Problems with your screen printing emulsion can be especially frustrating: You can’t turn out a good print if you have any problems with your screen’s emulsion or exposure. In a previous blog, we covered some common exposure problems and how to troubleshoot them. If you are still struggling to create, expose and reclaim screens, here are some additional troubleshooting tips to help you address common screen printing issues with your emulsions.
1. Lines or flaws in the emulsion during coating
If lines or imperfections appear in your emulsion as you attempt to coat your screen, take a look at your scoop coater. A dirty scoop coater, or one that has begun to show wear and tear due to use, will interfere with the smooth line created by the edge of the coater, which in turn causes lines or other unevenness in the emulsion as you coat your screen. If this is the case, you likely will see dried emulsion coating the nicks and imperfections in your scoop coater. Often, these imperfections can be smoothed away with a fine piece of sandpaper, but if damage to the scoop coater is too severe, it will need to be replaced.
2. Pieces of emulsion flake off after exposure
When the emulsion overall seems sturdy after exposure, but small pieces wash away during washout or flake off after the screen is prepared, inspect the surface of your emulsion. An uneven coating of emulsion results in uneven exposure. Thicker areas of emulsion won’t cure completely during exposure and will not adhere to the screen completely. If this is the case with your emulsion, you will have to reclaim the screen and start over; it’s nearly impossible to get an effective stencil that will withstand the force of an entire screen printing press run. Before recoating your screen, be sure that the screen mesh tension is adequately high, that the frame is sturdy and that your emulsion isn’t so old that the formula is no longer smooth; all of these factors can result in an uneven application of screen printing emulsion.
For more information on maintaining your screens, check out Proper Mesh Care: How to Maximize the Life of Your Screen Printing Screens
3. Loss of fine detail during screen exposure
Loss of detail in your screen printing stencil can be frustrating on press, but it can be even more frustrating when you can’t get your screen to expose and washout with the detail of your art positive in the first place. Make sure that your positive is opaque enough to block all light, and make sure that your positive is making thorough contact with the glass in your exposure unit so that no UV light is finding its way under your image. An over-exposed screen can cause you to lose the detail of your stencil, as the fine details won’t easily wash out of the screen. Also be sure that your exposure unit is providing proper lighting: The light source must be bright enough and light coverage needs to be uniform; when stencils aren’t exposing properly or holding adequate detail, an aging bulb in the exposure unit is often to blame.
Looking for some more tips on proper screen exposure? Read How to Expose Screen Printing Screens Like a Pro
4. Screens that are difficult to reclaim
Sometimes, difficulty with screens comes after the printing process, when you go to reclaim your screen. If your screen hasn’t been properly exposed and cared for, it can become extremely difficult to wash away the old emulsion to reclaim your screen. First, always be careful not to let your reclaiming solution dry on your screen. Once the solution is applied, follow the instructions and wash out your screen in a timely manner; if the solution sits on the screen too long, it can ruin the screen permanently. If your screens are constantly difficult to reclaim, you might be allowing your stencils to remain on your screens for too long. You should be reclaiming screens as soon after a print job is complete as possible. Also, make sure that you are using adequate water pressure to force the emulsion out of the screen. Finally, make sure there isn’t any ink lingering in the screen. Dried ink can prevent the washout of emulsion. A dehazing solution can help to remove ink and allow for easier washout.
Learn more about reclaiming your screens here: How to Reclaim Screens for Textile Printing
Great screen prints start with great screens, but there are plenty of common issues that stand in the way of screen printers creating great screens. Knowing how to troubleshoot problems with emulsion coating, exposure, washout and screen reclamation can allow you to deal with those common issues so you can address any problems, create solid screen printing stencils and move on to printing process.