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Screen Printing Cleaning: Pressure Washing in the Printing Industry |
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One industry that has embraced power washers to improve employee safety is the printing industry. Different inks are applied to a wide array of substrates that range from textiles to plastic, wood and metal components of some larger items. Originally, workers apply solvents when removing inks, haze and emulsions to reclaim screens. They also engaged in forceful scrubbing in a washout area. This posed possible exposure through skin absorption and inhalation of the cleaning chemicals. Among the chemicals that are commonly used in screen printing cleaning include methyl ethyl ketone, terpenes, mineral spirits, xylene, heptane, toluene, hexane and glycol ethers. These are mainly volatile organic compounds that can pollute the air and many of which are toxic. Mineral spirits comprised traces of toluene, xylene and benzene while hexane has been associated with peripheral neuropathy. Because of the potential health risks associated with screen printing cleaning using chemicals, some screen printing companies have developed a high pressure screen reclamation process which greatly minimized the use of chemicals by using pressure. Wastewater treatment and chemical exposure were also reduced. |
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Current Screen Printing Cleaning Practice Screen printing cleaning process involves four steps and these are ink cleanup, removal of emulsion or stencil, dehazing and degreasing. Generally, using higher pressure means (1) much cleaner screens; (2) less labor time used; (3) less usage of chemicals. A total maximum amount that has been seen on the gauge is around 3,000 psi and 2,500 psi on the nozzle. Some people who do screen printing cleaning claim that pressure greater than 1,500 psi will do screen damage, but that is not precise. If the screens have flaws, any pressure can damage it. Of course, using the pressure washer or the sprayer wand improperly can cause damage. Ordinarily, large screens take time to clean and this is why some large format shops often purchase a large, high-volume pump system with a nozzle pressure of 1,250 psi or higher. Most washout booths come with some kind of angled support shelf for silk screens. Many washout booths also have back lights. Large format screen printers usually have stainless sinks or even complete rooms that have floor drainage that surrounds a central area that is used for suspending screens or leaning screens against supports so that pressure washing can be performed in a complete 360 degree sweep without lifting and moving the large frames. Safety is also important when doing any kind of pressure washing, to get tips and accessories check out our power washer safety tips. The same four chemical work phases are common with all types of ink, but the required chemistry for every ink system is specific. In most cases, the frame is usually placed in a dip tank for around 20 minutes. The time in tank varies depending on the strength of the chemical. Organic solvents are usually used for dissolving ink and a specialized chemical solution, typically a low strength acid solution, is used during the emulsion removal part of the screen printing cleaning process. |
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Virtually no stencil removers are capable of giving good results without the use of a pressure washer that will blast away all the loosened emulsion. A caustic-soda solution with moderate strength mixed with a light solvent is generally used in removing haze. Dehazing is not something that is automatically done each time a screen is reclaimed. The last phase of screen printing cleaning is degreasing. In some cases, degreasing is usually not necessary after screen dehazing as most dehazers are capable of eliminating oils from the mesh. |
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The publisher of these pages is in no way responsible for any damage caused to you, your pressure washer, anyone else, your property, or anyone else's property by trying to implement or by successfully implementing the above-mentioned performance and services. Read Related Articles:
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