weigh the volumes

[Rick A]

"YMMV" The heart of the matter.

 

[Maris]

I have a background in quantitative analytical chemistry and know well the difficulty of weighing out precise quantities of solids and liquids.

Solids vary in their friability, stickiness, bulk density, moisture content, purity, activity...and specific gravity. Dispensing powders often requires the use of a vibrating spatula to deliver minute grains to approach a target value. If the target is exceeded then powder is removed and the approach is tried again. Liquids vary in viscosity, volatility, and surface tension so plus or minus one drop can vary widely. Good weighing practice dictates that substance weighing should not be done above a precision balance (contamination!) but rather on the bench beside it. It can take many tries and many minutes to get very close to a target weight. A mistake in over-dispensing liquid onto powder is hard to correct especially if you've used all the powder and kept none in reserve.

Owners of fine analytical balances can confirm that the indicated mass of most powders and liquids never actually settles. There is always water evaporation, absorption, oxidation, etc, going on and the numbers in the last decimal place keep rolling.

Because of the difficulty of the gravimetric approach to mixtures the commonest standard in chemistry for reagent concentrations is w/v, that is weight on volume. The implication is that you will weigh out the solid (gravimetric) and then place it in a vessel of known volume and then add liquid (volumetric) to achieve a final target volume of solution (not solvent).

Most photo processing involves "bucket" chemistry and any consistent, convenient approach is good enough. There are plenty of other variables to control without overly fussin' in the darkroom.

 

[schyter]

many thanks Maris,

I have a little difficulty with the translation into Italian, but of course it's my fault.
I understood the meaning of your reasoning.


I want to emphasize one thing that I realize only now for not explaining well ... "" weigh the volumes "" I refer only to liquids developers !!! excuse me

 

[edcculus]

I like your method! As someone who does a lot of baking, this makes a lot of sense to me. I NEVER measure baking ingredients by volume, always by weight. In baking measuring dry ingredients by volume will typically result in errors, and is not very repeatable. Its also very easy to scale batches of bread using weight.

If you limit yourself to a small amount of different chemistrys, you only have to do the calculations once anyways. Write the weights down and paste them to the wall in your darkroom. Currently, all of my darkroom chemicals are liquid (HC-110, ilford rapid fixer, Ilford paper developer etc). So in my case volumes are pretty easy, except your method would only dirty one beaker.

 

[BrianShaw]

I like your method! As someone who does a lot of baking, this makes a lot of sense to me. I NEVER measure baking ingredients by volume, always by weight. In baking measuring dry ingredients by volume will typically result in errors, and is not very repeatable. Its also very easy to scale batches of bread using weight.
...

For me the errors aren't the issue/concern but convenience and scalability. Bowl, tare, flour, tare, yeast, tare, sugar, tare, fat, tare, water... mix knead and rise.

 

[Maris]

many thanks Maris,

I have a little difficulty with the translation into Italian, but of course it's my fault.
I understood the meaning of your reasoning.


I want to emphasize one thing that I realize only now for not explaining well ... "" weigh the volumes "" I refer only to liquids developers !!! excuse me

Weighing the volumes is ok if your required accuracy is +/- 200mg which can be done reasonably well on a balance that indicates +/-100mg. The smallest drop of water is nominally 50mg which is well within the margin of error. Rodinal is "watery" and I expect its minimum drop size to be similar. A viscous developer like HC110 doesn't form consistent drops and dispensing it is best done with a displacement pipette alias syringe. This is more troublesome but accurate enough if done slowly and carefully.

 

[schyter]

Weighing the volumes is ok if your required accuracy is +/- 200mg which can be done reasonably well on a balance that indicates +/-100mg. The smallest drop of water is nominally 50mg which is well within the margin of error. Rodinal is "watery" and I expect its minimum drop size to be similar. A viscous developer like HC110 doesn't form consistent drops and dispensing it is best done with a displacement pipette alias syringe. This is more troublesome but accurate enough if done slowly and carefully.

thank you very much for the intervention and not just because it supports my methodology ...
I thank all the friends who discuss here, without assume absolute truths.
The important thing is to photograph... the method is just a tool.

 

[MattKing]

If you use this measure by weight approach, you may have trouble finding others who can understand your approach. So it may reduce the numbers of people who you can look to for advice and assistance.

 

[Silverprint Italy]

Mr Schyter!
So at the end you got the same replies all over the world.

As everybody everywhere told you (did you forget to post your theory somewhere?), your (adjusted from previous version) method, though correct, is generally unpractical.
The original Schyter method (as proposed in the italian forums) assumed every liquid photo chemicals to weight as much as water. I took some weeks and a lot of effort to have Mr Schyter accept that the specific weight had some relevance.

God bless the new expert!

 

[rcmartins]

Not sure if anyone has stated what I am going to state before, and apologies if someone has.
The method the OP proposes is OK but needs to be better explained. The physical quantity that relates mass to volume is the volumetric mass density. For those who don't know specific gravity is the ratio of this quantity for the substance at hand to the volumetric mass density of water (it can be other substance, but water is usually the reference people use). The thing is, mass density changes with temperature and pressure. While pressure is usually not a problem, temperature is. The change is higher than you might expect and definitely much higher than oxidation or evaporation (unless boiling). To keep accuracy throughout the year one must determine the specific gravity of every liquid used in the developer formulation for the altitude and temperature at which the preparation takes place. This should also be done always with the same water since water varies a lot in their mineral composition and thus its volumetric mass density also changes.
Another difficulty that can arise is that the volume at stake might imply large weights that render the resolution of weight scales coarse. Yet another problem is with multi-part developers like Pyrocat for which part A has a much different specific gravity than part B. The difficulty here is that it makes the relation between parts much different than what is stated for volumetric ratios and worst, varies between the different formulations of part A. For a newbie this can be a true nightmare.
This said, if one has the habit of doing these preparations using the same liquids at the same temperature at the same place, everything should go fine. I do this all the time, but not for convenience. I do it for accuracy, but is a painstaking and labor intensive accuracy that I only delve into if absolutely required.
raul
PS: I am a bit, ok way past my bedtime. Hope coeherence and clarity haven't gone to rest before me

 

[schyter]

Mr Schyter!
So at the end you got the same replies all over the world.

As everybody everywhere told you (did you forget to post your theory somewhere?), your (adjusted from previous version) method, though correct, is generally unpractical.
The original Schyter method (as proposed in the italian forums) assumed every liquid photo chemicals to weight as much as water. I took some weeks and a lot of effort to have Mr Schyter accept that the specific weight had some relevance.

God bless the new expert!

I do not want to be argumentative with you, because even if the language is not an opinion, I received positive feedback in this forum.
In addition to high rates of good education here in APUG. More swinging (good education) in the Italian forum.

 

[Claudia Moroni]

[...]
Things become even more important when you are using multiple solutions (A+B+C)... How many cylinders, jugs, and syringes avoid washing?

[...]

because this system has created a cruel irony and derision ???
I've made mistakes ???

Many thanks at all !! Luigi ;/)

I've been following this discussion since it started in the Italian forum.

Personally I believe this system isn't really practical and I wouldn't recommend it to a beginner.
I think someone who's starting out and doing his/her first development would probably be more daunted by the weighting and math involved in Luigi's method than in the prospect of rinsing out a few cylinders.

I also have a doubt about the procedure for divided developers since you claim that, especially in this case, your method is superior because, among other things, it saves on washing up several graduated cylinders.
My doubt is: in this case don't you have to rinse the plastic bottle that you use to weight the chemicals anyway therefore invalidating the washing up argument?

I'm glad this system is working for you, but I think you've been mocked because of your insistence on getting everyone to agree with you and the way you changed your claims mid-conversation (you started the discussion by saying that every developer density was the same as water and you corrected your procedure once someone pointed out that their mass density isn't always the same).

Overall I have a strong feeling that the cause of the mockery isn't only the fact that you're trying to convert people to your method, but the way you go about it.
If your method works for you, keep using it, but I don't see the point in pretending to be right at every cost.

 

[schyter]

I do not want to sound arrogant and I can respond point by point to the conclusions of Claudia. I understand that I have grown weary the reader. Then, if the thing interesting to Claudia or other users still post my thoughts. Otherwise I'll stop here.

 

[MartinP]

The weighing method does not save on cost of equipment, durability of the tools, simplicity or time taken, nor does it improve repeatability. However, it may be useful when finding oneself on a deserted island with an expensive precision scale, a pile of clean jam-jars, some chemicals and a load of film to develop.

 

[schyter]

The weighing method does not save on cost of equipment, durability of the tools, simplicity or time taken, nor does it improve repeatability. However, it may be useful when finding oneself on a deserted island with an expensive precision scale, a pile of clean jam-jars, some chemicals and a load of film to develop.

thanks MartinP for your considerations. If you can itemize better the four points you have mentioned so we can compare with my.


cost equipment > 6,79€ precision balance (0,1gr / 1000gr) http://www.ebay.it/itm/390630329948?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

durability > consider similar (breaks the scale / breaks the glass cylinder)

time taken > lower with the weighing or same

precision and repeatibility > and again without a doubt the weighing. In a dilution hypothesized (23.6 ml) of developer, will be forced to round the value (24ml?)
the next time you're sure to repeat exactly 24ml? yes,with the method of weighing.

 

[Rick A]

Ok--we give up-you are right and the rest of us are wrong.

This thread is all about Proverbs 18:22

 

[schyter]

Ok--we give up-you are right and the rest of us are wrong.

I suspected this from the beginning !! many thanks... eh eh eh

 

[Vaughn]

After years of carbon printing -- carefully weighing out 90 grams of gelatin and 60 grams of sugar every time I make a batch of "glop", I think I will just see what volumes those amounts are cups, and just use baker's measuring cups to measure those.

The pigment I would continue to weigh as I use about 4 to 5 grams, and to be a little off on that would yield more varied results.

 

[schyter]

After years of carbon printing -- carefully weighing out 90 grams of gelatin and 60 grams of sugar every time I make a batch of "glop", I think I will just see what volumes those amounts are cups, and just use baker's measuring cups to measure those.

The pigment I would continue to weigh as I use about 4 to 5 grams, and to be a little off on that would yield more varied results.

OT > wow... carbon printing!!! the Queen of ancient printing techniques ... for the moment I limit myself to his younger sisters; gum, cyano, kallitype, argyrotype, Vdb... I'd like to try carbon print, but fear it is too complicated for me.

 

[Vaughn]

Carbon is not all that difficult -- especially if one starts out using fixed out photopaper as the final support (or even many of the cheap inkjet papers). If one has done gum printing, then one is over halfway there.

Let me know if you ever want to give it a go (try it) and I'll be glad to help out.

Vaughn

 

[AgX]

If I ever knew about all these considerations I never ever would have started processing myself:

Once a friend let me have a look at when he processed a film. I then went to a shop, bought a tank, a beaker, a graduate, a bottle of film developer and surfactant each and a bag of Hypo. That's it. I had no darkroom, no changing bag, did not even know about such, no books or such. I'm not sure what thermometer I used.
All went fine and I was pleased.

 

[RalphLambrecht]

I remember my beginnings too.at first I thought.Let the lab do the negatives and I do the prints.Today, I wouldn't trust anyone to do my negatives but myself.

 

[MartinP]

My first processing was the old Agfachrome transparency process. I borrowed a kitchen-jug graduate temporarily, and marked the necessary amounts for my tank on cleaned jam-jars with a felt-tip pen. The actual stuff needed for processing, and even contact-printing, is absolutely minimal and it's both cheap and robust.

 

[schyter]

I develop films for a short time (5 years) and after 1 year I met a photographer Amateur (vice principal of a technical school chemist) who introduced me to this
system for 4 years use with satisfaction. you must believe me when I say that the method had puzzled me too. Try to ask yourself what is the one element in the chain of development, which amateur photographers could not get up until a few years ago. The balance accurate at low cost !!!
today, in chemical laboratories, the most accurate measurements are obtained with analytical balances, and not just with graduated cylinders. This friend with this simple consideration has opened my eyes and led me to try this system.
Obviously, the scales have such low prices compared to the precision I wanted to try. I understand the skepticism for those who for years has been used to operate
with the traditional system; I just want to say do not be so closed and that a test costs very little. I do not want to be likened to a modern Galileo Galilei
in the process one against all. Also because the traditional system works fine!!! Luigi ;/)

 

[MattKing]

I think we should introduce schyter to Umut