Question about moire?

[Ripcord]

I dunno...Maybe it's just me, but I don't get that shiny thick coated look on older mesh, no matter how many strokes I give it. (Still prints fine, it just doesn't "glisten" the same as when it was brand new.)

[jsheridan]

I don't get that shiny thick coated look on older mesh, no matter how many strokes I give it

round or sharp edge?

[GaryG]

If the EOM is enough it will glean, regardless of age or amount of abrasion of mesh.
It's as simple as light reflecting off the emulsion I would think.

[Frog]

If the EOM is enough it will glean, regardless of age or amount of abrasion of mesh.
It's as simple as light reflecting off the emulsion I would think.

Exactly. I'm fiiguring that Rip doesn't have as much emulsion there as he may think.
I find that with most of my screens (125-230) my high solids emulsions, and my technique, it's usually two passes with the round edge substrate side, observe the glisten on the squeegee side, then the one pass on the squeegee to push it back to where it does its job.

[mimosatexas]

For me, using S-mesh, glisten on basically any mesh count but 300 is 2 on shirt side, then i follow with one on the squeegee side.  That is with the Monster Max coater, which is kind of a middle ground between the standard round and sharp sides of other brands.  For regular mesh it can depend a bit based on the age of the mesh and the meshcount, typically requiring more strokes for higher/older mesh.  I use additional squeegee side strokes on lower meshes though to increase eom typically.

As to the issue of not achieving glisten, or having irregular glisten, I used to get this too, but it was due to having less than optimal reclaiming processes.  If you have old emulsion/ink, etc in your screen it can cause this problem.  It may not be visible, and it may even print fine most of the time, but not seeing the glisten is probably a result of the mesh needing a deeper cleaning due to having a slow buildup of residual emulsion and ink.  I would look into any number of the products advertized as dehaze or ghost removers.  There are a huge range of strengths when it comes to these, from some you can just scrub on and wash off during your normal process, to some you need to wear protective gloves/mask/apron and card on carefully.

[Gilligan]

What chems are you using these days Mimosa?

[markdhl]

Screen Print Dan,

Distance of the print head back on the wax jet can also make a big difference in halftone as well as other adjustments.

Contact me direct anytime for more information
Mark Diehl
Douthitt
mdhlexp@aol.com
313 515 8635

[Screen Dan]

Hey Mark, great to see you on here.  Haven't spoken to you in a month or two.  Everything is working great, as usual.

I'm aware...we never have any issues with moire anymore, but, if we ever do a high line screen job we always bring the print head as close as we can.

I do have another question for you though, so expect an email any second now.

[ABuffington]

Angles to avoid moire are ball park only.  The reason is how was the mesh was captured relative to the frame?  If the mesh is angled 2-5 degrees to the frame it will change the angle needed in the image output.  How the mesh was stretched is another area.  Bar stretchers with poor capture technique can distort the mesh and cause moire, or spot moire within the print to develop.  As John mentioned, ellipitcal dot shapes can help, but I have many printers who use round as well.  It can take some trial and error to find your shop's recipe. 

One tool you need to make:  Takes awhile but you can use this file over and over to check mesh for moire.  Create a 0-100% gradient, convert to bitmap and assign an angle in Photoshop and then assembling 90 seperate bitmaps with 1-90 degree angles helps see what angles work.  We use a file size of 1.5x3 inches for a 23x31. Yeah this is a lot of work and bitmaps have different dot shapes, but placing the film square on the frame and mesh can show interference patterns develop.  Shooting this film or image and printing it also reveals what comes close in terms of angle.  But if you stretch screens yourself, or capture mesh in Newmans it is easy to get the threads off by a couple of degrees as well and affect the correct angle.  Stretch 10 300's and a couple will moire and the others may not.  The art is also key.  Put a 12x16 inch 0-100% gradient in the art and you are asking for banding or some stripes to occur.  Use art with shorter tonal spans and busier art and the exact same angle and line count may not show any moire at all.  Large vector designs are prone to finding the one halftone percentage that does moire.  So for 150/48, 45 and 55 lpi tonals are better with busy art, smaller details.  If you need large vector gradients use the 4.5x halftone line count for the mesh count, or move up to 225/S.