I am having a sawtooth/stairstep edge problem that I just can't figure out. I have searched this forum and the internet and I am not finding a definitive answer.
Here is my situation. I am just doing fairly simple one color designs. I am using 110 white mesh screens. The last few screens I exposed with ChromaBlue emulsion, but I have tried Ulano QTX and had the same results. I am exposing my screen with a home setup, one 500W halogen above my screen with a piece of glass on top of my film positive that is taped to the shirt side of the screen and a piece of foam covered in black fabric on the squeegee side. I am creating my artwork in Illustrator and printing onto inkjet film positives with an Epson 1100. The sawtoothing is most noticeable on the straight edges of my designs. Also, when I use International Coatings Matte Black ink the jagged edges are much more profound than when I use Union Maxopake ink.
You can have beautiful films, but a 110 screen is going to give you sawtooth unless you have some super trick emulsion or cappilex emulsion film to create a a built up edge of emulsion below the mesh. Regular coating on 110 or any course mesh will sawtooth everytime, because the opening in the mesh are large enough and visible to the naked eye. ONe way to eliminate sawtooth is to increase your mesh count - the finer, the smaller the opening squarers, the less visible to the naked eye. You can still see sawtooth on a 350 mesh - but you need a magnifying glass/loupe. It is the defining characteristic of screenprinting, and differentiates a print from other process.
the suggestion above to increase your stencil thickness will help if you are stuck on using 110 foe whatever reason. Dry the screens with the bottom side down. You can then recoat the screen bottom after the first coating has died, this thickens the emulsion, and gives you that dropped stencil edge below the mesh, which if you do it right, will bridge the openings in the mesh. Like cappilex, but done with direct emulsion.
With a thicker emulsion coating, you need to expose longer, to make sure it hardens all the way through. And the emulsion needs to be high resolution, usually a dual cure or strait SBQ/one pot, so it gives that sharp edge.
Yeah, this too. If you are making films with low output resolution on your printer, you get the same effect, sawtooth/pixels, but mostly on curves. the fact it is on straight lines in the print, and you are using 110 mesh, suggests mesh is the culprit.