screen printing > Waterbase and Discharge
Discharge buildup on underside of screens
cclaud3:
Still dealing with buildup/sticking that eventually cuts out the image on the later screens in the print order.
Flashing between colors is the only way to get through the print.
I've been told that it is common to print 5-7 colors wet-on-wet. We have trouble with 2 colors. Trying to space 2 colors before both flashes then having 2 colors after 2nd flash for a 6 color print is difficult.
We are using Matsui & Aquarius sytems.
Screen room humidity sits between 35-40%. Averaged between de-humidifier and separate hydrometer.
Production warehouse is around 50%. Outside of building we're about 85% RH.
Softener rubbed on bottom of screen only gets us so far.
Of course trying to run dark/low white base mixes first.
150s, 225s, 280T meshes all produce buildup. Coated 1/1 on sharp.
Squeegees 60/90/60, 70/90/70, 80 duro used. 80 certainly produces the least buildup but hard to get full saturation.
Very hard to medium pressures used.
5-15 degree settings on ROQ attempted.
1 & 2 stokes attempted.
We have tried to forgo the flashes but it's a disaster of sticking/lifting up.
Household moisture meter on Chromaline WR shows 0% moisture on ready-to-print screens & coated/dried screens. This is surprising with the 50% production area humidity.
SAATI PHU Hr shows 7-8% moisture. From research 4% or lower is the target.
The manufactures/sellers of the product don't know what the problem is. I have been told to add pressure and no-one else is experiencing this.
The aquarius system has plenty of colors calling for white discharge base with the clear. There's only one white DC product so I don't see how to get around using the full white discharge in the base. There is also white pigment from the bottles in the colors.
Aquarius has youtube videos of 3 colors printed without flashing using 1 stroke. That is impossible for us.
Other suggestions given to us is to use a softener/water mix misted over ink.
Fogger system
Told our humidity is too high but to add moisture to the ink while printing.
My best guess is that the screens are retaining moisture that is causing the ink to stick to the backs of the screens. 0% moisture reading rejects this idea? I am considering an industrial dehumidifier for the entire production area that would be $1200-2000.
Using a SAATI LED, with no screen breakdown. 3 Minute exposures show good on stouffer strip and clean rinse-outs. So my guess is either moisture in screen from ambient humidity or not fully baked screen? No break downs though.
Steve12Lowry:
Try using the softbase formula and swap the base out for the discharge base. See how the color compares to the original discharge formula.
cclaud3:
Thanks I will try that. Forgot to mention that we ran a 4 color. Black, softbase, discharge green, discharge white. The softbase (it was a darker/medium brown pantone) stuck just the same as the black & discharge green. Sent pics to regional rep. Avient says this is unheard of.
It's got to be the humidity.
tonypep:
Traveling now but quick tips.......penetrant and retarder additives I use a combo. This usually fixes this however do not exceed 10% in either ratio. I will add further but it will take a few days
Steve12Lowry:
--- Quote from: cclaud3 on June 30, 2021, 05:12:57 PM ---Thanks I will try that. Forgot to mention that we ran a 4 color. Black, softbase, discharge green, discharge white. The softbase (it was a darker/medium brown pantone) stuck just the same as the black & discharge green. Sent pics to regional rep. Avient says this is unheard of.
It's got to be the humidity.
--- End quote ---
Very surprised to see the softbase causing a lot of buildup. Single or double stroke? Are you using thin thread mesh?
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