ink issues when overprinting with tw inks

[jesusvbarraza]

I started using tw inks about a year ago and i love the inks...but i have some issues when printing one color over another....usually black or dark color on top of a lighter color...the color on top usually has little bubbles or holes, not sure how it happens or why it happens but i don't have this issue with speedball.

any one else experience this or have a solution, my friend joe told me to ask tw about some additive. he said he had gotten something from them, but didn't find it to help. any one else use that stuff?

any help would be useful, I am going to call tw this week and see what they have, but before that I wanted to hear what some printers have to say.

thanks

[crosshair]

I sometimes see this. Usually it's when I've overthinned the overprinting ink. It tends to go away after the first several pulls

[crosshair]

I've also been able to stop it by adjusting flood pressure & squeegee speed (on M&r Saturn)
Don't know why though.

[NeroInferno]

I agree, generally it's caused by over thinned ink. Try to add some fresh ink from the ink can and see the difference. Remember to set a good offcontact for a denser ink.

[Andymac]

Not transferring completely, due to a different surface tension where the other ink is. INk has to 'stick' to whatever it is being printed on. sometimes the viscosity (too thin) or the angle or speed of the squeegee (Crosshair) can affect/correct this.
Sometime you need to treat the surface (corona/flame treatment on some plastics, or wiping with IPA. (not with paper though)
Sometimes you have to go through the whole run and carefully buff with 80 grit before printing your second colour.
Sometime, you just expose the stack to the greatness that is Vancouver Canux and it is miraculously cured and almost prints itself.

[ohdanielsan]

oh man! i have been having this problem with TW inks too! thought i was the only one.

this is the only thing i don't like about their inks. i have literally tried every possible angle/speed/pressure/off-contact and combination thereof. however, i am hand-pulling, so that makes my situation a little more difficult.

i even changed the direction of my pull from long-wise to width-wise, thinking that would do something, but not really.

i personally haven't seen a difference with thinned ink vs. non-thinned ink...in fact, i might even say the thinning helps because the ink can pass more freely through the screen and also fills onto the paper a little easier. i'm also going to say that i feel like it gets worse as the ink dries more, so i have to keep re-wetting or re-inking every 10-20 prints depending on humidity.

the only thing i've been able to do to (somewhat) get around the issue is pull a "dry" pull (i.e. no ink with the squeegee) after the initial pull. but that's time-consuming, and sometimes not possible depending on the image (high detail, small type, halftones, etc).

another thing that i *think* may help, is to mix speedball in there. that's helpful for other things too (slower drying, etc.), but i haven't done enough testing to see if it is 100% effective for this particular issue. i'll keep testing.

in any case, this is a REALLY annoying problem, and if we can get enough complaints about it here in this thread, i will consider bringing it up to the gals at TW HQ to see if there's anything they can do to work with it. i'm past the point of thinking it is something i am personally doing wrong/different, especially now that you guys are having the issue too.

[crosshair]

Assuming we're all talking about the same thing...It's not an issue of the ink not passing through the mesh. If I understand it correctly, it's tiny bubbles in the ink.
This would explain why the problem tends to go away if you just keep going. Also, it would explain why it doesn't happen on un-inked paper, which is porous so capillary action pulls the ink into the tiny voids.
I think there is an 'anti-foaming' additive meant for this.

But I also notice it only happens with inks I've just mixed up. Maybe just mixing ahead of time and letting the ink settle, would fix the issue.

[jesusvbarraza]

i will try changing my squeegee angle, but like ohdanielsan this is the most annoying thing about tw. my friend joe has been printing with tw inks for years and says he has just given up trying to solve the issue, and says that using pre-mixed inks do better than mixing from pigment and base.
The black I use is straight out of the bucket, I was thinking about adding some speedball black or tw pigment and seeing how that works.

[squeegeethree]

It's not just TW inks that do this. All inks can do this. "Wiping with an IPA" seems like a waste of an IPA though.

[dave welker]

If you can plan for it I think its always best to mix inks a day before you print.
Let them sit over night and then give them a stir rather than a shake before you print.