Can you Explain That Again?

April 6, 2009

Still wondering what all these screen printers are talking about? Well, here are some more terms, in plain speak, to keep you in step with the screen print pros!

Flooding The Screen: This is a single stroke of the squeegee that is done with the screen in a floodingraised position. Holding the screen up and off the print surface, grab most of the ink and lightly push it to the other side of the screen. Your goal here is to spread the ink over the entire surface of the open areas of the image but not push it through. You do this so that the print areas will not dry out by being left open while you switch out your paper or t-shirt and that the entire open print area has ink that is ready to be pushed through on the print stroke. The flood stroke is often done when printing paper and when printing t-shirts and signs but it’s not often done for fabric printing.

A Strike-Off: Instead of a flood stroke fabric printers often do a first strike-off. This is a regular print of four passes on a scrap or testing piece of fabric. You would do a strike off on your scrap fabric then move your screen to your first registration point on your good printing fabric and begin printing. For whatever reason, sometimes a completely dry screen won’t let the ink pass through nicely on the first try, so a strike off somewhere other than your actual print surface can get the screen primed for the first print.

Printing Pass: This is one stroke of the squeegee from one side of the screen to the other. In paper printing you often do one flood stoke and one print stroke, or pass of the squeegee (some may do up to three passes of the squeegee but that depends on your print surface). In fabric printing four passes are standard. Keep the number of passes you do for each print consistent, a variation of even a single pass can change the colour of the print just by adding a bit more ink to it.

Registration Mark: When doing your registraion you will want to use a registraion mark to measure from.p1010218This is a point (often a circle with an x in it) that is on the exact same place on each of the film positives for each of the colours in your design. If the film positives were layed one on top of the other so that the lines of the image line up as they should, the registration marks should be one on top of the other seamlessly.

Registration: This is a term that refers to how the different colours in a print are lined up together. If you have a design that has four colours in it you will need four screens and each of these screens will have to match up with one another when they are printed. Registration is how you make sure that is done properly. 

Ben-Day Dots: The Ben-day Dots printing process, named after illustrator and printer Benjamin Day, is nike-lichtenstien-vandal-2when a series of small colored dots which are closely-spaced, widely-spaced or overlapping are used to create an optical illusion of grades of colours. Magenta dots, for example, are widely-spaced to create pink. 1950s and 1960s pulp comic books used Benday dots in the four process colors (cyan, magenta, yellow and black) to inexpensively create shading and secondary colors such as green, purple, orange and flesh tones. Ben-day dots differ from halftone dots in that the Ben-day dots are always of equal size and distribution in a specific area. 

 

Halftone pattern: The halftone pattern is used extensively in sign making because it can be used

detail-viewto replicate a full spectrum of colour from a distance by only using four screens and the process colours (cyan, magenta, yellow and black). It simulates this continuous tone imagery through the use of dots, varying either in size or in spacing or in shape. This basic optical illusion makes the dots appear as smooth tones when seen at a distance. The semi-opaque property of the ink allows the halftone dots of different colors to create other colours when layered one on top of the other.

Single colour jobs use a screen angle of 45 degrees for halftoned images and colour tints . The 45 degree angle is the least noticeable and offensive to the human eye whereas an angle of 90 degrees is very obvious and draws attention to the dots rather than the image detail.

Direct and Indirect Stencils:  Simply put, an indirect stencil is one that is not permanently (or semi-permanently) attached to the print screen. This could be a piece paper that is taped or adhesive spayed onto the screen or found objects that have been layed over the print surface and screen printed over top of them. They still act as temporary resist to the ink but as soon as you wash the screen or lift it away the stencil is no longer usable. A direct stencil on the other hand is one that has been chemically attached to the screen mesh so that even it it’s moved or washed it will remain, at least until you purposly strip it way.

Stripper: This is screen stripper not your friendly neighborhood pole dancer. Screen stripper is a chemical (a p1010519mild acid) that is diluted and sprayed onto a screen with emulsion to help remove the emulsion so the screen can be reused. Most screen strippers are diluted in a 20 parts water to one part stripper. You will spray your screen with water on both sides, then spray on your stripper and scrub with a nylon bristle brush. Use goggles and a a vapor mask while you do this. DON’T leave the stripper on for more more than 30 seconds or your emulsion will become permanent! After the 30 seconds have elapsed then take a pressure washer and spray off the emulsion.

 

Have you got more questions about screen print terminology? Leave your comments and let me know what your wondering about. 

Happy printing!

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