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Barry Thornton's two-bath question about time and temperature

That’s really interesting, especially your second paragraph. Thank you! It explains why I sometimes struggle to achieve satisfactory mid-tone separation when printing these negatives. One can’t have it all ways, of course.
 

I ordered some BTTB developer, so am going to give it a try. Firstly, I want to expose a step tablet to generate a curve or two..

AA suggested, that with the long straight-line regions of the thin emulsion films that were available at that time, to develop in bath A for just 2-3 minutes with "constant" agitation........I wonder would this be problematic with T-grain films. Three minutes in bath A is less than anyone has mentioned for bath A in this thread and all seem to state using some method of intermitttent agitation in their bath A............maybe that's accurate, but I didn't check 5 pages of posts. BT recommend some form of intermittent agitation as well in the first bath. I wonder has anyone following used continuous agitation in their bath A, either T-grain emulsion or otherwise.
 
Yes, irrespective of film type, I always do continuous inversions in Bath A. That is because I came to BT2B via Emofin, as I explained upthread somewhere, and it worked for me. In Bath B, I do as little agitation as I dare. That's because I read what Thornton said about adjacency effects!

I haven't used T-grain emulsions for ages, but I did use some Delta 100 a few days ago, dev in BT2B for 3.5+3.5 min at 22 deg C. This is the result. (The obvious lack of sharpness is because I was handholding at 1/15 sec.) Evidently such thin emulsions do carry enough developer.

 

There's a lot of debate/confusion about how much/how often to agitate in both bath A and B, and much of what I've read leads me to think that it doesn't much matter as long as you don't wander into the territory of extremes (no agitation/constant, vigorous agitation).

Ultimately, I think it's worth your while to conduct your own experiments to see what works for you. Expose a roll of your chosen film with the same image (maybe bracket up to one stop plus and minus) and cut the roll into pieces and develop each differently to give you something to make comparisons.

That said, I have not found any problems using "T-grain" (Kodak) or "Core-shell" (Ilford) films in the BTTB developer. I typically use 4 + 4 minutes at 68-71F with 10 seconds agitation every minute in bath A and two inversions every minute in bath B. In some instances I want more contrast for a particular result and so I will add more time to Bath A: up to 6 minutes in some cases. Not agitating the tank at all will almost certainly result in streaks, bromide streamers and (with 35mm film) sprocket hole marks. But again, I suggest you perform your own tests to see where the sweet spot lies for your needs.
 

The time and agitation in bath A will determine the final contrast. It is best to think of bath A the way you would think about single bath development - all the same variables since the Barry Thornton bath A is a functional developer (virtually the same as D-23). Therefore the development time in bath A to produce a target gradient will tend to vary depending on the film. I think 2-3 minutes would be a minimum. I didn’t do less than 3 minutes in my tests (which were mostly FP4 but also some TMX and Delta 100) but there’s no reason not to experiment. As with any developer the more agitation you give in bath A for a given development time, the more development (ie contrast) you get. I suggest starting with whatever your standard agitation technique is.

I also suggest at least 3-4 minutes in the second bath regardless of agitation or the composition of the second bath. Simply put, you want to make sure development in the second bath always goes to exhaustion/completion. Development is rapid in the second bath but by you don’t have anything to lose by giving it some extra time.
 

This is the most insightful and valuable post I’ve seen in ages. Thanks.
 
Chuck_P said:
I ordered some BTTB developer, so am going to give it a try.......
Click to expand...

Sorry...............when I said this, I should have stated more clearly that I ordered the metol, sodium sulphite, and sodium metaborate to mix the BTTB. However I still need a scale for measuring the dry chemical weight, but haven't worked out which one I should get.
 

About 7 years ago I bought a generic digital scales (American Weigh Scales brand, Digital Pocket Weight Scales, made in China of course lol) on Amazon for $18. It has served me well in the years I have owned it, without any issues whatsoever. I think that the trick (if you can call it that) with these pocket sized digital scales is: NEVER drop them, or you'll eff them up. I've been very careful not to bang or drop mine, so it still works perfectly 7 years later.

It's easy to look at an $18 device and think "that's gotta be junk" and often, you'd be right. But I have relied on this to measure my chemistry and it has been reliable and (apparently) accurate. I measure amounts as small as 0.25 grams of Phenidone and have no difficulty trusting the measurements. I suggest this is a reasonable scales to choose for your purpose.
 

like what retina_restoration said, really any scale that can go down to 0.1g should be good. i have two - one that goes down to 0.01g and one that goes down to only 1g. the 1g minimum one is used for weighing large amounts of sulfite needed for this while the smaller one is used for the metol and the metaborate.
 

You don't need a scale. I use the teaspoon method and there's a conversion chart in the back of The Darkroom Cookbook.
 
jim appleyard said:
You don't need a scale. I use the teaspoon method and there's a conversion chart in the back of The Darkroom Cookbook.
Click to expand...

To make Thornton 2 Bath you can easily use the teaspoon method, certainly. It is my experience that once you start mixing your own simple chemistry - like BTTB - it won't be long before you'd making your own D-76 or Xtol clone, or maybe Pyrocat HD. At that point, you'll need scales for sure. I like to plan ahead When you can acquire a competent digital scales for under $20, why not have one available?
 
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The only other question that comes to mind is.......would a scale that weighs only up to 200 to 300g basically cover just about any developer that I may want to experiment with beyond BT2B or should I up the capacity of the scale to cover future needs. I've no idea at the moment what other developers that I may want to try.
 

one of my scales is a kitchen scale going to 5kg. thats kind of overkill but it works for my needs. 20 bucks at target.
 

It's going to be a rare thing that you should need more than 100 grams of any developer component. The scales I use has a maximum of 100 grams, and I rarely need more than 100 grams of something (that's almost always Sodium sulfite, the ingredient you're likely to use the most of in any developer) and if I do, I measure 100g and then a second amount to get what I need. (Occasionally I need to weigh out 200 grams of Sodium thiosulfate, so I measure 100 grams twice: no big deal)
 
My usual balance does up to 100g and reads to 0.01g (one part in 10,000). I have another that does 500g to 0.1g (one part in 5,000) that I do not use much.

These little electronic balances are just that - small. I find that for most photographic chemicals anything much over 100g is going to require a container that is too big for the top - I can't see the display. The densest compound I might weigh would contain gold (for toner), and I would be using precious (sic) little of that!
 

That looks like the type of scale I will be looking into buying next.

The first US Balance brand scale that I bought five years ago is a good one. Early this year I bought a second scale of the same brand name and it is quirky. Calibration doesn't always go beyond the PASS point, measurements are also on the jumpy side and, as one example, when I am measuring out the sulfite I cannot get the reading to go exactly to 80.0, no matter how much I try. It will go to either 79.9 or 80.1 grams. Why that a scale doesn't want to go to 80.0 is anyone's guess. Gremlins at work?

The first scale I would rely upon but for anything like phenidone, bromide, or if I ever use BZT, a scale with two decimal places would be better.
 
This for $40 is what I'm leaning toward, seems like a decent scale, but how would I know, lol.

Digital Platform Scale, 300 g x 0.01 g

This compact digital platform scale is perfect for labs, with 0.01g sensitivity, 300g capacity, 10cm weighing surface, LED display & backlight. Order today!
www.homesciencetools.com
 
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Hey, that is the same place where I got my formaldehyde from! The reviews look mostly positive. Bookmarking this one.
 

that is the scale I use. got it from amazon years ago and works great. dont think i paid that much, more like half that, but it was about 8 years ago. works great, but like mentioned above, dont drop it or it does get messed up.

john
 
There are three on Amazon that look identical to the one at the Science store. Prices range from $13.99 to $17.99, one of them is listed at 500 gram capacity.
 
This web page might help: http://dotinthelandscape.org/darkroom/balances/ Fair notice: it's one of mine.

I used to have to weigh chemicals to 4 or 5 decimal places for analytical work in a lab. Only worrying about 2 places is a great relief! My main concern is that I can reproduce my weighing these days.
 
My last two chemicals arrived today from Photographer's Formulary. Just one question regarding the sodium metaborate, it arrived a bit chunky when I opened it. Is this normal for this chemical? The metol and sodium sulphite anhydrous seemed normal. I have reviewed the SDS sheets for each.

Also, any mixing or preparation tips I should know?
 

Only see post #111 above ; and the usual thing about putting in a pinch of the sulphite before dissolving the metol, to minimise oxidation. Add the rest of the sulphite when the metol is completely dissolved. And don’t use the developer the same day.
 
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