Creating a black and white emulsion

<p>for say creating a ISO 200 or 400 speed emulsion what chemicals would you need? I know silver halide is one way to create an emulsion but how can you effect the light sensitivity? </p>

<p>I think this was asked right here.</p>

<p>http://www.photo.net/black-and-white-photo-film-processing-forum/00GJVR</p>

<p>Initially, silver halides (silver iodide is the most sensitive) is mainly sensitive to blue light. I recall a lab exercise from a 1940's photo textbook that actually outlined a procedure, but again, nothing anywhere near ISO 200. IIRC, this exercise yielded what would be the equivalent today of about ISO 5.<br>

If you haven't checked yet, be sure and go to the link that Larry posted. </p>

<p>Check out this thread from Apug (Analog Photography Users Group):<br>

http://www.apug.org/forums/forum205/<br>

Best regards,</p>

<p>/Clay</p>

<p>For 200 to 400 speed, you would be getting very sophisticated, would need controlled crystal growth. For slow emulsions for glass plates, it's more practical. The world expertise in putting the "how to" in the public domain hangs out on that APUG forum.</p>

<p>You may find this book useful :- Silver Gelatin: A User's Guide to Liquid Photographic Emulsions by Martin Reed & <a href="http://www.amazon.co.uk/s/ref=ntt_athr_dp_sr_2?_encoding=UTF8&search-alias=books-uk&field-author=Sarah%20Jones">Sarah Jones</a> ISBN 1902538153, but check what price you need to pay - in the UK it ranges from 20GBP new to 120GBP used!</p>

<p>We start by mixing a 10% solution of silver nitrate to a solution of gelatin laced with potassium chloride. In this soup, tiny silver chloride crystals form and grow. We mix in a room illuminated by a dim red lamp as the solution has some sensitivity to blue light.</p>

<p>The solution is allowed to stand (digest) at a temperature of about 90 degrees Fahrenheit for several hours. This action allows some of the small crystals to dissolve and reform into larger crystals. During this stage (ripening) a sensitivity gain comes about.</p>

<p>Finally, more gelatin is added. Gelatin enters into the reaction because it contains impurities, which further increases sensitivity. The solution is cooled forming a stiff jelly.</p>

<p>The jelly emulsion is now shredded into noodles, washed to remove residual chemicals. Hardeners and sensitizers are added plus secret stuff. </p>

<p>Of the three salts of silver, silver iodine has the lowest sensitivity followed by silver chloride and then silver bromine.</p>

<p>Films and papers are blends of the three silver salts. These crystals when pure have little or no sensitivity to light. Impurities must be added to alter their sensitivity. This process is called doping. </p>