The John and Marcia Price College of Engineering
19 Engineering Meets Photography Through Vitamin C and Silver
Abigail Stringfellow
Faculty Mentor: Roseanne Warren (Mechanical Engineering, University of Utah)
Background
Recently, Professor Joe Marotta from the Department of Art & Art History pressed a lily onto a piece of photopaper, then developed it, without light exposure through the process. When a permanent image remained, he and Professor Roseanne Warren from the Department of Mechanical Engineering determined that it occurred due to the chemical reaction between the silver in the photopaper and the L-ascorbic acid (vitamin C) in the flower. Though ascorbic acid has been used as a developing agent for light-exposed silver-based paper before, Professor Marotta and Professor Warren’s findings are the first to show this result in the absence of light [1, 2]. L-ascorbic acid is widely used industrially and commercially. Among its uses are as an additive or preservative in food, a medical treatment, a measurement of quality in produce, and a crop spray in agriculture [3-6]. Due to the many applications of ascorbic acid, ascorbic acid detection methods are in demand in both consumer and industrial markets. Approaches to detection include, among others, titration [7], fluorescence [8], and electrochemical [4]. Out of the current options, none are low-cost, and most use specialized equipment, making them unsuitable for the average consumer. This project investigates the chemical reaction between ascorbic acid and silver halides with the aim to develop a low-cost ascorbic acid concentration sensor. In the past weeks, I have determined a preliminary grayscale to use in the sensor, which relates ascorbic acid concentration to image darkness. Type of photopaper, time between application and development, pH of solution, addition of copper ions, and ascorbic acid concentration were experimented with in this model.
Methods
Using the statistical analysis program JMP, I produced a Design of Experiment based on these five factors. In each test, 35 milliliters of pH buffer four, seven, or ten was added to 100 milliliters of deionized water. Between four and eight grams of ascorbic acid was stirred in. A ratio of between 0:1 to 1:1 of cupric sulfate to ascorbic acid was included in each solution. Solution pH was recorded using a pH meter. Each solution was applied to one of three types of Ilford photopaper—Multigrade Resin Coated (RC), Multigrade Fiber Based (FB), and Ilfospeed Resin Coated (IS)—using a needleless syringe. After being left without light exposure, the tests were developed after two, four, or six hours. Following development, each test was scanned and evaluated using the program ImageJ, which gave a grayscale score 0 to 255, with 0 as black and 255 as white. Tests 11, 18, and 22 (Fig 1-3 respectively) are shown below to show typical outputs of the experimental runs. A range of gray values can be seen alongside the added calibration black and whi