I need a decent scales for making my own chemistry. In the past I used one belonging to a friend but I would like one for my own darkroom now. An accuracy of 0.1 would be fine and a capacity of say 200g. Any good suggestions?
Scales for Mixing Chemistry
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In my motorhome darkroom I use a small pocket scale for reloading ammo. It will switch from grains to grams. In the main darkroom I use ohaus beam scales retired from school chemistry labs. I bought them when the schools were changing to more mundane curriculum that didn't make the kids heads hurt so much.
There are also many models on amazon.ca for under $20. On amazon, search for "gram scale .1" or "gram scale .01". I suggest getting one with .01 resolution and a calibration weight. Here's one for $30 with .001 (milligram) resolution:
Uniweigh Milligram Scale
But check your max of 200g will all models.
Uniweigh Milligram Scale
But check your max of 200g will all models.
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Cheap digital scales (as some have mentioned) sound like a minefield to me - caveat emptor territory. I assume you understand the differences between <accuracy, precision, and resolution>?
One of the things I have learned in reloading is repeatability. If I weigh a 180 grain bullet in a scale it needs to be 180 grains every time I put it on the scale. Not 181, 179, 184, 180. Some of the digital scales I have used in the past had that problem. Not the good triple beam scales or the balance beam scales. I use a triple beam scale in the reloading room too that is in grains. Ohaus dialagram is nice too. But and this is to be considered also, if your scale is inconsistent when you mix Kodak d-72 developer you may end up making Dupont 53 D developer instead, and it will still develop paper just fine. When you start mixing phenidone developers you need fine resolution with your scale.
There's a lot of these fool proof balances on Ebay. Go Analog!
And in reality are plenty accurate, precise and consistent unless you're involved in some high-end research or something. For a darkroom user, even a professional ones they work just fine. The only downside is that they don't have the kind of longevity of a triple beam model. I've had several cheap digital Chinese scales, and they all were amply sufficient and perfectly usable for any darkroom work I've done with them.
I have a Sunbeam postal scale under $25. It's very accurate as I checked it with known weights.
I have never weighed chemicals for making darkroom formulas, so I will defer to your greater experience. Every craft and every craftsman must come up with their own definition of what it means to say a measurement is "close enough." If cheap digital Chinese scales are close enough for mixing up darkroom chemistry, then I am delighted to hear about it. We live in marvelous times!
When reading about cheap digital scales on Amazon's website, my main concern was not so much with the scales, but with the lack of education by the users of those scales. I read many comments by users who are convinced the pocket scale they bought for less than $20(USD) is accurate to +/- 0.01g. In many cases, the Amazon description did not include any specification for accuracy. The customers assumed 0.01g accuracy based only on the readout resolution.
And when a specification for accuracy is given - typically +/- 0.03g or 0.05g - it is not clear to me if the manufacturer is claiming that accuracy over the entire measurement range. Most of the $20 scales I looked at come with a single calibration weight - either 50g or 100g. After working in a clinical laboratory for 22 years, I am skeptical of single point calibrations. Even if the response is totally linear (unknown), it still takes 2 points to define a line, right?
It may be that these $20 scales can deliver their advertised accuracy over the entire measurement range - but I would want to prove that by measuring a set of several calibration weights covering the entire range of measurements that I would actually be making. And I would want to check each weight often enough to see what kind of variability to expect.
Again I am not disputing your claim that these scales are good enough for darkroom chemistry. I am only trying to point out that consumers might want do some homework before trying to buy and use one. And I would second the suggestion by @AgX to avoid sellers that do not provide full specifications.
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In Germany we a had a criminal court case were wrong use by the defendant of a digital scale was one issue...
I have a assortment of balances, all mid to late 20th century. Several Ohaus balances that cover ranges from 0.1g to a massive solution balance that will weigh up to 20 kg.
I have a couple late 70's early 80's Sartorius top loading single pan electronic balances, made in Germany. Balances are fun.
I have a couple late 70's early 80's Sartorius top loading single pan electronic balances, made in Germany. Balances are fun.
Good. Because all you said about accuracy claims vs. reality might very well be right, and I agree with it mostly, but practical, hands-on experience suggests it is not a problem.
Can't argue with that!
I am curious, in your experience with making up developers from scratch, what is the smallest amount you have ever needed to weigh? @Doc W mentions wanting 0.1g accuracy, and a maximum capacity of 200g - but what minimum weighing capability is needed?
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In most cases I don't need to go below 500mg, with maybe the odd excursion to 100mg, but that's quite rare. For stuff like phenidone it makes more sense to just mix e.g. a 1% solution in glycol and then measure that using a pipette when making a small batch of developer. The digital scale I use most claims 1mg resolution (50g total range), which I think is ludicrous, but it does offer a resolution safety margin.
If you read for instance the paper that the late Pat Gainer once wrote about teaspoon and tablespoon measurements, it's quite obvious that resolution-fetishism just isn't necessary or even productive when it comes to photo chemistry. The real-world impact of being let's say 5% in error when weighing something is just so small that it's not worth losing any sleep over. Maybe whrn compounding C41 or E6 developers you need a bit more accuracy, but even then, working with stock solutions for things like potassium iodide pretty much solves the whole issue.
Long story short, rest assured that your typical $10 Chinese digital H-bridge scale will be plenty good enough for surviving chemical darkroom adventures.
If you read for instance the paper that the late Pat Gainer once wrote about teaspoon and tablespoon measurements, it's quite obvious that resolution-fetishism just isn't necessary or even productive when it comes to photo chemistry. The real-world impact of being let's say 5% in error when weighing something is just so small that it's not worth losing any sleep over. Maybe whrn compounding C41 or E6 developers you need a bit more accuracy, but even then, working with stock solutions for things like potassium iodide pretty much solves the whole issue.
Long story short, rest assured that your typical $10 Chinese digital H-bridge scale will be plenty good enough for surviving chemical darkroom adventures.
510 Pyro and FX55 developers require 0.375g and 0.1g respectively of Phenidone.
These are the smallest amounts of black and white chemicals that I use.
As koraks mentioned stock solutions are the way to obtain small accurate amounts.
Phenidone in propylene glycol is the method I use to obtain small amounts.
These are the smallest amounts of black and white chemicals that I use.
As koraks mentioned stock solutions are the way to obtain small accurate amounts.
Phenidone in propylene glycol is the method I use to obtain small amounts.
MattKing
Moderator
This is probably the best reason to acquire a more expensive scale - your results won't be substantially different when using it for most photo chemistry, but you will be much less worried
.If it was me - who mostly uses scales to weigh parcels for shipping - who was starting this thread, I would probably have titled it something like "How critically accurate do I need photo-chemistry mixing scales to be, and which ones are the easiest to use and best value"?
I’m certainly not claiming this is better, but I use an old laboratory beam balance. I got used to these at school, and I enjoy using such a simple device that is nevertheless highly effective. My wife got this one for a couple of pounds at a boot sale. Extremely sensitive and repeatable, and plenty precise enough, but accuracy depends on the quality of the weights used, so you need to be careful over that.
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That's been my experience as well. I have two scales by AWS -- American Weigh Scale (made in China, not America) -- a .01 and a .001 resolution scale, and both are fine. In amazon comments, somebody measured the max error of my 0.01 model: he got +-0.04 g. It calibrates to 0 and 100 g, so assuming max error is around 50 g, that's a max percentage-error of about 0.1%, which is more accuracy than we need for photo chemistry.
Mark Overton
Digital scales can only read to half the last digit, no matter how well they perform. I require at least one more decimal place displayed than I measure.
I was trained on 5-place mechanical lab balances, so I have some feel for accuracy, readability, linearity (deviation over range), repeatability (sequential, and multiples of the same), environmental (drafts) and thermal stability. The little one I use most claims 100g at 0.01g readability, so I expect 0.1g. Seems borne out using test weights.
0.1g is 2% of 5g, which is about he smallest powder unit I would be weighing. Most components are within 1%. Which is fine by me - I am not preparing analytical solutions for ppm/ppb measurements.
A Tare function is useful to save correcting for your weighing boat every time
I was trained on 5-place mechanical lab balances, so I have some feel for accuracy, readability, linearity (deviation over range), repeatability (sequential, and multiples of the same), environmental (drafts) and thermal stability. The little one I use most claims 100g at 0.01g readability, so I expect 0.1g. Seems borne out using test weights.
0.1g is 2% of 5g, which is about he smallest powder unit I would be weighing. Most components are within 1%. Which is fine by me - I am not preparing analytical solutions for ppm/ppb measurements.
A Tare function is useful to save correcting for your weighing boat every time
Can't argue with that!
I am curious, in your experience with making up developers from scratch, what is the smallest amount you have ever needed to weigh? @Doc W mentions wanting 0.1g accuracy, and a maximum capacity of 200g - but what minimum weighing capability is needed?
If minimum load is an issue at a scale one always can add a substantial dead-load. One just has t be aware of the issue...
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