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Better to be safe then sorry, so...
I have the liquid pre-mixed (not in glycol)
For 1:1:100 stock working solution
I am going to mix 10ml each of the solutions (A&B) into 1000ml distilled water.
Is room temp 68F acceptable or should I pre-heat the water prior to adding the solutions?
Thanks, Dave.
Room temperature of 68ºF is fine.Quote:
Originally Posted by David Brunell
Main issue in mixing is to avoid contamination of Stock A with B or of Stock B with A. One way to do this is to use separate beakers and/or syringes for measuring Solution A and Solution B.
Sandy King
Perfect, I measure and add them to the water independently...
Thank you Sandy, I am looking forward to using this.
David,
I'm not sure how critical it really is, but I think best practice is to add the carbonate (part B) to the water, stir well, then add the part A and stir again. I always add the developer to the full volume of solution I want to use. For instance, if I'm making up 500ml of solution, I add the part A and part B to 500ml of water and ignore the slight error in dilution. This has never caused me the slightest problem, and it removes a step (final topping up) from the mixing. Granted, my developers are more concentrated, but I think the same principle applies to Pyrocat HD. As Sandy says, the really critical thing is to avoid contamination of the part A by part B, which would ruin the stock solution in a very short time.
Thats good to know as I am goint to be doing 500ml batches for 120 roll film. Sounds pretty straight forward...I have a feeling this is going to be one of those things (developer) that I should have discovered long ago.
I am actually souping up right now, just as Jay mentioned. As Sandy says, contamination should be avoided! This evening i am going to develop a couple of sheets that i shot without my light meter. I drove for over a 120 miles only to discover i had left my light meter at home. The good thing was, the film in my holders, Efke PL 50 has been a staple of most of my work. I hope every thing will be ok! I will do a couple of test first. Great stuff!
Nah, don't worry about it you will be fine...Another photographer I read about ran into a similar situation and his print turned out just fine.Quote:
Originally Posted by tautatis
http://www.anseladams.com/Articles.asp?ID=145
Think of it as an opportunity to determine just how essential a light meter is for you. A light meter would be way down on my list of essentials. I hope you find the same thing. Good luck!Quote:
Originally Posted by tautatis
David,
If you are learning how to mix chemicals, then learn to do it the correct way: One always tops offto the final desired volumn and not the reverse. This is something that you learn in HS chemistry. "Do it once, do it right."
The only time that you add to the final desired volumn is when you do percentages. For example adding 10 grams to 100mL of water for a 10% solution.
Thomas
Thanks for the tip Thomas. I don't know what a chemistry classroom looks like for what it is worth! Got it...Quote:
Originally Posted by tgtaylor
700ml's water, A then B individually then top it off with 300ml's water. Done.
Thanks
tg,
I agree with you wholeheartedly about doing things right, however, topping off when for mixing a developer like Pyrocat, PMK, or Jay's 510 Pyro, is simply not needed. What is important is consistency.
If you standardize on, say, 500ml water (carefully measured out) with (for me) 10ml PMK solution B and 5 ml PMK solution A (also precisely measured out with syringes) to make 515ml of working solution, and if you test with this mix and calibrate EI and developing times to this mix, then, indeed, you have no need to top off and, as Jay observes, you have removed a step from the mixing. Just always do the same thing when mixing.
I, and a whole lot of other careful photographers, mix developers this way, and I think the OP is safe with that method as well as long as he is consistent. On the other hand, if he chooses to top off, and remains consistent with that, then he'll be fine too.
And, BTW, it is necessary to top off when making percentage solutions, since the dry chemical you add to the water will increase its volume somewhat. If you start with the final volume, you'll end up with too much after adding the chemical...
Best,
Doremus
Not to mention that my 1 liter pyrex beaker is marked +/- 5%, so I could have anywhere from 950ml to 1050ml when I fill it up...
No one has mentioned temperature. Pyrocat will work at 68 deg, but the times will be long. I believe the suggested temperature is 75 deg. F. Often on this site the complaints about thin negatives have been determined to be caused by low temperatures coupled with "suggested" times.
Tom,
The advantage of not topping up is in simplifying the mixing. The advantage of topping up is in precision. Understanding the degree of precision required, or possible in any process, comes with experience. If one can't measure the precision in results, it's wasted effort, and simplification trumps precision. When teaching a concept, as in a high school chemistry class, these practical issues are not the point. Mixing and using a developer is a practical matter, where simplicity and consistency are more important than rote learning. Since I pointed out the error I was recommending, and my reasons for it, I don't feel I've led anyone too far astray. If you're more a letter of the law, than a spirit of the law kind of person, by all means top up, but your own error in recommending that topping up is not necessary when making a percentage solution illustrates the downside of rote learning compared to a fuller understanding of the underlying concepts that predict the consequences of deviating from standard practice.