How To Use A Dual Exposure Calculator for Screen Making - Post Thumbnail

How To Use A Dual Exposure Calculator for Screen Making

chromaline exposure calculator for screen printing

When making screens for screen printing, a proper exposure can save you hours of frustration on press. At least 90% of stencil failures can be traced back to exposure times.

Chromaline's Dual Exposure Calculator eliminates miscalculated exposure time with three kinds of quality checks: determines your correct exposure time, performs a print quality check and determines halftone quality. This easy, user friendly tool is great for the beginner screen maker as well as the advanced screen maker. Below we outline exactly how to use the Dual Exposure Calculator.

WATCH VIDEO: Why Proper Exposure Matters (COMING SOON)

How To Use Chromaline's Dual Exposure Calculator

This calculator doubles as a basic Step Test AND One Step calculator. Here is a step-by-step guide on how to use each side.

One Step Exposure Test

The left side of the exposure calculator has a special filter that is ideal for diazo and dual cure based emulsions. Follow the instructions below or watch the video, Dual Exposure Calculator Part 1: Step Test.

  1. Place Calculator On Screen: Place calculator on the coated screen with the emulsion side of the film in direct contact with the emulsion on the screen. The small filter on the calculator must not come in contact with the emulsion on the screen. This will ensure that the calculator will be emulsion-to-emulsion.
  2. Expose Your Screen: Expose the screen for twice the time you estimate is the correct exposure time for your UV lamp. Record this time and call it the TEST EXPOSURE TIME.
  3. Develop Your Screen: Develop the screen, then dry as normal. Wet screens will be swollen and misleading.
  4. Analyze Results: Study the line resolution targets on stencil to determine correct exposure time. Look at each pair of line resolution targets and pick the clearest, sharpest image. Record the number in-between the best pair and go to step 5. If it is impossible to choose a “best” pair of images, do one of the following things, depending on what you see. If all line resolution targets are “washed away,” start over at step 1 and double your original test exposure time. Record the new, longer exposure time. Sometimes you won’t find a pair of targets with clear, sharp lines. For example, targets numbered 0.50 may be too filled in and targets numbered 0.33 may be too washed away. Use a number that would be in-between the targets that weren’t quite right. In the example given, 0.40 would work to give the correct exposure time.
  5. Determine Exposure Time: Use this formula to determine correct exposure time: Best Target Number x Text Exposure Time = Correct Exposure Time. For example, 0.50 x 2 minutes = 1 minute.
  6. Confirm Exposure Time: Make a new stencil of the calculator using the correct exposure time established to confirm results.

Step Test Exposure Test

The right side of the exposure calculator is ideal for photopolymer emulsions. Follow the instructions below or watch the video, Dual Exposure Calculator Part 2: Exposure Calculator.

  1. Place Calculator On Screen: Place the Chromaline Exposure Calculator emulsion side against the coated screen. Use cellophane tape to hold it tight to the screen.
  2. First Exposure: Determine a base exposure to start with. This is an educated guess. For example: You think that the emulsion you are using will expose in 30 seconds. Expose the screen to the UV light source, for 30 seconds.
  3. Second Exposure: Next, cover up image #2 through #5 with a black UV opaque paper and expose the Chromaline Exposure Calculator (do not remove the taped calculator from the screen). Re-expose the calculator for X amount of time (say, 10 seconds).
  4. Third Exposure: After the exposure, move the paper down to the next step #3 and expose again for 10 seconds.
  5. Fourth Exposure: Repeat again on the next step #4.
  6. Done Exposing: You’re done. What you will end up with is a screen with 5 exposures of 30 seconds #5, 40 seconds #4, 50 seconds #3, 60 seconds #2 and 70 seconds #1.
  7. Evaluate Results: Develop the screen and examine the image. Select the image that looks the best. For example, if #4 looks best, 40 seconds is your exposure. If they are all closed up the test must be redone at a shorter base time. If they all wash away the base time must be increased.

Additional Tips For Proper Exposure When Making Screens

  1. Maintain Consistent Conditions: Ensure that the temperature and humidity levels are consistent in your exposure area. Variations can affect the emulsion and exposure times.
  2. Clean Equipment: Regularly clean your exposure unit's glass and UV bulbs. Dust and debris can block UV light, leading to underexposed screens.
  3. Regularly Test Bulbs: UV bulbs degrade over time. Regularly test and replace them as needed to ensure consistent exposure times.
  4. Proper Coating: Ensure that your screens are coated evenly with emulsion. Uneven coating can lead to inconsistent exposure and stencil quality.
  5. Keep Detailed Records: Keep a log of exposure times, emulsion types, and other variables. This can help you identify patterns and troubleshoot issues quickly.

How Lamp Distance Affects Exposure

The relationship between lamp distance and exposure time is important. As lamp distance increases, exposure time increases in proportion to the distance squared. For example, if exposure time is 3 minutes at one meter, then exposure time will be four times that amount (12 minutes) at two meters’ distance and nine times that amount (27 minutes) at three meters.

To determine adjustments in exposure time when proper exposure time and lamp distance are known quantities, this is the formula: Old Exposure Time x New Distance²/Old Distance² = New Exposure Time

how lamp distance affects exposure for screen printing

Contact Chromaline Today

By following these steps, you can ensure that your screens are exposed properly, leading to better prints and a more efficient screen printing process. Proper exposure not only saves time but also enhances the quality of your final product, giving you professional and consistent results every time. If you have any further questions about how to use Chromaline's Dual Exposure Calculator to determine proper exposure, or about any of our Chromaline screen printing products, please contact us today.