Benzotriazole

Melvin J Bramley · Apr 6, 2023

Just how accurate do I have to be in measuring the 20 grams of Benzotriazole required to make working solution?
My scale displays only full unit measures?

What is the shelf life of a solution?

Donald Qualls · Apr 6, 2023

If your 20 grams is +- half a gram (as one might assume if your scale will show 19, 20, or 21 but no fractions), at worst your error will be about 2.5% (half a gram heavy or light). You'll normally use 10 ml of 1% solution in a developer, which would mean your intended 0.1 g might be anywhere between 2.5 mg more or 2.5 mg less than intended. I doubt it's enough difference to worry about.

You might, however, consider getting a better scale -- I've got one that cost about $40 that reads in 0.1 g up to 1 kg and then full grams to 3 kg -- and this is after subtracting any tare, so I can still see (for the kitchen one that prompted me to get a second for the darkroom) 0.1g accuracy for my 40 g of coffee grounds with the empty carafe and dripper cone with wet filter on the scale, more than 500 g of tare -- and *still* see tenths when I've tared the grounds and added 800 g of hot water in brewing my coffee (total weight on the scale well over 1 kg, but still reading out in 0.1 g).

Not that this would be a good practice (because what if you overshoot?) but with this Kitchentour coffee brewing scale you could put a 1000 ml beaker filled with water on the scale, hit tare (to subtract the weight of the glass and water) and still see tenths of a gram as you add your benzotriazole to the water.

I can't tell you the shelf life of the BZT solution. I've only used BZT in my darkroom once, and I did so by adding a single tablet of Kodak Anti-Fog No. 1 to a liter of borax-accelerated D-23 made up specifically for sixty-five-plus year old found film.

Melvin J Bramley · Apr 6, 2023

Thank you; you have the most accurate coffee I have ever heard off!
I take your point , a more accurate scale could also be more useful in the future.

Nicholas Lindan · Apr 6, 2023

There is no correct amount of BTA - it's an "add as needed" chemical, so anything from 15 to 25gm would be copacetic. I mix it up in isopropyl alcohol and the quart bottle I mixed 10-20 years ago is still going.

I've had mixed results with cheap digital scales. Some work great, others get flakey, others just show an error code and I get no further. My triple beam Ohaus scale just keeps going and going.

TomR55 · Apr 6, 2023

If I recall correctly, I used to make up a 1% solution of Benzotriazole, which is easier to measure out per liter, and add the proper number of milliliters per spec. Doubtless, some chemists on this site can elaborate on this process?

DREW WILEY · Apr 6, 2023

It seems to last forever in 1% solution, provided you use distilled water and don't get water mold in the bottle. But I generally introduce Benz powder directly into the fresh developer mix. I like reasonably precise amounts, because it does affect film speed as well as film curve shape. As far a 10 grams worth goes to produce a 1% liter solution, an error of a gram, plus or minus, won't make much difference. The typical Ohaus beam scale is easily accurate within 1/10th g.

albada · Apr 6, 2023

You must be mixing a huge amount of something.
Most formulas specify less than one gram of benzo per liter.

Mark

koraks · Apr 7, 2023

albada said:
You must be mixing a huge amount of something.

Indeed.
20g of BTZ will make 2 liters of 1% stock.
I use BTZ only very rarely and have recently used up the last of my 100ml of 1% stock. That lasted me for about 5 years if memory serves. 2 liters of stock solution would outlast me. Good thing that it keeps well!

Don_ih · Apr 7, 2023

You can't make more than a 1-2% benzo solution in water.

DREW WILEY · Apr 7, 2023

I corrected my previous post. Thanks, Koraks and Don. I had just walked in from mixing developer in the darkroom using 2g of restrainer, and somehow inadvertently had 2 something or other stuck in my head.

john_s · Apr 7, 2023

Don Heisz said:
You can't make more than a 1-2% benzo solution in water.

But more will dissolve in alkaline solution. This graph copied from a website of a company that supplies it for industrial purposes (name forgotten, sorry)

You could use one of the ingredients of your developer to make the stock solution alkaline.

koraks · Apr 7, 2023

john_s said:
You could use one of the ingredients of your developer to make the stock solution alkaline.

It use e.g. ethanol instead of water to dissolve the BTZ in. A very concentrated stock can be made this way. I'm not sure how it would be useful, but it could be done.

Don_ih · Apr 7, 2023

john_s said:
But more will dissolve in alkaline solution. This graph copied from a website of a company that supplies it for industrial purposes (name forgotten, sorry)

You could use one of the ingredients of your developer to make the stock solution alkaline.

For photographic purposes, there doesn't seem to be any value to having a stock solution of greater than 1%.

I do find it interesting what will make things dissolve, though.

Melvin J Bramley · Apr 7, 2023

Don Heisz said:
For photographic purposes, there doesn't seem to be any value to having a stock solution of greater than 1%.

I do find it interesting what will make things dissolve, though.

Photographers Formulary suggest; mix 10 grams to 500 ml of distilled water , add 30ml of this solution to 1 litre of developer.
If I can manage with less thats good.
I have about 1000 sheets of Agfa and Kodak RC paper with a slight fog.

Don_ih · Apr 8, 2023

Melvin J Bramley said:
I have about 1000 sheets of Agfa and Kodak RC paper with a slight fog.

I keep a bottle of Benzo solution and add to working developer to reduce fog in old papers I use. It may or may not work with RC paper, since that may have incorporated developer. That seems to inhibit the impact. You can also keep a 500ml bottle of water with a tablespoon of sodium carbonate in it to add a bit to the developer to boost its activity. You can add more than 30ml of the benzo solution - but I'd suggest adding it about 5 ml at a time. You can't take it out and too much of it seems to kill developer completely.

Another way to deal with the paper fog is Farmer's reducer.

Melvin J Bramley · Apr 8, 2023

From an old post.
No mention of paper type.
Promising!

Effects of using Benzatriazole on fogged paper.

I am trying to rescue some paper by adding Benzotriazole to the developer. Can you tell me what the "side effects" will be? Influence on contrast, printing time and developing time. Upto which volume of a 1% solution in 1 liter of developer will be worth trying? I am using Ilford PQ universal...

www.photrio.com

John Wiegerink · Apr 8, 2023

I always mix it as a 1% solution in distilled water. Much, much easier to work with, and it's always mixed and ready to go on the shelf.

BobUK · Apr 8, 2023

Melvin J Bramley said:
My scale displays only full unit measures?

I assume that a full unit on your balance is 1 gram.
As you are in Canada your Canadian Cents can be used to measure 0.1 gram.

You need good condition Canadian Cent coins.
Year 2000 - 2012 Canadian cent should weigh 2.35 g
Year 1997 - 1999 " " " " 2.25 g

So if you put one on each side of your balance, one side should be heavier by 0.1 g

Accuracy problem solved without buying new balance scale.

Canadian Circulation Coin Physical Specifications

Click on the link above to see other coin weights.

I hope this helps with the weighing of small amounts.

MattKing · Apr 8, 2023

I can't remember the last time I saw a Canadian penny!
I guess it has been 11 years since they were actively circulated.

Don_ih · Apr 8, 2023

BobUK said:
I assume that a full unit on your balance is 1 gram.

I think a safer assumption is he has a little digital scale, not a balance at all.

And, unfortunately, pennies are a scarce commodity here, (Matt beat me to it).

BobUK · Apr 8, 2023

Have a look down the back of the sofa or armchairs, you always find loose change there.

Don_ih · Apr 8, 2023

BobUK said:
Have a look down the back of the sofa or armchairs, you always find loose change there.

Oh, I have a big jar of pennies. I'll never run out. I have an Ohaus beam scale that wouldn't zero - I used pennies under the dish to make it right (Ohaus uses washers and what appears to be buckshot).

Mick Fagan · Apr 8, 2023

Don Heisz said:
Oh, I have a big jar of pennies. I'll never run out. I have an Ohaus beam scale that wouldn't zero - I used pennies under the dish to make it right (Ohaus uses washers and what appears to be buckshot).

So that is what is called buckshot then?

I recently pulled my triple beam Ohaus copy apart for a service on the Speed Dial on my Speed Dial Balance. After 30+ years of hard work, used every day multiple times in a work environment for close to 20 years as well as after hours measuring my photochemistry, the knob wouldn't rotate easily and eventually started to seize up.

Pulling the whole shebang apart I found large mudguard washers and small gunshot like pellets. After cleaning everything I reassembled but didn't add the pellets, thinking they were an oversight in the factory. Nope, they were needed.

Don_ih · Apr 9, 2023

Mick Fagan said:
Nope, they were needed

Yeah, I guess they didn't even try to balance the material mass on either side of the fulcrum. The washers get it close and the pellets zero it out. I have one I got for $2 that was missing the zeroing knob and the dish was bent. I took the dish off to straighten it and that's when I saw the washers and pellets. I tossed enough pennies in there to make it zero without the knob.

Melvin J Bramley · Apr 9, 2023

FWIW,
I tried the Benzontriazole at the recommended dilution and using 30 ml per 1 litre of developer.
The Agfa paper cleaned up nicely as did the single weight Kodak Poly contrast rapid.
The Kodak Polymax fibre 'fine art' was nowhere near being salvageable.
The Kodak Polymax RC improved and maybe more anti fog will do the trick!

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