Stouffer Instructions for Puretch Exposure
1. Set your contact printer or vacuum frame to make several trial exposures on separate sections of film, with each exposure for a different length of time. Laminate a piece of Puretch that is the width of about 6 Stouffer strips. Use a piece of black plastic and cut a window just large enough for the Stouffer and tape it at the top. Make the plastic wide enough to cover previously exposed strips and move strip over for each test.
2. Make three or more exposures: one determined by past experience or the exposure normally used in daily production, one for less, and then one for more. It may be necessary repeat this testing procedure using different exposure times.
3. Process the test negative for the time and temperature recommended in the Puretch instructions. It is important to keep processing consistent.
4. Examine the step tablet image on each of the negatives. Select as the best the negative in which one of steps 6-9 is the last step visible, with step10 and above being plate only. Step 7 will be the aim point for normal copy. Use a solid #4 - faint #5 for fine halftone work (pictured right). There are many different ways for exposing plates. There are an abundance of different exposure systems and processing techniques. The one constant is the step tablet. Use the step tablet as a benchmark for all exposures to achieve accuracy and repeatability. To find the exposure factor to hold more or less steps on a Stouffer 21 step transmission wedge follow the Exposure Correction Table below.
Optimum Puretch exposure for halftone shown above after exposing and developing a Stouffer 21 step wedge. Step 4 is 'solid' while step 5 is somewhat thinner and step 6 is starting to break up.