9 Mar 2011

Exploring Photographic Chemistry

Lab Experiment

Submitted by Rebecca M. Jones, George Mason University
This set of experiments is a fun way for students to be experience interesting redox chemistry.  I have taught this series of experiments in my first semester junior level inorganic class for the past 5 years.  In part 1, students create salted paper prints with different binders.  Part 2 involves the synthesis of Prussian blue as cyanotypes are formed on paper and cloth.  In part 3, students design their own experiment testing one of the experiment variables from the previous weeks.  These experiments are based upon those developed by Dr. Patricia Hill for the Chemistry in Art workshop in 2005 at Millersville University, in Millersville, PA; permission has been obtained from Dr. Hill to disseminate this adapted set of experiments on VIPEr.  The Chemistry in Art workshop is part of the Chemistry Collaborations, Workshops and Communities of Scholars (cCWCS) program.  This experiment was presented at the 20th Biennial Conference on Chemical Education in Bloomington, IN on July 31, 2008; the attached presentation contains images and additional information that may be helpful when implementing this experiment.
Learning Goals: 
The students taking this course have completed a year of general chemistry and at least one semester of organic.  As a result, most have adequate knowledge to thoroughly understand the chemistry observed.  At the end of part 1, a student should be able to explain the redox chemistry involved in the salted paper print process and identify the light sensitive chemical produced.  Students should also be able to qualitatively compare the results from starch and gelatin binders.   At the end of part 2, a student should be able to explain the synthesis of Prussian blue and qualitatively compare the results from the paper and cloth supports.  At the end of part 3, a student should be able to apply his/her knowledge of photographic chemistry to design a unique experiment which answers a question.  A student should also be able to interpret his/her results and discuss if the results answer the posed question.
Equipment needs: 

Please see the attached file entitled “Supplies and Implementation Notes for Photographic Chemistry

Implementation Notes: 
Please see the attached file entitled “Supplies and Implementation Notes for Photographic Chemistry
Time Required: 
Each part of the lab handout can be completed in one 3 hour lab period. I schedule 3 weeks for the complete set of experiments.
Evaluation Methods: 
I assess this group of experiments by pre-lab and discussion questions completed in the lab notebook and overall lab performance.  I also require a formal written report on Part 3.  This report is in the form of a Journal of the American Chemical Society communication and is graded with a qualitative rubric.  I’ve attached the formal lab report instructions and grading rubric.
Evaluation Results: 
Without a doubt, this is the most popular set of experiments in my inorganic class.  Each year, I receive many positive comments on the course evaluations about these labs.  Students especially appreciate that this chemistry feels “real” and it is easy to visually see the reactions.  The “Design your own experiment” in part 3 has been very well received and there have been some amazing questions answered by these students.
Creative Commons License: 
Creative Commons Licence


My students and I love this lab.  We did only parts I and II during one three-hour lab period, as a "break" after a multi-week synthesis to give them time to write a full report.  We did find that drying the photo paper is absolutely essential or the image will wash away.  I solicited digital photographs from students, made negatives using Photoshop.  I learned a lot about my students by seeing what photos they sent me (pets, friends, family.)  I also provided some public domain negatives for students to choose from.  The students and I talked through the chemistry for both silver halide and cyanotypes.  I hung their completed photography "exhibit" on a bulletin board in the hallway of our science building.

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