KBr while developing

[manojit_pusty1]

<p><a href="

<p>the photographer says he added KBr or potassium bromide to reduce fogging.....please give me the details of its use</p>

[chris_waller]

<p>I usually try 1 gm per litre as a starting point.</p>

[russ_kerlin]

<p>Manojit,<br>

These questions and more can be answered in the <a href="http://www.amazon.com/Film-Developing-Cookbook-Darkroom-Vol/dp/0240802772/ref=sr_1_3?s=books&ie=UTF8&qid=1311379208&sr=1-3">Film Developing Cookbook</a> by Steve Anchell.</p>

<p> </p>

[michael_madio]

<p>Potassium bromide is a common restrainer ... it's typically used in film developers to reduce fog (not always needed) and in print developers. Typical amount is 0.5-1.0g/L.</p>

[Alan Marcus]

<p>Developers are formulated using five major ingredients.</p>

<p>1. Water) A solvent for the ingredients. Sometimes a second solvent is used in color developers; these are alcohols or glycols.</p>

<p>2. Developing agent) A chemical able to liberate metals from their salts. Typically these are organic chemicals, a derivative of benzene, initially a product of coal tar, now artificially fabricated. </p>

<p>3. Accelerator) Development takes place in an alkaline environment. These are borax, sodium carbonate, and sodium hydroxide. The more alkaline the solution, the more aggressive the developer.</p>

<p>4. Preservative) The developing agent is highly susceptible to oxidation. Oxygen dissolved in the waters of the developer will attack and the developing agent reverts to coal tar. This is a staining agent. Sodium sulfite added to the solution retards aerial oxidation and combines with the staining agent rendering it harmless.</p>

<p>5. Restrainer) To be a developer the solution must be able to differentiate between exposed and unexposed silver salts. Potassium bromine is added to restrain the developing action. If not present a development fog results as the developing agent will attack unexposed silver crystals. When developing old films and papers some add an additional pinch in hopes of reducing fog. </p>

[sabir_ahmed1]

<p>The film was Efke KB 21 expired in 1977. I shot the first couple of rolls at the rated speed and developed at the rated times. These rolls were grossly under developed with tons of fog. The results in subsequent rolls improved as I experimented with exposure and development times. However, the persistence of fog was a major dissapointment.<br>

I trawled the web for its solution and found suggestions to use KBr as a restrainer in various dilutions. I initially tried the 1 gm/L and found that it blocked shadow details considerably. For the next few rolls, I reduced the quantity by a fourth and found better results, especially in a single reel tank. The 'pinch' recommendation worked really well. You might want to take a look at the my progress here... <br>

<a href="http://www.flickr.com/photos/sabir/sets/72157622499170557/">http://www.flickr.com/photos/sabir/sets/72157622499170557/</a></p>

 

[manojit_pusty1]

<p>finally Sabir ji......just to get introduced.......I'm Mr.Debanjan Das Gupta's relative.....distant one though.....how did u get to find about ur link being posted by me here?? :) :) have a lot to know about bw film photography frm u.......sndng a msg to u in flickr :)</p>

[manojit_pusty1]

<p>thanks Chris Russ and Micheal for ur responses</p>

[profhlynnjones]

<p>I learned how to do this in the 1950's. I put KBr into a salt shaker and sprinkled it into the developer as needed. NOTE: This is a very powerful cerebral depressant, don't taste it, it might be your last taste test. There was an over the counter drug called "Bromo Seltser" for headaches and hang overs that worked very well,but drinking too much of it killed a certain number of users, discontinued in the 1950's.</p>

<p>Lynn </p>