Tension and Discharge/WB (Tony?)

[Gilligan]

So I've read over and over by people I absolutely believe and trust, that you don't really need high tension for WB or Discharge.

I do understand the principle as you aren't trying to just kiss the ink to the shirt and shear off the ink at that point, you have to DRIVE the ink/chemical into the shirt for it to be effective.

Where I think things get muddy for me is it would seem like registration and such would be an issue... basically all of the problems that low tension cause aren't eliminated by switching to discharge/WB.

So how does it work?  Is it just a happy medium?

Guru's please explain.

[patfinn]

in my opinion, and my old shop all we did was print waterbase all day every day. used all types of mesh statics and newmans
newmans defiantly perform better than statics. Murakami S mesh especially 150s and 225s have a huge open area % also can hold great halftones. having this big open area is great for wb so it doesnt dry in fast and easy also so your getting that good saturation.

after all that you defiantly see a difference in registration. the tension with the open area % allow you to not have to drive that mesh to much, and ultimately pull the mesh over the shirt and cause it to come out of reg. basically all the benefits of using newmans with plastisol you get with waterbase.

when you add the right amount of water and retarder and stay on top of it throughout the run, you can get that saturation your looking for without forcing it into the shirt.

[ZooCity]

We just keep all of our S-mesh (literally all we print with for the last 2 years, for both plastisol, wb and most flatstock) at recommended tension which averages around 24n, not far above the "danger zone" of low tension although some, like the 180/48 are happy as high as 32n.

I don't think low tension is ever good but thin thread, high open area meshes do tend to run at low-er tension as the industry hasn't advanced far enough in mesh thread construction to allow the thin threads to hold up to the brutality of higher tensions...or maybe we're all just too cheap to pay for it, hard telling.

The reason tension seems like less of an issue with WB printing is that you are printing on contact and it's the heightened o.c. of low-tension frames that causes so much of the issues with them.  It's not really about tension, it's about tension opening the door to lower o.c. which increases accuracy all around.  When you are right on the damn substrate it appears as a non issue. 

But, just to toss this out there, you "get away" with more using WB as it has much less gain than plastisol.  I wasn't expecting that when we started and was braced for a lot of wicking but it is minimal.  So minimal, I find butt reg to be an occasional issue on simple spot color jobs as there' just no wiggle room from the gain.  (see thread I just posted on this and spreading/choking) 

The ideal WB screen would be a non existant one featuring massive open area and ultra high tensions on a non-existant, perfectly calibrated machine.  You would print at this whisper thin o.c., getting all the penetration/saturation needed yet enjoying the optimal peel of a ultra high tension screen for very crisp definition. 

Just my rambling thoughts on the matter.

[Gilligan]

Ok, I didn't realize you didn't need Off Contact... but I guess that makes sense, not really going to have pickup or smooshing on previous prints/colors.

I also would have thought WB/DC would be worse with dot gain... interesting information.

[tonypep]

WB and Plastisol both have very different rheolgical and thixotropic characteristics. Think of watercolor paints vs oils and acrylics. All three have very fundamental differences as to their theory of application. Plastisols, while both long and short bodied, are still far denser in composition and require more shear from the mesh. This also causes greater dot gain. Plastisols are nowhere as clear as waterbased inks as they need the required binders and fillers to perform their function; again attributing to dot gain. Obviously ridiculously low tension will eventually cause problems regardless of the ink; such as registration. However I have found it to be less of an issue with WB