![]() The step wedge test works by taking a time where a screen is sure to be underexposed and exposing it in increments of your choice until it is overexposed. While not perfect, step wedges are a manual method that can help gauge exposure time-assuming your stencil is perfectly opaque. While overexposed screens can disrupt the screen printing process, they can be largely avoided. If this is not done properly, or if the image isn’t pressed firmly enough against the glass, this may also cause the image to not wash out properly. Part of traditional screen printing setups include using a vacuum to remove air from in between your positives and your emulsified screen. ![]() Not only are these older, worn screens more prone to fogging, but they’re also more sensitive to changes in storage conditions. Older screens that have been left coated and unused for long stretches of time will be more difficult to expose. For instance, if your coated screen is not stored properly, it can become foggy and leave patches on your image after printing. Overexposure is the most common cause of a stencil not washing out, but it is not the only one. Other Reasons an Exposed Screen Won’t Wash Out In fact, if large parts of the screen are overexposed, it may just be cheaper and faster to scrap the screen and start over right away instead of trying to rinse it. If this happens, then you’ll be unable to do anything except remake the screen and start over. Whether you opt for bleach or an emulsion remover, letting either dry completely will chemically “lock-in” the emulsion. The process is similar for both products: Apply the emulsion remover to the screen on both sides, and let it sit for about 45-60 seconds before scrubbing thoroughly and washing it out. While using more water may not wash out an overexposed screen, sometimes a screen can be cleaned/reclaimed with bleach (the stronger, hardware or pool bleach, not laundry bleach) or, preferably, an emulsion remover. However, doing this can result in either the screen being broken or your print’s quality and detail being ruined. At first, you may be tempted to use more water or higher water pressure to wash out the screen. The most common and easily detectable sign of overexposure can be seen when the exposed screen won’t wash out, but other signs of an overexposed screen could include significant loss of detail and degraded edges on the print.Īn overexposed screen is incredibly difficult to wash out, and nearly impossible in some cases. Additionally, if your film positive s or CTS inks are not opaque enough, too much light will come through during exposure, leading to overexposure. The type of emulsion being used, the exposure unit, and how much emulsion is applied to the screen are a handful of factors of which to be aware. Exposure time can vary greatly depending on several factors. Overexposed emulsions are essentially “cooked” and will not easily come free of the stencil. Another primary cause is too much UV light. One of the primary causes of overexposure is, as you might guess, too long of an exposure time. ![]() More importantly, we will cover how to avoid it in the future. To mitigate this, we’re going to cover what to do when an exposed screen won’t wash out. Overexposure can make it so that your exposed screen won’t wash out. Overexposed screens are more straightforward but still far from ideal. Underexposed screens cause a long list of problems, making it difficult to determine what exactly the issue is, and its cause. Even the most seasoned screen printers will occasionally have to deal with improperly exposed screens.
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