Screen printing is a very old printing process where an ink is applied directly onto the substrate through a plate/mesh. This mesh is stretched on a frame. This plate will therefore have a sealed image in the body that will be the one that will reproduce our design. This only allows the ink to pass through the sealed area and the rest is not printed.
Having a plate with a design created for each ink makes the printing system very repetitive. Hundreds and thousands of prints can be made without losing quality. This makes it a simple and above all inexpensive type of printing.
The most common uses for screen printing are in merchandising products and especially in textile products. The use of t-shirts with this type of printing stands out.
Making the mesh/plate:
The first thing to do is to prepare the frame with the mesh so that the design can then be printed on the product.
Once the mesh/plate is well placed in the frame to be able to engrave it, it must be cleaned with water to eliminate possible impurities.
When we have the design already selected we must print a negative. With the help of a photosensitive printer, we adjust the negative in the zone that we want of the plate and it is inserted inside the printer. With the help of the printer, we close it well and proceed to the vacuum adjustment so that no air enters. So the printer is started up and with the projection of the light on the frame, having the negative well placed that will leave the design on the plate.
It is washed again well with water under pressure to be able to release the mark that has left the photosensitive printer. Already we will have ready frame with the captured negative.
It is necessary to bear in mind that for each ink that is wanted to be captured in the impression a different plate must be used, that is to say a plate by ink.
In this type of printing, when the application is made by a single ink. In the case of having a design with several colors, as many plates are made as colors we have in the design.
Application on textile support
In order to be able to print on textile material, the most common are t-shirts, we will need a screen printing machine with several bodies. Each body contains a mechanism to be able to attach our frame at the top and to be able to flex it down to use the technique. In the lower part, at hip height, there are the boards where we can place our textile support and print on it.
There are single body, two body, 4 body and even 6 body machines to make the printing technique in several colors faster and more efficient.
The first thing to do is to adjust the frame to the upper support of one of the bodies so that it is perfectly aligned and does not move one iota in the print. Once adjusted, it is bent downwards so that, using some marks on the lower board, the frame can be well aligned for a square print.
Keep in mind that both the frame at the top and the bottom board must be adjusted perfectly and kept rigid so as not to get problems in the subsequent process.
The next step is to put in this case the T-shirt tightly fitted on the bottom board for further marking. Once ready, the frame is flexed to a horizontal position without letting it fall to the area of the board.
It is at this point that the ink is applied on top of the frame/mesh to mark it on the T-shirt. A respectable amount of ink is applied for the size of the logo, since it can be removed without problems and used again. When the ink is ready and the rubber rake is placed on top of it, it should be flexed all the way down, making our plate touch the t-shirt.
It is just at that moment when, with the frame already fixed on the board, the rubber rake will be passed firmly and pressing inwards to allow the ink to pass in our area marked by the plate.
When the ink has passed to the other end of the plate, the frame is released upwards and the silkscreen will be printed in that ink on the T-shirt.
MORE THAN ONE INK IN THE PRINTING
In cases where the design to be printed has more than one color, as many plates will be made as there are colors in the design.
Let’s take the example that the design to be printed has 3 different colors, black, red and yellow. A plate will be made with only the part of the design where the black color will be, another where the red color will be and another where the yellow color will be.
In these cases, it is very important to properly align the upper support where the frame is placed with the board where the support to be printed is placed. In this way, when each of the inks is placed, they will match.
So once all the frames have been created, let’s suppose we have a 4 body machine, we will place each frame on each of the supports we have (one will be left over). So they are correctly aligned using marks that we can put and the same printing method is done one by one.