches. For small quantities, you can put a slip of paper on the scale to hold the chemical, and for larger quantities a paper or plastic cup works. Most digital scales let you zero the scale to subtract the weight of the paper or cup.
     
  3. Jorge

    Jorge Inactive

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    This is what I use Neil.

    http://tinyurl.com/dvke5

    Cheap, very accurate and it has a very nice big plate so if things spill they are easy to clean up.
     
  4. Kerik

    Kerik Member

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    I use 2 digital scales, depending on how much mass I'm weiging. For small quatities I use one that is 50 gm max with 0.01 gm accuracy. The other is 400 gm max with 0.1 gm accuracy. Take a look at www.balances.com.
     
  5. avandesande

    avandesande Member

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    You don't need a really accurate(analytical) scale for most things. When you need a precise amount you make stock solutions (like your oxidizer example).

    The biggest advantage of using a digital scale is that you don't have to add tare weight to your measure.
    If you are stuck on analog a triple beam balance is fastest and pretty accurate. It will also measure a wide range of weights.

    http://balance.balances.com/scales/438
     
  6. Gerald Koch

    Gerald Koch Member

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    Double pan balances usually have a slider for adding weight up to 1 gram.

    Powder scales are reasonable and will weigh out small amounts but may read in grains only requiring you to convert measurements between the english and metric systems.

    Electronic postal scales weight to 1 gram.

    Check ebay for Ohaus or electronic Mettler balances.
     
  7. JG Motamedi

    JG Motamedi Member

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    I bought a cheap "myweigh" 100g capacity with .01g accuracy from http://www.oldwillknottscales.com. It works well and is quite small, although it can be a bit temperamental. I think it was $75.

    For larger capacities, I have a triple beam Ohaus which I found in a dumpster outside NYU's chemistry department. No idea why they threw it out as it works perfectly. I suppose it because it wasn't digital...
     
  8. Neil Poulsen

    Neil Poulsen Member

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  9. JG Motamedi

    JG Motamedi Member

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    Neil,

    I don't have any experience with the myweigh scales other than the one I own (Durascale 100). I bought mine specifically because it was the smallest and cheapest scale I could find which could measure up to 100g with a decent accuracy.

    I should clarify that the problems I have had with it are pretty minor; mostly just an annoying blinking display. The scale likes and needs fresh batteries, so I have gone through two set of 4 AAAs in the year I have owned it. It also needs to be kept very clean, but of course you should keep a scale clean.

    For what it is worth, Myweigh has a lifetime guarantee on most of their scales. I would probably buy mine again.

    jason
     
  10. pelerin

    pelerin Member

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    I have an Ohaus that must be a first cousin to JG's. Works well, very cheap and needs no batteries. Just saying "triple beam" may gain you cachet in certain circles... this scale was ugly though. It seems to to be about the right capacity for weighing out photo chemistry and you can't lose the weights. If you buy a used balance make sure that it has the complete set of weights and the proper pans. I took one in recently that wouldn't balance out and, after cleaning it off, found that the pans (marked "l" and "r" and indeed differing in weight) were swapped. Works fine now and, being a neat little thing, I left it on the counter to be admired. The first person I showed it to however asked me, "how do you set it in eighths"(dude)? Sigh, metric conversions for dummies anyone...
     
  11. Baxter Bradford

    Baxter Bradford Member

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    Silverprint in UK sell the Salter 1250 diet scale (dearer than this quick search) http://www.rightonscales.com/web/1250.htm they have a max of 250g and accuracy of 0.1g

    I bought one for mixing B+W Pyrocat HD dev and it works very well. You can press the button to zero when adding succcessive chemicals to make your mathematical life easy!
     
  12. battra92

    battra92 Member

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    A little Off Topic but I love the fact that there are "explosion proof" scales. :smile:
     
  13. Paul Sorensen

    Paul Sorensen Subscriber

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    I love the term "intrinsically safe." What is the alternative, scales that are designed to cause bodily harm? :D
     
  14. edz

    edz Member

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    I'd suggest you keep an eye out for mechanical (pre-1980s) lab analytical balances . As digital has pushed the price of used darkroom gear into a black hole, digital balances have pushed (though changes in the demand and qualification of lab workers) them into the dumps. They are, while less convienient than the electronic models, just as acurate, better made and significantly more long term reliable. They probably sold for over $2000 USD 30-40 years ago which is real terms is many times the current price of state-of-the-art analytical balances. They resolve miligrams if not fractional miligrams-- and are more than sufficient for even phenidone or dimezone measurements.

    For less critical measures (and when you need to measure out more than 100g of something) there are some nice mechanical lab top-loaders also available for very little money. A baby scale is probably sufficient for most of these applications but in today's market I can imagine a good used mechanical baby scale would be more expensive and harder to find than a precision lab top-loader..
     
  15. edz

    edz Member

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    These are often mechanical. Electrical/electronic balances can create little charges (like micro-sparks) and these can be quite dangerous in explosive environments where such a "spark" can set off an explosion. This same logic applies to cameras and why fully mechanical cameras (including cine) continue to have their place.
     
  16. Ole

    Ole Moderator Staff Member

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    "Intrinsically Safe" has a very specific meaning, which you would appreciate if you ever had to work in a gas-filled atmosphere. I do once in a while, and IS is good.
     
  17. BrianShaw

    BrianShaw Member

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    I use an older mechanical triple-beam analytic scale. It was cheap at a garage sale. I think the guy that I bought it from was a retired drug dealer. It's really great for weighing chemicals. But I sweat profusely whenever my brother, the narcotics detective, visits because I can't figure out exactly what the odd residue on the scale's base is.
     
  18. Neil Poulsen

    Neil Poulsen Member

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    Linearity Studies

    Thanks for everyones' input. Based on the feedback, I'm leaning towards a couple of MyWeigh scales, one accurate to 0.005 gm with a 100gm capacity for smaller weights and a triple beam for weighing out larger amounts.

    Has anyone ever done a linearity study on these inexpensive scales by weighing sets of items and seeing if their collected weight equals the sum of their individual weights?
     
  19. Michael Mutmansky

    Michael Mutmansky Member

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    Neil,

    I have two scales, one with .1 gram accuracy and a capacity of 400g, and then other with a .01 gram accuracy with a capacity of 30g, if I remember correctly. The first is an electronic scale, and the second is a micro balance.

    I have to say that I sometimes wish I had larger capacity in the larger scale, because when I'm mixing PO or some other solutions in larger quantities, I have to measure some amounts in multiple steps, but that is a minor inconvienance.

    The smaller scale is a pocket sized balance. These are the preferred tool of the corner drug pusher because they are very accurate and easily transported. I almost never use it, except with a few formulas that requre a very small amount of a chemical (like pyrocat hd). Since I knew I wouldn't use it much at all, I couldn't justify getting a nice electronic scale, and these micro balances are very inexpensive as well, which is another reason they are favored by the drug crowd.

    For almost all the pt/pd chemicals (with the possible exception of chlorate for the A+B method of contrast control), a .1g accuracy scale is sufficient in my experience.

    As for calibration, I checked my scale with the calibration mass that came with it, and it was accurate to within .4g in 200g after being used for many years without calibration. I would not be too concerned about accuracy with a decent electronic scale, except in the very low end threshold region, where it may have some difficulty getting a precise, repeatable measurement. That's the best reason to have two scales with two different ranges and accuracy specifications.

    ---Michael
     
  20. Phillip P. Dimor

    Phillip P. Dimor Member

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    I used to own a Mettler P1200 top-loading analytical balance. I could weigh the condensation from my breath, a human hair, etc.

    It was a beautiful piece of equipment and I miss it dearly. It is absolute overkill but a joy to use. I paid about $40 for it on ebay and calibrated it using pocket change (yes I know, but it was good enough for me)
     
  21. Ed Sukach

    Ed Sukach Member

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    "Pocket change" happens to be fairly accurate.

    As a sideline in a previous life, where I was calibrating scales and balances with class "P" weights, I noted that a new United States dime weighs - pretty damn close to - 3 (three) grams; and a new United States nickel was close to 5 (five) grams.

    RCBS - the Reloading Equipment Supplier (rifle and pistol ammunition) carries a Digital Scale --- RCBS "1500" or something like that ... that looks promising - something like 1500 grains capacity ( I'm too "burned" at the moment to convert anything) and 0.1 grains accuracy - switchable to metric, grams. I am NOT familiar with it - at all - but other reloaders have recommended it. I've got to find time to visit a RCBS dealer and check it out. A Google search for "RCBS" should provide more information.

    If anyone thinks that photographers are overly fussy and "anal" about what they are doing, they should contemplate those who reload their own ammunition - especially the "Bench Rest" group.... UNBELIEVABLY picky and fussy. Makes the fussiest photographer look like a troglodyte.
     
  22. MattKing

    MattKing Subscriber

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    Ed, maybe thats because we relatively rarely have to deal with chemistry that is supposed to explode! :tongue:
     
  23. Ed Sukach

    Ed Sukach Member

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    "Explosion" is not the issue. Powders - both smokeless ("progressive" is a better description) and "black", are safe with a small amount of mandatory care - primers are more sensitive - but nothing to "jump out your skin" over.

    Uniformity IS paramount. Without it, accuracy goes down the toilet - and that is the name of the game in "Bench Rest" shooting.
     
  24. Donald Qualls

    Donald Qualls Member

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    Relative to reloading, though, I have a reloading scale (which I've been using to weigh photographic chemicals recently) that goes to 500+ grains in 0.1 grain increments (15.4 grains to the gram, BTW; that makes the increments about 6.5 mg), with no batteries and very few parts. It's accurate enough that I can see variations much smaller than the 0.1 grain minimum setting increment, and it is in fact possible to set the scale to smaller increments by estimation (the small increment adjustment is on a screw thread, so continuously variable).

    I've had the scale for about 25 years, it's been through something like a dozen moves, and it still swings smoothly, zeroes out easily, and damps consistently. Dunno what I'll do for photo chems if I ever get back to reloading...
     
  25. eli griggs

    eli griggs Member

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    Rcbs scale

    I have the RCBS 5-0-5 and it is a very good scale. It gives a 1/10 of a grain accuracy and worth every cent of the $55-$65 a new one will cost.

    An excellent online source is midwayusa.com. They also carry other good scales, both analog and digital, but the RCBS is pretty much the standard for this type tool.

    If you know a gun collector with a Curio & Relic FFL or someone wiht a dealers license, ask them to order it for you, as MidwayUSA will give a dealer discount if they have their license on file.

    I recommend that you try the Lee powder dipper sets just for a nice set of small plastic dippers. They are calibrated for volume-metric ammo reloading and there is a slide rule for smokeless powders you won’t need, but for darkroom work they are cheap little tools that will come in hand when pulling out chemicals from a jar or package.

    A word of warning if you use any scale that incorporate magnetic damping, like these small scales. If you use florescent lighting, florescent lights can affect the scales' reading if they are too close to the tool. See general rule 11 here www.speer-bullets.com/default.asp?s1=5&s2=19

    Cheers