Public Lab Research note

This is an attempt to replicate an activity.

H2S Photopaper Processing notes

by ewilder | June 17, 2014 01:44 17 Jun 01:44 | #10578 | #10578

Developing the Strips – September 2013

We had access to a darkroom and began by brainstorming the best way to develop each set of strips. Everything needed to be arranged in advance, as once the lights were off, it would be much more difficult to identify each strip, read the writing on each canister, etc. We began by writing the identification tag of each strip on two different post-its in black sharpie. The locations were abbreviated as follows: Elk Basin (EB), Deaver (D), Hamilton Dome (HD), and Legend Rock (LR). The strips from each location also received a number designating their precise placement, and the first round of tests was designated with a lower case “a”, the second round with a lower case “b”, and so on. So, EB5a corresponds to the fifth placement at Elk Basin during the first round of rests. Controls were labeled with a lower case “n” following the location abbreviation (e.g. EBn = Elk Basin control strip. We arranged the post-its on two different photo drying racks and secured them with a thumbtack, then placed the unopened canisters containing the strips next to the post-its on the first rack.

We placed the second rack, with an additional thumbtack to the left of each post-it (to pin the strips to the drying rack once each is developed), next to the first rack.

We prepared a developing station for each person with a pair of tongs and two trays: one containing fixer, and one other water. We decided that the fixer would always be to the left, and the water always to the right. Paper towels, and disposable gloves were also readily accessible. We then turned off all lights, except for the red safe light. Since we had four people in the darkroom, we decided that one person (Sara) would open each canister in order and pass the strip to the developers (Lauren, Jacob, Elisabeth) and along with the post-it that identified it (i.e. as EB1, EB2, EB3). We placed the post it and the empty canister from the first tray above or below its corresponding post it on the second tray. Sara then set the darkroom clock (glow in the dark numbers and hands) to six minutes, and we would each put the strip into the fixer, making sure that it was completely submerged. After six minutes, we took the strips out of the fixer and placed them in the water bath, holding them carefully and swishing them around in the water. After about 30 seconds, we dumped the water, refilled the tray, and repeated the process, for a total of 3 washes. We then pinned the strip next to its corresponding post it on the second drying rack and repeated the process until all strips had been processed.

The strips were left to dry overnight, and then, using double sided tape, placed on an index card that identified each strip. An index card was created for any missing strips, with the word “missing” written in the center of the card where the strip would have been taped. The index cards were stacked (with a blank index card between them) and placed under a heavy object to flatten them. All index cards were then placed in order, scanned, and put into a filing cabinet for safekeeping. Post-its were put inside of the canister they referred to, and canisters were collected and placed back in the bag or envelope that they had arrived in.


Thanks for posting! Looking forward to watching this technique progress!

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Hi @ewilder - We're going to do an OpenHour on exploratory hydrogen sulfide monitoring methods Monday, January 8th at 8pm ET/ 7 central. Hope you'll consider joining on!

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