i got a drawing (black) containg several tones of black : 30% , 55% and 65%
my positive is of 70lpi.
what mesh must i use? i have 110, 137 and 175 mesh screens.
i also wondered if having these 3 differents tones of black it's possible to print them on the same screen.
when i take a 175 screen and try to incline my positive to see if i get some "moire", i can see that 55% and 65% blakc is ok but the 30% gets "moire".
any answers? i'm fed up trying to print theses fucking halftones...
Did you make your own film, or at least the art? you may have to change a few things.
For starters, reduce your halftone screen line count to 45 or so, you will have better luck exposing them and holding them on your screen. 70 is pretty fine for graphic printing, it gets harder on textile.
Can you print all 3 shade values in one screen - yes - a photo has these and more all on one.
Your problem with the moire pattern is probably from the 'screen angles', these should all be set the same if you are outputing on one film. sometimes if they are being converted from colour they may have preset different screen angles.
Use the highest mesh count you can to acheive the ink lay you need - the coarser meshes for black shirts with white ink, the higher meshes on white shirts with colour or black ink.
Use an eliptical halftone dot...better still use random or stochastic...
way easier to print on textile and other screenprinting applications than gridded halftones, way less opportunity for moire, way easy to expose, control, etc.
A rough rule of thumb to determine halftone/mesh count is 3.5 or higher...
so a 45 line screen should have a minimum mesh of 157.5 or more. the higher the count, the easier to hold the detail.
You need a good stencil material, a good positive, a tight screen, a sharp squeegee, halftone ink (not always, but it helps) and a consistant print set up if you are going to print nice halftones.
I'm printing 40 & 30% black screen tints with 50 line screen today. I'm going to try 230 mesh if that doesn't look good to me or if I start smearing out the dots I'll go to 305 mesh. I'm going to use newman roller frame.
The tension will be at 35 newtons (the amount of tension of of screen)
I will be using Rutland process black ink.
I'll try taking a picture and then PM you so maybe I can show you the results.