Photo Emulsion Test no. 4

April 30, 2015 

Researchers:Kevin Pomerleau/ Daniel Chiaccio
Room Temperature: 65 degrees F
Humidity: Dry

Materials: Macdermid Plus 8,000 Universal Resistant Emulsion, 17x 15″ screen, Speedball Screen printing ink with extender, Exposure unit, Opaque Black Trash Bag, 2.5 lb paper weights

Abstract: To see if the length of exposure time causes the emulsion to harden into a solid dark blue color as obtained in test no. 2 and if that is able to produce a greater variation of mid tones with less blowing out.

Procedure: Using a 14″ scoop coater, we coated a 17 x 15″ white 195 mesh count screen. After letting the emulsion dry for 45 minutes under ventilation, we exposed a pre made transparency using both halftone and text (the same transparency from test no. 1) by placing the transparency, emulsion side up, onto the exposure unit with the emulsion coated screen face down over it (emulsion to emulsion). We then covered the entire unit with the opaque black trash bag and the 2 paper weights and set the exposure time for 10 minutes. Once the exposure was finished, we removed the weights and trash bag, and walked the screen to the washout booth (in a non light safe room) and washed the screen out.

Conclusion: Due to the lack of detail obtained in the final print, we concluded that the exposure time was set too high. Although the text printed clearly, there was a lot of detail lost in the mid tone images. Majority of the detail in the koala had been lost and the lines around the circles in the corners of the image had completely disappeared. This was due to an over exposure of the screen. As opposed to moving to a longer exposure time, we learned that an ideal length of time would be somewhere between 5 and 10 minutes. For our next test we will expose the Macdermid Emulsion for 7 1/2 minutes, and see how much detail will be obtained.



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