Screen printing is a versatile and widely used technique for transferring designs onto various surfaces, but it's not without its challenges. If you've been struggling with screens that won't wash out properly, you're not alone. In this tech overview, we'll delve into a conversation between experienced screen printers and explore the possible causes and solutions to this frustrating issue. Whether you're a seasoned screen printer or a backyard enthusiast, this guide aims to help you diagnose and resolve the problem.

Screen Printing Basics

Before we dive into the troubleshooting process, let's briefly review some key concepts:

1. Emulsion: Emulsion is a light-sensitive coating applied to the screen. It hardens when exposed to light and water-resistant, except in areas where it's washed out during the screen preparation process.
2. Exposure Unit: This device emits UV light to expose the emulsion-coated screen with your design, creating a stencil for ink to pass through during printing.

Problem: Screens Won't Wash Out

Symptoms: After exposing screens, you notice that the emulsion won't wash out entirely, leaving a faint image on the screen that won't budge.

Possible Causes and Solutions:

1. Inadequate Artwork Opacity

Cause: If your design isn't opaque enough to block UV light during exposure, the emulsion won't wash out properly.

Solution: Ensure you're using a film positive that offers sufficient opacity. Avoid using low-quality office supply films, and consider using a more ink-receptive media type when printing with inkjet printers.

2. Overexposure

Cause: Overexposure to UV light can lead to emulsion hardening, making it challenging to wash out the screen.

Solution: Experiment with shorter exposure times. Create a test screen with a range of exposure times to determine the optimal duration for your setup.

3. Emulsion Quality and Type

Cause: Using an ultra-fast emulsion like ULANO ORANGE can decrease your exposure latitude and lead to overexposure.

Solution: Consider switching to a different emulsion with more forgiving exposure characteristics for your specific setup.

4. Improper Drying Conditions

Cause: Screens may pick up UV light during drying, leading to premature exposure.

Solution: Try coating and drying a screen without exposing it to light. If the emulsion hardens during this process, it's an indication that UV light exposure during drying is the issue. Adjust your drying setup accordingly.

5. Light Source and Exposure Unit

Cause: The proximity of the exposure unit's light source, in this case, fluorescent tubes, can lead to overexposure.

Solution: Experiment with a broad range of exposure times. If your unit uses fluorescent tubes, exposure times may be measured in minutes rather than seconds.

Screen printing issues like screens that won't wash out can be frustrating but are solvable with systematic troubleshooting. Consider the factors mentioned above, and adjust your process accordingly. Remember that every setup is unique, so it may take some trial and error to find the perfect settings for your specific equipment.

If you're a backyard printer like the last person in the conversation, don't be discouraged if your process differs from others. Success is what matters most in screen printing, and as long as your method produces the desired results, you're on the right track.

For more tips and in-depth guides on screen printing and other tech-related topics, don't forget to follow our YouTube Channel, explore our Tech blog, or visit us locally in Greensboro, North Carolina, for hands-on assistance and expertise. Happy printing!