Learn about good practices for cleaning, inspection and storage of photopolymer plates.
Flexo and letterpress plate surfaces and typographic need to be accurately and safely washed in order to remove the inks (UV, solvent or water-based) used in the process of printing. The whole process requires the implementation of good practices that will extend the service life of polymer matrices, reduce the costs associated with the use of expensive cleaning agents, minimize production downtime and ensure an adequate level of safety for the post press personnel.
Good practices that will help extend the life of the plates and improve the quality and effectiveness of printing.
Clean your plates without delay
Every type of ink used in the printing process begins to dry immediately on plate surfaces. The faster you remove the plates from the printing machine to begin their cleaning, the better the final results.
Fully automatic washing vs manual washing
A fully automated plate washing system is the perfect solution that guarantees exceptional efficiency and safety of the washing process. The end result of this short procedure is a 100% clean and dry plate, ready to be used again. Automation reduces water consumption by up to 30% and detergent consumption by as much as 40%. Staffers operating the machine have no direct contact with chemicals and an additional filtration system allows for multiple uses of the same solution of water and chemical agents. The plate washing machine has been created specifically for cleaning all types of plates and removing all types of printing inks. The machine is very easy to use and takes up very little space.
Very difficult hand washing:
- Pre-rinsing – printing plates should be immediately rinsed with clean water mixed with a mild, specialized chemical agent, such as Quicker Wash UV/Solvent. This will keep the plate surface damp, rinse out main printed areas and limit the number of chemicals needed to clean the plates.
- Washing – the first step is to choose the right detergent for washing photopolymer plates. You should dilute it in accordance with the manufacturer’s instructions for “mild washing” programme. You can spray the plate with the cleaner or wash it by hand. The detergent should generously be applied to the dirty plate. Then, with soft brush nylon or lint-free cloth, we can spread the detergent in order to remove the remaining paint. During cleaning, add fresh detergent directly on the plate and from time to time rinse the printing matrix with water in order to assess cleanliness. You have to be very careful because it is enough to use excessive force to damage the delicate surface of the photopolymer plate.
- Final rinse – after removing all the ink from the plate it should be abundantly rinsed with cold water. The point is to remove any residues of ink or resin. It is also about the precise removal of residues of chemicals used for cleaning. Residues of cleaning agents can speed up the destruction of the plate.
- Drying – the plates should be left until completely dry. Once dry, they should be suitably stored so as to be protected against dust, UV radiation and contamination e.g. with remaining ink.
It must be remembered that it is not allowed to clean photopolymer plates with cheap, low-quality brushes with falling or breaking bristles as they may stick to the surface of the plate affecting ink transfer. You also cannot use metal brushes that scratch, carve and otherwise damage photopolymer plates. Washing with fraying cloths or towels will leave scraps of material on the surface.
For manual washing, use a good quality nylon brush with soft, dense bristles and a special detergent for manual cleaning, e.g. QUICKER Cleaner for washing flexographic plates. It is an odourless, environmentally friendly and safe cleaner that easily removes ink residue and protects the photopolymer surface.
Surface inspection/quality control
Accurate inspection of the photopolymer plate after washing is the key to consistent print quality and reduction of any downtime resulting from the use of dirty or damaged plates. Plate-II-Print HD enables quick inspection of the plate. It allows you to accurately measure dot size on printing matrices and detect even the slightest impurities. It is worth exploring a huge potential of this small, portable and easy-to-use device in resolving current problems with the printing quality. Plate-II-Print HD is designed to work with all types of flexo plates available on the market.
After each printing run, the plates need to be washed as soon as possible and then placed in storage. It is especially important to avoid exposing the plates to daylight or UV light, which can result in the loss of physical properties. Plates should be protected from light by being stored in special drawers or dark bags. Do not stack the plates directly one on top of another. You can use separator sheets but the height of plates stacked in this way should not exceed 15 centimetres. You should always follow the manufacturer’s requirements for appropriate plate storage. Temperature and humidity are key parameters that should be subject to permanent control. Excessively high temperature can make the plates sticky and unsuitable for reuse. Similarly, excessively high or excessively low humidity has an adverse effect on photopolymer matrices. Storing plates on cylinders or in a curved position increases their surface tension and significantly reduces their resistance to external factors.
Keep in mind! Proper plate washing and storage have a direct impact on plate life and on production quality and costs.