How do you manage to have repeatable results with bromine?

[nawagi]

T-

As you have learned, Bromine time changes based on weather, temperature, the color shirt you’re wearing, etc. It is different every day.

I run a test plate at the beginning of every shooting day to determine my Bromine time. I use a set of vertical masks, each exposing 1/4 of my plate, after fuming Iodine to my standard color choice (rose-magenta). I fume the masks to Bromine for 2, 4, 8, and 16 seconds – then expose and develop my test plate. The best Bromine time for the image is easily selected off the test strips.

The test plate is also an excellent ‘rehearsal’ for multiple steps Dag creation requires, and to ensure all the supporting chemistry is behaving properly.

Selecting your Bromine time this way adjusts for all the variables you can’t control – including the strength of your Bromine. Your image of Brominated Silca gel is good – although my working color is lighter than yours.

Iodine times can be very reliable based on your eye and the plate color. Plate color does not work for Bromine – it is a timed reaction with minimal visual clues.

This past weekend, plates fumes to 1st rose-magenta needed 6 seconds of bromine time. Next weekend it will be different as the humidity has dropped considerably here.

NWG

[titisteph]

Thank you, nawagi, for your fast answer!
So, I understand there is no real and easy way to obtain repeatable results with bromine… It’s a bad news for me…
I should be forced to do everytime a test plate just for bromine… exactly what I don’t want to do!

Dag is so incredibly difficult to practise!

But there is something I don’t understand : when you put your silica (charged with bromine-yellow color) into your fuming box, prior to doing a first test… how can you be sure there will be the same bromine concentration for the second test one hour later?

Is there a risk to have lower bromine concentration into the box after a moment, even if the color of the silica doesn’t changes? Is the yellow color is a good predictor?

Thank you for your help.

[nawagi]

T-

Changes in Bromine box strength arise from time, heat and exposure to the air. I find almost no change over an hour’s time, and no change over during a working day of 8 hours (or 8 plates at my snail-like pace). Significant changes occur from one week to the next, or if the box has a big temperature swing. I keep my boxes in my garage, which is hotter in the summer and colder in the winter. I must bring the boxes inside to stabilize at my darkroom temperature for 24 hours before I use them- but that constant temperature leads to consistency.

It becomes very challenging when sensitizing plates in the field as temperature can vary.

I am sympathetic to your frustration with having to do a test plate each time. I changed my attitude about tests a while ago. Yes they take time and materials that you would rather use for a beautiful dag – but that test is what
makes the dag beautiful. And one test in the morning is a small price to pay for a day of good plates – even two days if the weather holds.

NWG

[titisteph]

Hello Nawagi,

Thank you so much for your help!

I understand it’s very usefull to have a lab with quite constant temperature.
Unfortunately, mine is in my garden, and impossible to warm in winter (no door, too much holes!) So, I’m dependent of the weather and it’s very difficult to progress like this.

And under 12°C, (mid october), it’s over for me, iodine doesn’t want to sensitive my plates. I must wait for spring to continue.

[Author]

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