The 21 Step Wedge
The 21 Step Wedge is a valuable tool used in screen printing to visually confirm if the exposure time is properly dialed in during actual production runs. It serves as a quality control check to verify stencils are being fully exposed without under or overexposure.
How It Works
The 21 Step Wedge is a strip of film or transparency containing 21 different densities of gray, ranging from solid black to completely clear. It is placed on the screen alongside the image before exposure.
After exposing the screen and washing out the emulsion, examine the 21 Step Wedge:
- The ideal and properly exposed stencil will show a transition from solid emulsion to clear emulsion at Step 7 on the wedge.
- If the transition occurs before Step 7 (e.g. Step 5), it indicates underexposure – the stencil is not fully exposed.
Using the 21 Step Wedge
- Position the wedge on the screen along with your image before exposure.
- Expose and washout the screen as normal.
- Locate the transition point on the wedge where it goes from solid to clear areas.
- If the transition is at Step 7, the exposure time is properly dialed in.
- If not at Step 7, adjust the exposure time accordingly to hit this ideal transition point.
By using the 21 Step Wedge, you can visually verify during print runs that your exposure times are achieving fully cured, properly exposed stencils for high-quality prints.
Was this helpful?
YesNo
