September 16, 2015 at 1:32 am #17479
Since 8 month ago, I try to use bromine, and it appears to be extremely difficult. I have too many fails.
First, I tried with bromine water, but after a moment, I understood it’s a too uncertain method : bromine escape too fast from the water, and some areas on the plate are underbromined, while others are too bromined. There is also the risk of moisture for the plate.
So, I stopped this method, prefering the classic one : silica gel saturated with bromine fumes.
I followed the advices of the forum in order to obtain the “post-it” color for silica gel.
The method is far better! I have now very homogeneous results on all the areas on my plates.
But my problem is the following :
– I made some tests to find the good time for bromine. I found 1 mn 20 sec for perfect result. I do another test on a complete plate with this time : perfect result again. The weather was dry and sunny. Temp : 25°C.
But, the day after, I want to do another plate : fail. The plate is underbromined. Almost nothing on the plate. Because the weather changed completely : cloudy, humid, and 19°C. And yet, I added more bromine time : 1 mn 30 sec. It wasn’t enough.
So, the day after, same weather and temperature. I bromine my plate for 2 mn instead of 1mn 30, in order to compensate the low temperature (19°C). Result : too much bromine! The plate is overexposed and typically fogged.
There, I’m lost! Yet, after all those tests, the silica gel still have the same post-it color (yellow). Should I add some red charged silica gel after each use? Even if the yellow color is still the same?
I’m deseperate! Time for bromine change every day! Impossible to have constant result. My problem is that my lab is outside and depend of the weather. One day, it’s 25°C, the day after I have 19°C, etc.
And it’s seem to be impossible to find the good bromine time just looking at the color of the plate. The only way is to check the time. But if this time changes everyday, how to do?
What is your solution?
Attachments:You must be logged in to view attached files.September 16, 2015 at 9:06 am #17481
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.
NWGSeptember 17, 2015 at 7:21 am #17483
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.September 22, 2015 at 7:40 am #17487
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.
NWGSeptember 27, 2015 at 2:26 am #17488
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.
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