Step Test to Determine Proper Exposure Times

Creating an Exposure Step Test: How to maximize Murakami Emulsions

Proper emulsion exposure is crucial to your bottom line. Nothing is more costly than having a press stop during production. Quite often the problem can be traced back to poorly exposed screens that exhibit pinholes, stencil breakdown, or poor quality prints that will affect production yields. The cross section of a screen below shows the dramatic loss of emulsion on the squeegee side of the screen. During development precious microns of protective emulsion are washed off leaving the screen susceptible to pinholes and breakdown. Correct Exposure Graph Step 1: The Exposure Unit

  1. Use units, not seconds if your exposure system has a built in integrator. Lamps age and lose potency over time. Units measures the amount of light, not time. So if you are using seconds you will be underexposing as the lamp ages and loses strength. Change to units or perform an exposure step test every 2-3 months. You can also use a hardness scale when you shoot to verify emulsion exposure.
  2. How old is the lamp? If you haven’t replaced your lamp in a year or more it needs to be replaced. Your lamp may strike and put out light and expose a screen, but it may lack strong UV wavelengths needed for completely exposed screens. Install a new one and keep the old one as a spare.
  3. What type of Exposure Unit are you Using? The stronger the lamp the better the exposure. Exposure units could be compared to engines, you have a wide range from lawn mower engines to V-8’s. Exposure units likewise have differing strengths (wattage and spectral output.) The step test that follows is designed to fine tune the exposure time needed for your particular exposure unit. Click here to continue reading the article: Step Test Instructions

For more information and specifications on using Murakami products in production please contact our Technical Support Representatives available Monday through Friday 8am to 5pm PST at: (323) 980-0662