Wet on Wet questions

[Gilligan]

I've done wet on wet but it was extremely basic flat art with nothing touching.  Even still off contact, low tension and improperly tuned press caused issues.

So now I'm looking at doing some "real" printing... So my question is what about traps and such... If I'm "overlapping" colors what is the concern with contamination?  Or should I just flash given that I'm manually printing?

For an example this tutorial on separations is what got me thinking about it.
http://www.smashingmagazine.com/2010/12/07/preparing-artwork-for-screen-printing-in-adobe-illustrator/

Stop 8 and 9 have some orange and red printing on each other... they aren't talking about production only preproduction so it leaves that whole topic up in the air.

[hazeremover]

So now I'm looking at doing some "real" printing... So my question is what about traps and such... If I'm "overlapping" colors what is the concern with contamination?  Or should I just flash given that I'm manually printing?

Unless you're goal is to achieve an third color as a result from intentionally overlapping wet inks, there is no need to trap solid spot colors. Butt register, or knockout, of  the inks (artwork) will yield the best result. Of course there are exceptions depending on the artwork, halftone blending, black trapping, underbase chokes, etc. You could let it ride and flash each color but why make extra work for yourself. Practicality and efficiency also come into play. When at the color separation stage, thinking beyond the digital file in front of you is a big part of it. How do you want your film positives to look? Visualizing how inks (colors) are going to appear on the substrate and ultimately, the finished print, all nice and crisp. A basic knowledge of color theory helps. 

Successful, butt register, wet on wet spot color printing on textiles, in it's most basic form, depends 110% upon the usual suspects - screens must be at optimum tension, boards level, off contact minimal, high mesh counts, sharp squeegees and so on.

Regarding smashingmagazine, it's always interesting, even entertaining, whenever the paper print industry produces how-to articles about screen printing. It's like they're stuck in some 1970's time loop when virtually all direct textile screen printing consisted of trapping every color, inks glopped merrily over each other, using screens that had more in common with a trampoline than a drumhead.

[Gilligan]

...using screens that had more in common with a trampoline than a drumhead.

So you've been to my shop?

But in all seriousness, I don't have the perfect setup yet... I will be more ideal soon... just haven't got my retentionables up and running yet, which isn't going to happen before this job.

So I'm looking at some statics with about 13n tension.

[Frog]

I was pleasantly surprised, some years back, to find that most any decent manual press (adjusted properly) and relatively decent static frames, are capable of holding butt registration, and printing WOW, with the most noticeable issue being the need to wipe the screens clean sooner than with uber-tension rollers. This ink offset actually becomes a helper in filling in tiny gaps after a few impressions.

Grief can also be brought into the equation with a heavy hand and too much squeegee pressure that tends to stretch a low-tension screen image, buggering up the registration.

[jasonl]

...using screens that had more in common with a trampoline than a drumhead.

So you've been to my shop?

But in all seriousness, I don't have the perfect setup yet... I will be more ideal soon... just haven't got my retentionables up and running yet, which isn't going to happen before this job.

So I'm looking at some statics with about 13n tension.

as long as all of the screens you use are close to 13n, you can achieve great results.

[alan802]

If those inks are poorly formulated for wow printing then you'll have to wipe the screens down on a regular basis.  I tried a new black ink on Friday for a 2000 piece job and had the black as the 2nd color and 5 screens going on wow after it.  It's a terrible black ink and after 12 shirts they started popping and then sticking on the 3rd screen.  The black was building up badly all the way to the 7th screen to the point I had to scrape the ink off with a putty knife then wipe the screens down with screen opener.  I then went and got my QCM wet on wet base and mixed it about 40% with that same black ink and started running the job again.  We got 600 prints done before we stopped and I looked at the bottom of the 3rd and 4th screen and the buildup was there but not to the extreme and not to the point where we had to scrape the ink off with a knife.   I did wipe down the 3rd and 4th screen but not the rest of them. 

Moral of the story, some inks just will not work for wow printing even if you are using 30 newton screens like we were.  But a lot of the problems with wow printing can be lessened by using higher tension, just not all of them when the ink is clearly the issue.

This is also a good plug for the qcm wow base, it really works great.  It turned the worst wow black I've ever used into one of the best performing wow blacks I've used. 

[hazeremover]

just haven't got my retentionables up and running yet, which isn't going to happen before this job.

So I'm looking at some statics with about 13n tension.
[/quote]

Retentionables are, of course, the cadillac of screens but properly tentioned stretch and glues perform well for the majority of textile screen printing, manual or auto.

[arttex]

Problems with wet on wet printing is mostly associated with the particular ink reaction to the heat. Even with the inks not recommended for wet on wet printing you can have decent runs if you are printing on light fabrics, without flashing (you will have build up, but with cold pallets it wont become too thick and sticky). However if you try to print with the same inks on the white underbase or with some flashing between the colors, that's where the problems occurs. And the real problem is not just an usual buildup on the consecutive screens. When printing with water based inks you will also have buildup (sometimes it's even good and desired to have it), but you wont have any pops or after tack of the screens. Problem with plastisol inks is in their nature to gel at higher temperatures, that buildup becomes sticky taking more and more ink, and after some time becomes so thick and solid that can't even be wiped with a cloth. And we know that pallets on auto presses can easily reach 150 F even with just one flash.

So, after this, one can think this way: how great would that be if I can print water based inks on top of the under base. It will be some build up, but they won't gel, they wont become sticky. Yes, but you can't print water based on top of the plastisols, someone will say, and you can not make white under base with water based inks. But, that's exactly where the catch is. I can see that in US term "water based inks" is mostly associated with TRANSPARENT, soft hand, inks. However, there are also opaque water based inks (including whites) that can be also used as a under base. Now someone will say: but knowing that water based inks evaporate fast and are very temperature sensitive wouldn't those hot pallets make the screens clog? Well, few years ago opaque water based inks and water based whites were notorious for drying on the screens very fast, heavy flooding immediately after the print was a must and even then cleaning the screen with water was done on regular basis during the print run. Today, there are some very nice OPAQUE water based inks, whites and bases, with ND ("no dry") attribute. They can be left on the screens for 1-2 hours with no fear for clogged screens, they can be printed trough very fine meshes and they can be used for very nice underbase. What is usually used for over print colors is 50/50 mix of TRANSPARENT water based base (like you all know) and OPAQUE water based base, matched with appropriate pigment concentrates to desired Pantone color. We printed a lot of jobs on this way (when customer demands only highly eco responsible inks (no plastics, no oil, no discharge) and we never had any issue. There is some learning curve of course, but even for simulated process results can be as much good as with plastisol inks, with no pops and tacks and considerably softer hand comparing to plastisol prints.

Just thought maybe this can be good direction for some to think about.           

[Gilligan]

Thanks for that post Arttex, I've seen some of your stuff that you posted on DS and you had some VERY sweet prints.

I of course barely have any experience with plastisol so I'm still a bit away from waterbase but it is on the list of things to check out.  This made for some interesting thinking going forward.

I THINK my cotton white is Union Ink UltraSoft... but I'll have to double check, my gold will probably be Wiflex Vegas Gold, my Red will be Union and the Grey will be custom made with the cotton white and a Union Ink Black.

Oh, and for the record, I'll be printing this on a manual 6/4 Legend so platens should get TOO hot.. especially if I take the time to hook up my auto base flash unit (one more thing on the list of crap to do!

[Frog]

No biggie, but your white is most likely not Ultra Soft as that is their relatively soft hand translucent line for light garments. It's probably Bright Cotton White, a vast improvement over their whites back when I started! It was their white which taught me quickly, that more than one brand of ink can be represented in a shop. Whites are a breed of their own.

[Gilligan]

You are right Frog... now that I read it in type I remember it.