Measuring chemicals in powder form - how?

B-3 · Nov 24, 2005

For those of you who use chemicals that come in powder form - what do you use to make your measurements? The stuff comes in relatively large amounts, but you only need a little at a time... Do you have scales? If so, where did you get them? Is it the kind of thing you get at the local pharmacy? Any recommendations? Thanks.

Gay Larson · Nov 24, 2005

I recently bought chemicals for bromoil prints and I went to Walmart and bought a food scale that had metric measurements along with ounces. It cost about $17. It is stainless steel. I haven't used it yet but I am sure it will work just fine.

Kevin Caulfield · Nov 24, 2005

I don't do it myself, but there are a few places, some online, who sell nifty little electronic balances, which are ideal for weighing very small amounts. I'm sure somebody will point you to such a place.

Jeremy · Nov 24, 2005

I ended up getting an old laboratory digital scale on eBay for really cheap. Very high quality lab equipment can be bought cheap on the net nowadays.

Sinarfar · Nov 24, 2005

tripple beam scale, tag sale, $3.00, nice find.

ann · Nov 24, 2005

at this time i use an electronic scale, in the past a triple beam scale.

You can also use measuring spoons as found in the kitchen . In the Ancell book he breaks down amounts into using everyday measuring spoons.

Photo Engineer · Nov 24, 2005

ann said:
at this time i use an electronic scale, in the past a triple beam scale.

You can also use measuring spoons as found in the kitchen . In the Ancell book he breaks down amounts into using everyday measuring spoons.

I have tried measuring powders by both volume and weight.

Using different samples and cross comparing, I have found that there can be up to a 20% error in measuring different crystal forms by volume, but there is no error by weight. For example, a crystalline KBr that I have differs in volume by 20% compared to a powder sample of the same chemical. In other words 10 ml of the crystals equals 8 ml of the powder for the same weight of KBr.

If you wanted 10 grams, you would actually have 8 grams if you measured out the suggested volume. By extrapolation, you might have 80 grams of something you wanted 100 grams of if you used volumetric measure from two samples.

If you feel that you can tolerate this, then use whatever seems to work for you in the darkroom.

PE

David A. Goldfarb · Nov 24, 2005

www.balances.com

Get a scale that measures in tenths of a gram. To mix your own developers a capacity of 250 g is sufficient, but if you want to mix your own fixer, you might want more capacity--500 g or more, but not so much that the scale won't give you the precision you need for small quantities.

I use a Toyo 250 pocket scale.

mgb74 · Nov 24, 2005

Scales for reloading pistol and rifle cartridges are effective and accurate. Only drawback is that your will need to convert from grains to grams.

srs5694 · Nov 24, 2005

I may be wrong, but I get the impression that Bruce is talking about bags of powdered commercial developer, such as Kodak XTOL or Ilford ID-11, not about mixing developers (or whatever) from scratch. If I'm right about this, the general advice is to mix up the whole package at once and store it in tightly sealed bottles (ideally glass bottles). The problem with trying to mix up part of a package of powdered chemicals is that the different particles in the package have different sizes, weights, and so on. The result is that if you scoop out a given amount, either by weight or by volume, you probably won't get the same proportion of chemicals from one session to another. You can minimize this problem by mixing well before measuring, but there's still likely to be some slop. Most commercial powdered chemicals are designed to last several months once mixed, assuming reasonable storage conditions, so you shouldn't have problems with the mixed solutions going bad unless you buy in quantities that are far too large for your needs.

Bob F. · Nov 25, 2005

For DIY developers, toners etc, I use two electronic scales: one a normal kitchen type for large amounts and another scale reading down to 0.01g (max 100g) for small quantities.

ID-11 etc I mix up in one go from the packets as recommended.

Cheers, Bob.

Mike Kennedy · Nov 25, 2005

I think srs5694 nailed the answer.
When I told my darkroom instructor how I was saving $$ by mixing small amounts of powered D76,Fix etc. she commented that these formulas had many components of different weights. Ergo,each small batch I mixed up was different from the last. (man oh man do those old negs.of mine SHOW that difference).
Personally,I stick with liquid or small packets. Always fresh,always consistent.

Mike

B-3 · Nov 25, 2005

Good info - thank you, all of you, very much.

Just to clarify: I WAS thinking about those bags of commercially available developers and imagining that one takes a bit out, mixes the amount needed, then stores the rest in its dry state. I see now that is NOT the way to do it.

The long version (in case you're interested): I just recently constructed my own darkroom and then signed up for a darkroom class which was canceled for lack of interest. So I'm reading books, papers, websites, fishing through the threads here, trying not to ask any completely imbecilic questions. (Yeah, I know, too late for that.) I think I'm all outfitted, just need paper and chemicals. I'll go one step at a time and start with enlargements (I have many sheets of negatives that I had commercially developed). The local photo store carries chemicals (Dektol, for example) in powder form and Ilford stuff in liquid form. Liquid seems easier so I buy that. Then I'm also thinking I want to try contact prints at some point and so I read up on Azo - turns out I need Amidol (among other things) and this appears to be available only in powder form, so I figure I might as well just get whatever I need and not be put off by the powders. A little more equipment, maybe - but why stop now?

If you've read this far, maybe you can tell me where one gets things like sodium sulfite, potassium bromide, BB compound? How do I ensure that I'm getting the proper ratios of sodium thiosulfite and sodium bisulfite? Am I making this too complicated on myself?

Bob F. · Nov 25, 2005

Liquid is convenient, but you pay for it - shipping all that water around the world costs money...

Look at the Photographer's Formulary (http://www.photoformulary.com/DesktopDefault.aspx) who are APUG sponsors. More chemicals than you can shake a bunsen burner at. They do some pre-packed powdered chemicals such as Amidol based developer IIRC.

Cheers, Bob.

John Bartley · Nov 25, 2005

Bruce said:
...
If you've read this far, maybe you can tell me where one gets things like sodium sulfite, potassium bromide, BB compound?

Not sure where Paradise is, but in Canada, you can use Dead Link Removed . They've given me very good service on the little bit I've bought.

cheers

srs5694 · Nov 25, 2005

Bruce said:
Then I'm also thinking I want to try contact prints at some point and so I read up on Azo - turns out I need Amidol (among other things) and this appears to be available only in powder form, so I figure I might as well just get whatever I need and not be put off by the powders.

You don't need Azo or amidol developers to do contact printing. If you just want to make contact sheets of 35mm or MF negatives, you'll probably do just fine with your regular enlarging paper and developer. I'm not positive, since I'm not into this myself, but I believe that those who go all mushy over Azo mostly use large format negatives. Even with such negatives, it's possible to do contact prints using non-Azo papers and non-amidol developers. I'll leave it to those who know more about Azo and amidol developers to expound upon their benefits, if they choose to do so.

Bruce said:
If you've read this far, maybe you can tell me where one gets things like sodium sulfite, potassium bromide, BB compound?

I'm not sure what you mean by "BB compound," but raw chemicals can be bought from several sources, including Photographer's Formulary, Digital Truth, Art Craft, The Chemistry Store, and Dead Link Removed (Most of these are in the US, but JD Photochem is Canadian. If you live on another continent, other suppliers would probably be better.) Some items (ascorbic acid, sodium carbonate, etc.) can be bought in a local supermarket if you know which boxes to buy. Read on, though....

How do I ensure that I'm getting the proper ratios of sodium thiosulfite and sodium bisulfite? Am I making this too complicated on myself?

If you're just starting out, I'd recommend against buying bulk chemicals (metol, sodium sulfite, etc.) and mixing your own developers. This is a skill that takes learning, and you'll be learning enough without dealing with mixing raw chemicals. Just buy your Dektol (or whatever) from your local photo dealer or from a mail-order outfit like B&H or Freestyle and don't worry about the proportions of various components. If you want to get into "darkroom Mad Science," then you can do so later, once you've learned the basics of using the pre-measured (liquid or dry) stuff from a manufacturer. Starting out with this approach just makes the learning curve steeper and introduces variables that are best kept out of the picture.

B-3 · Nov 25, 2005

Thank you for that! A lot of thought and effort went into your message. I think I do have everything I need for making basic enlargements and I'm ready to give it a try. I have gotten myself confused sometimes when, say, the basic manual seems straightforward but other sources add layers of complexity. Part of it is my desire to be ready for the next step before I even know what it is - possibly a byproduct of considering such dilemmas as - an 8x10 easel would probably suffice, but what if I later decide I want to make 11x14s? I'm trying to anticipate when I should probably stop where I am and just do the deed.

I admit to having little knowledge about them, but also to being intrigued by the idea of contact prints as finished products (rather than proof sheets). I realize this means larger negatives and that the best way to get large negatives is to use a large format camera. OTOH, I get the idea that there are other ways to get a large negative - there are digital means, but I think there are also "traditional" enlarged negatives. Personally, I'm thinking I'd like to try building combinations of multiple, smaller images - kind of like contact sheets, but with each image being purposefully selected on a thematic or graphic basis. But that's way down the road. I guess there's no reason I couldn't do this with "standard" enlarging paper and the appropriate developer before I plunge into new combinations.

Thank you again, so much. You've been a big help (and this has helped to clarify my thinking too).

All the best,

Bruce

P.S. "BB Compound" is something I saw in a recipe in an essay in an old View Camera magazine. I think it has "anti-fog" properties and since I had no idea I was supposed to take anti-fog steps this sent me back to more researching and head-scratching and wondering if I had everything I needed.

David A. Goldfarb · Nov 25, 2005

BB compound was something Weston used. It seems to have been some sort of commercial preparation of benzotriazole, maybe combined with something else in the way that Edwal Liquid Orthazite is a 3% solution of benzotriazole with sodium sulfite. My guess is that "BB"=benzotriazole+bromide.

bcjesq · Nov 26, 2005

Like the other respondents, I use an electronic pocket balance. Mine's a Tangent 102, which is a 100g battery powered scale. You can get one online for around $45 (http://www.itinscales.com) , and there are lots of other good pocket balances in that price range. The good scales over 100g get expensive fast, so I just use a styrofoam cup and weigh in batches up to 100g until I reach the required amount.

Good luck.

Wayne · Nov 26, 2005

Photo Engineer said:
If you feel that you can tolerate this, then use whatever seems to work for you in the darkroom.

PE

I dont see this as a problem, I always get the same forms of a given chemical (doesnt everyone, given the choice?), of course you have to recalibrate your teaspoons if you decide or are forced by circumstance to switch forms.

Photo Engineer · Nov 26, 2005

Wayne said:
I dont see this as a problem, I always get the same forms of a given chemical (doesnt everyone, given the choice?), of course you have to recalibrate your teaspoons if you decide or are forced by circumstance to switch forms.

Wayne, that is the problem. I have two batches of KBr that differ 20% in volume vs weight measurement. They were bought from two reputable dealers.

Both bottles are crystalline, analytical grade. The crystal size is all that differs between these two. Therefore, their packing density differs. You will also see this in one bottle of chemical as the powder will settle towards the bottom and the larger crystals will migrate to the surface (like frost heaving rocks). Therefore, you can actually get a variation in crystal density from the top to the bottom of a single bottle of chemical if the material is nonuniform.

Same variation I see in the KBr is true, I suspect, of several other chemicals I use, but since I use weight for measurement, I have not investigated them. The KBr pair is the only one I tested.

I'm saying to you, use what works. I'm also passing along the experience gained from my long years of benchwork as a professional chemist and engineer.

I'm getting tired of this question actually.

If an engineer told you that a bridge looked unsafe, and you said "well, I went over it yesterday" and the engineer says "I just inspeced it". Well, you get what you deserve if you go over the bridge. He may or may not be right, but he gave you the best advice he knew based on his background and education and training.

That is all I can do. Many refute my statements on this subject. I have run the tests to my satisfaction and will not use volumetric measurement of solids for any photographic or other chemical purpose.

PE

Wayne · Nov 26, 2005

Photo Engineer said:
Wayne, that is the problem. I have two batches of KBr that differ 20% in volume vs weight measurement. They were bought from two reputable dealers.

Both bottles are crystalline, analytical grade. The crystal size is all that differs between these two. Therefore, their packing density differs. You will also see this in one bottle of chemical as the powder will settle towards the bottom and the larger crystals will migrate to the surface (like frost heaving rocks). Therefore, you can actually get a variation in crystal density from the top to the bottom of a single bottle of chemical if the material is nonuniform.

Same variation I see in the KBr is true, I suspect, of several other chemicals I use, but since I use weight for measurement, I have not investigated them. The KBr pair is the only one I tested.

I'm saying to you, use what works. I'm also passing along the experience gained from my long years of benchwork as a professional chemist and engineer.

I'm getting tired of this question actually.

If an engineer told you that a bridge looked unsafe, and you said "well, I went over it yesterday" and the engineer says "I just inspeced it". Well, you get what you deserve if you go over the bridge. He may or may not be right, but he gave you the best advice he knew based on his background and education and training.

That is all I can do. Many refute my statements on this subject. I have run the tests to my satisfaction and will not use volumetric measurement of solids for any photographic or other chemical purpose.

PE

I misunderstood you, I thought they were 2 obviously different forms when you said one was crystal and one powder. I have used teaspoon measures with good success in the past, but since I got a triple beam for $5 I'm a weight man now.

Photo Engineer · Nov 26, 2005

Wayne, I may have said that actually. If I did, sorry.

They are both crystalline, but one is rather coarse and the other is like a fine powder. Looking at them closely, they are both the typical KBr cubes, but just radically different in size. That is why I used them for this test initally, as it made me suspect that there would be a big difference and that in formulas that relied on the antifoggant capabilities of KBr, this could present a problem.

PE

srs5694 · Nov 26, 2005

Bruce said:
Part of it is my desire to be ready for the next step before I even know what it is - possibly a byproduct of considering such dilemmas as - an 8x10 easel would probably suffice, but what if I later decide I want to make 11x14s? I'm trying to anticipate when I should probably stop where I am and just do the deed.

Well, you've got to stop speculating and preparing somewhere and just start doing it! (At least, if you want to do it at all.) As to easels, my view is that they're so cheap used on eBay that you might as well just start out with something that looks OK and if you decide you need something more or better, upgrade later. I've got about half a dozen eaself of different sizes and designs. I'll probably put at least one up on eBay myself before too long.

"BB Compound" is something I saw in a recipe in an essay in an old View Camera magazine. I think it has "anti-fog" properties and since I had no idea I was supposed to take anti-fog steps this sent me back to more researching and head-scratching and wondering if I had everything I needed.

The only anti-fogging step you must take is to ensure that your darkroom light levels are sufficiently low. (This includes light leaks, safelight levels, and control of stray light sources, like cordless phones that might light up when a call comes in.) As I understand it, anti-fog compounds in developers are mainly used to control age-related fogging in paper that's old or that's been improperly stored. It's not something you'd normally need to be concerned with when just starting out, unless maybe you've inherited a bunch of "mystery paper." In that case, you might want to buy a box or two of more recent stuff to begin with. That'll reduce the odds of your getting bad results and having to consider the possibility that it's the paper.

Wayne · Nov 27, 2005

Photo Engineer said:
Wayne, I may have said that actually. If I did, sorry.

They are both crystalline, but one is rather coarse and the other is like a fine powder. Looking at them closely, they are both the typical KBr cubes, but just radically different in size. That is why I used them for this test initally, as it made me suspect that there would be a big difference and that in formulas that relied on the antifoggant capabilities of KBr, this could present a problem.

PE

I agree. Now there are some cases where i will probably still measure by volume even though I have a scale, but for developers I will use the scale from now on. When making a citric acid stop for example, or a plain hypo/sulfite fix, the exact amounts are not that critical (in my non-chemist understanding, feel free to correct me). I usually just dump a short teaspoon of citric acid into a liter or so of water, and IIRC ( I havent done it in a few years) I used to use roughly 25% hypo to water by volume for a plain non-hardening fix.

Measuring chemicals in powder form - how?

B-3

Gay Larson

Kevin Caulfield

Jeremy

Sinarfar

ann

Photo Engineer

David A. Goldfarb

Moderator

mgb74

srs5694

Bob F.

Mike Kennedy

B-3

Bob F.

John Bartley

srs5694

B-3

David A. Goldfarb

Moderator

bcjesq

Wayne

Photo Engineer

Wayne

Photo Engineer

srs5694

Wayne

Measuring chemicals in powder form - how?

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