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]

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.

Very surprised to see the softbase causing a lot of buildup. Single or double stroke? Are you using thin thread mesh?

[cclaud3]

Yes 150s & 225s. single stroke for that job as it was one of the first with the system to try to follow the TDS. 400+ pieces and sticking happened around 50 pieces in.

[Raw Paw]

I may have overlooked this in your thread, but if you aren't using retarder I would highly recommend it.  We add 4% in every ink mix, and for discharge white we use 4% retarder + 4% water

[cclaud3]

Ok, just updating this from the last 6 months of printing.

We print water based all day on a 10/14 automatic.

Magna discharge is the only series that doesn't buildup for us. I'm not sure what the difference is chemically but every time we try to sneak a matsui or aquarius dc color back into a multiple color print it builds up and start blotting out the subsequent screens. Matsui spot black non-dc also builds up. Magna black made from either HB or ND Xtra base prints great without buildup. We are not using any additives with the magna although we did purchase some retarder initially for the Edge series which we were not fans of.

Magna dc allows for a large amount of colors wet on wet for as many prints as we want. We still use Matsui if we are unable to color match to an older multi-color print that it was used for or sometimes just for a 1 color print since we have so much of it.

Over the last couple of years we have used many different emulsions. All brands & models resulted in the same buildup with the other ink lines. The magna works with the last few we've used.

[Admiral]

I think Matsui is what I have used in the past for colors, don't they have a brite base and high mesh base? the brite base made the inks stick, the high mesh made it so we printed WOW without flashing, 8-10 screens just fine.

For emulsion I have always used SP-1400 for water based discharge printing, others we have had issues with. YMMV but that's what I recall, we print like 1 water based job every 4-6 months now.

[cclaud3]

We have nearly every discharge base that they make.
Brite White & Clear, Brite White, Super 75 White, Binder 301, High Mesh (HM) White & Clear. We didn't fool with the first down/ub product.
With and without Quick additive. Buying everything in 5's.

High mesh was too dull and still built-up on backs of screens. Apparently something in our environment didn't like the Matsui & Aquarius dc line for wet on wet.

SP-1400 was tried. We have a moisture meter that implied dry screens, along with a few other tests. Following all the standard protocols for water based efficacy.

Just throwing this update up for the others that experience(d) the same issue. Thanks