Screen Printing Process - 17.03.23
For this process, you will need to have a black-and-white design or convert an image into a bitmapped image in photoshop. The bitmapped image will create areas that are easier for the ink to get through and will also be easier to see the image.
To bitmap an image, first change the image into a black and white image, then you can adjust the contrast and levels so that it can be a high contrast image. After this has been done, the layers in photoshop must be merged and then bit-mapped by going to modes -> bitmap, which you can then select the amount of bit mapping being used. For this, difference diffusion is fine, but for more colour prints, a half-tone must be used.
After this has been done, it must be printed through a good printer in black and white. A good printer must be used as banding from the printer will occur and can damage the look of the print later. After printing onto paper, oil is used to wipe the printed paper so that the paper can shine light through it. The blacks will absorb light whilst the white will allow the uv light to shine through.
After this is done, a screen print emulsion is applied onto a screen and dried for about 5 minutes. This can be done before prepping the oiled paper to save time. After the emulsion has dried, the dried screen is then placed onto the UV exposure unit on top of the oiled paper so that the light is exposed to the screen.
The screen must have the hole side up, with the oiled paper underneath so that light can then pass through the oiled paper to cure the UV-sensitive emulsion. A piece of wire/string is then placed on top to ensure that there is not a tight vacuum.
After this, the machine is turned on, the top of the machine clamped shut (to prevent UV exposure and to form a nice seal) and then the vacuum pump is turned on. A timer on the machine is then set so that we will just need to wait for it to be done. The timer can accurately time exposure as the hotter the blub, the less time is needed for exposure. UV Light emitted through the glass hardens the emulsion on the screen to create a negative and thus can be used to print onto paper and others things.
The unhardened emulsion that was used in the process must then be washed off to reveal the areas that the ink will not penetrate and soak into the medium underneath. After it has been pressure washed and cleaned with water, it can go back to dry in the drying cabinet for about 10 mins, depending on how big the screen is used.
To create your own inks for the screen printing process, it must be mixed with white pigment as it is cheaper to get a batch of white pigment, rather than getting individual ones (we are only printing in low volumes).
Mix in a small amount of the coloured pigments in a tub of white taken from the bigger tub. You can test this to see if the pigment is still clear or slightly white on a piece of scrap paper.
After this, you can prep the screen by propping it up slightly (using a roll of masking tape or some other one) and then using a squared-edged squeegee and a generous amount of ink, squeeze the ink through the screen. This can now be placed (without moving it) onto paper or your medium of choice and squeeze the ink through the screen once again.
If multiple prints are going to be made, you must be quick to apply the ink or the ink will have dried up and blocked the screen.
Below is the screen print outcomes that were made for unit 3, which can be found by clicking the link.
For this screen print, I used 3 different screens to create this trichromatic colour as images are usually in either RGB or CMYK colour space. RGB for Red, Green and Blue (which is optimsisedd for screen viewing) whilst CMYK is Cyan, Magenta, Yellow and Black and is used for prints. K is also called Key due to it being key for prints to look the fullest.
The first screen was Cyan, which was the first layer, Magenta which was the second and yellow being the third. I liked the way that the layers aren't together properly, which was the outcome of the screens not being aligned properly and without anything to align them with. I also chose an outcome with black and white photo with a 3D anaglyph, which turned out to not function properly, but was still able to produce some of the effect, just not as good as it would be on screen or through a proper printer, as the resualution of the bit mapping is not high enough to enable screen printing as an option.