Basics: Wet on Wet Screen-printing

There are many reasons why a t-shirt shop should learn how to screen-print inks using a wet on wet technique.

The primary driver though, is simply speed.

Every time you flash, you are slowing your production output. If you are flashing after every color, you are crawling by at a snail’s pace instead of zipping through a job.

This article was written to give you some valuable tips to consider to screen-print inks wet on wet for apparel in your shop.

Wet on Wet Theory

To start, let’s discuss some theory.

Whether you are printing manually or with an automatic press, the way you print is a mechanical process. Each step along the way in that process is a variable.

If you take a deep dive into how each of these variables plays out during production, it’s easy to see how a change in one variable can influence the outcome…in positive or negative ways.

Many shops struggle with screen-printing wet on wet ink because they do not have a firm grasp on these different variables. It’s interesting, as I see a lot of shops blaming the ink or even the press for their challenges. You know who you are.

Other folks don’t know why they can’t print wet on wet and after many frustrating attempts, simply give up.

In this article, we are going to briefly review each of the variables that can make a difference for your results.

But first, when thinking about how to control wet on wet screen-printing here are a few factors:

  • Art
  • Screen mesh count
  • Screen tension
  • Emulsion thickness
  • Screen off contact
  • Ink viscosity
  • Print order of the screens
  • Underbasing
  • Squeegee durometer
  • Squeegee pressure
  • Squeegee angle
  • The combination of everything above

Art Basics for Wet on Wet Screenprinting

Here’s a question for you. When thinking about creating art for your customers, do you put any thought into how those folks in production are going to print it?

From dealing with sales and art staff for a few decades, I can tell you that most sales and art departments have very little understanding of what happens after the art file is separated for production.

Don’t think so?

When was the last time your non-production team spent any time in the screen room burning screens or on press running a job? (For smaller operations, one person might wear many hats and do everything, but I’m talking about bigger shops here. ) That’s who usually gets stuck.

If the idea is to create designs that can be set up and printed faster using a wet on wet technique, there are a few art tricks that you can do to help your shop out.

Let’s explore these:

Tip One: Colors Don’t Touch

Yeah, I know. This might be hard to pull off with some aspects of logos and art, but it is one to consider. One of the challenges with printing wet on wet is that the edges of where colors meet can become blurry.

Want to make this a non-factor?

Design the file so that the colors simply don’t meet. When this becomes a design parameter it isn’t so hard to pull off. It’s just creative planning.

Use the shirt color more. There is a fancy art term for this called “negative space” or “white space”. They probably still teach that in design school I’ll bet.

Can you screen-print wet on wet and have colors touch (which is also known as butt-registration)?

Of course!

However, if you want to eliminate problems look at managing this variable as much as you can. Especially if you are building the file yourself.

This idea is all about controlling this one variable.

Tip Two: Big Ink Areas Matter

From a creative standpoint, nobody wants limitations. I know, as I’m a designer too.

However, if you are trying to achieve faster production by limiting flashing and printing wet on wet, the one thing that can stand in your way could be in limiting using big areas of color in a design.

So before you make that background bright yellow on a black shirt, does it really have to be that way?

What if it was a different color?

Can it be printed as color without an underbase or with a halftone instead?

Sometimes the answer is no…that’s the way the customer wants it. But, quite often this is what the in-house designer is choosing.

Therefore, before you make things more difficult for your production team, stop and consider what they have to do to keep that 12″ wide circle of PMS 109 looking like bright yellow on a black shirt.

What might work just as well and not have to be flashed?

If our goal is to print that order faster and with less ink, that might not be the best choice. Maybe you can design it differently?

Train your artists to think like printers that have to set up and run the jobs. This may mean some OJT. On the job training. Get them some time working out in production so they can comprehend what their design decisions really cost in difficulty level and more importantly, time, on the press.

The Importance of Mesh Count Selection

One of the primary factors in successful wet on wet printing is using a higher mesh count. The reason?

The thinner the ink deposit on the shirt, the easier it is to control and prevent it from picking up or smearing around.

So what mesh count tools do you have in your toolbox?

I’ve been to shops where the only mesh available was a stock of 156 screens. That’s what they use for everything.

Hey, if your only tool is a hammer all of the solutions look like a nail.

An easy way to control the ink deposit on the shirt is to step up to a higher mesh count. Start with a 230 and go up from there. What do you have available in your shop?

Use something higher than your normal “every day” screen and see what happens.

Screen Tension Matters Too

Got a few of those 230+ screens? Great!

Next up on the agenda is the mandatory discussion regarding screen tension. Do you measure yours? Consistently?

This is extremely important when printing on wet on wet.

Here’s a visual for you. I want you to think that instead of your screen and squeegee combination, we have a fat kid jumping up and down on a trampoline.

A low tension screen is the same as a low tension trampoline.

What if our trampoline has low tension and Bubba wants to play? That kid is going to hurt himself when the trampoline sinks all the way to the ground after his next big jump.

Boom! “Mommy!!!!”

But what happens when we tighten up the tension of that trampoline? After each jump, Bubba doesn’t go quite as low to the ground, he can play safer, and the trampoline snaps up faster after every jump.

The same goes with your screen mesh when you print. A higher tension screen snaps up faster as the squeegee travels across the surface.

That snap makes all the difference in successful wet on wet printing. Because Bubba won’t have enough time to smear your ink and ruin your day.

So what tension do we need?

Ideally, around 25 N/cm2. The more the better. Also, be sure when printing multicolor jobs that each screen be within 2 N/cm2 of each other as a general rule of thumb.

Use a tension meter to measure your screen tension and clearly mark them on the screen so you can make good decisions in the darkroom when choosing a frame for a particular job.

EOM – Emulsion Over Mesh

Another variable that you should be controlling in your shop is the thickness of the emulsion coating on your screens. How much thought do you put into this?

Some shops have a zen craftsmanship dedication to getting the emulsion screen coating perfect. Others have a part-time high-school kid with little training doing it on Thursdays.

Can you guess which one has better printed shirts?

My friend Greg Kitson with Minds Eye Graphics has been fond of saying that “We aren’t in the screen-printing business, we’re in the screen-making business.”

I agree.

Want more control of your screen-print on the press? Get more discipline of how much ink is deposited on the shirt with how your emulsion is applied when making your screens.

If you want to really dive into this, read Dave Dennings fantastic article about this from a few years ago “Standardization in Screenmaking”

Simply put, the thicker the emulsion on your screens the more ink you are going to lay down on the shirt when you print.

For wet on wet, we want a little less ink deposited than normal, as this is easier to control.

So if you are used to coating screens 1:2 or higher, drop that down to 1:1. (Meaning how many emulsion coats per side)

Your goal is to get about a 20% EOM. Check to see what is the thickness of the mesh you are using. For example, if you are using a 230 mesh screen and the fabric thickness is 58 microns, then the EOM target would be about 12 microns of emulsion. (20% of 58 = 11.6)

If you really want to dial this in, buy a stencil-thickness gauge so you can measure.

Your ink deposit is a variable you can control from your screen. Remember that the next time you are wondering why your print looks weird. It could just be the way your screen was set up, not anything to do with the print mechanics on the press.

Mesh selection, screen tension and the thickness of the emulsion have a lot to do with that.

Screen Off-Contact On Press

Do you adjust this? It’s a rhetorical question I know. Of course you do!

Seriously though. Are you adjusting? The reason I’m asking is that I know some printers have their presses set up the same way the technician arranged it when it was installed. Nothing has been ever tweaked.

In case you don’t know the Off-Contact is the space between the underside of your screen and the top of your platen. When you load a shirt onto the platen, the distance between the bottom of the screen and the garment is a little less due to the physical thickness of the shirt.

Maybe you don’t change this in your shop. Not on a regular basis anyway.

T-shirts, fleece, bandanas, whatever…it all prints the same. But not with the same result, right? For some, this is a head-scratcher.

Why am I bringing this up?

Well, if your off contact hasn’t been adjusted is it any surprise that your ink may be smearing on the shirt or picking up excessively on the back of a screen occasionally when you print different types of garments?

While there are plenty of presses out there, and as I can’t possibly know what you are using, you need to know how to change and set up your screens for the best possible print. Your screen off-contact plays a key role in success.

As a general rule of thumb, about the thickness of a dime should be ok for a t-shirt image. A nickel for a sweatshirt or fleece. Higher if the garment is really thick. Your press manufacturer should have good instructions on the proper setup and how to change the off-contact with their equipment.

Keep an eye on your off-contact during the wet on wet screen-printing process. You may need to adjust this for the best possible results. Try adding a little bit more to help if you have problems printing wet on wet.

Ink Viscosity

Thicker ink is harder to print. Thinner, creamier ink is easier.

As plastisol ink is thixotropic, it gets easier to use the more you work it. Stir the ink in your bucket well before adding it to the screen. Use a paddle bit in a cordless drill if you don’t want Popeye forearms.

However, for wet on wet screen-printing, some shops thin down their ink to make it easier to print. Especially when they bump up the screen mesh counts to 230 or above.

The product of choice is usually curable reducer.

The more you add, the lower the viscosity the ink will have. You should know that some ink colors and brands already have a low viscosity level.

Be careful. Using a curable reducer is basically a band-aid.

Also, when printing with ink that has a percentage of curable reducer ink it, this may make it less opaque. For some, that may be the desired result.

However, if you want an opaque bright print, using an additive that makes the ink more transparent and duller could pose a problem.

If you have to use this, start with 2%-5% by weight and see if that makes a difference for you. Every color hue and ink brand will react differently, so this is not a one-size-fits-all solution.

Use a scale, not a random glob.

Make sure you mark the bucket with what you added by the percentage.

Screen Print Order

For the most part, everyone has learned to print lighter colors first, and darker colors last (usually). I say usually because every design is different.

The design will dictate the moves you make on the press. Sometimes printing the darkest color first is a great option. Don’t limit yourself.

For wet on wet printing, there are a few strategies that you should be aware of when planning out your screen print order.

Smaller Areas First

The “Smaller Areas First” plan for print order works as there isn’t much ink put down on the shirt to cause an issue with the next ones down the line.

Imagine if your design was a flower.

The petals were yellow, the center of the flower red and the outline and some type are navy blue. With this thinking, your print order might have the red of the flower print first because it is the smallest, then the yellow petals, and finally the navy blue outline.

Detail Last

The “Detail Last” plan has the important details that really make the design happen print last. Which is why in our flower design, we are printing the navy blue screen last as it has key details and the type.

The viewer’s eye will naturally be looking at these first, so we want to print them last so they are perfect.

Underbasing

Sure, I know you have been reading this article and wondering if I was even going to mention an underbase screen or not.

My thought here is that if you can get away with not using an underbase screen, then that’s a good decision. Not all images need one. Plus, if you are in control of creating the art imagine how more productive your shop could be if that wasn’t part of the production.

Yeah I know, sometimes you need it. Like a donut. Or a shot of tequila.

But instead of only considering that is the only option, you could try something different. Think about how your production might look for jobs if you didn’t flash and used one less screen on some jobs.

For example, have you ever tried high opacity inks?

These are inks that have such a high pigment load that they don’t need an underbase to work on dark garments.

Yes, they are more expensive. But how much is that compared to the cost of that underbase screen process?

How many more jobs per day could you push out?

Talk to your ink rep and ask to try a few samples and see if they might work for you.

The Squeegee

In some shops, this is known as the “hammer”. That’s because when they are printing, their goal is mash the ink through the screen as hard as they possibly can…like a hammer pounding a nail.

You can see this too if you look at their presses and see the printed designs on their boards. The reason why they have so many opacity issues is that they are driving the ink completely through the shirt and onto the platen.

Not many customers pay for that.

Which is why squeegee control is so important. Especially with wet on wet printing.

There are a few things to keep in mind here. Durometer, pressure, and angle.

Squeegee Durometer

Quick quiz. Are you using the same squeegee for every job? In fact, the squeegees you are using are the ones that came with the press when the tech installed it. (Uh, how many years ago was that now?)

You know you can use different ones, right?

There are a few things you should know about your squeegee rubber. The first is that the cheapest squeegees are made from actual rubber. The best are made from polyurethane. These are the most durable.

To rate the rigidity of the squeegee blade, the industry uses the term “durometer” and gives the hardness a number. The higher the number the firmer the blade. Softer squeegees generally leave a thicker deposit, while harder squeegees print less and are better for detail.

  • 50-60 durometer squeegees are considered soft. They are great for printing specialty inks, thicker ink deposits, or controlling fibrillation.
  • 70 durometer squeegees are considered medium grade. This is a general, every day hardness for a squeegee
  • 80-90 durometer squeegees are considered hard. They are harder to bend and when used leave a lighter ink deposit. These are used with high mesh counts, halftones, and four-color process printing.
  • Composite squeegee blades are very popular too. They have the print facing edge to help with the ink deposit, but the rigidity built-in for better control. You might see a 70/90/70 triple-durometer squeegee in a lot of shops.

I’m mentioning everything above about squeegee durometers because what you are using on press can determine your final print result. All things being equal, printing with a soft squeegee can yield a different result than a harder squeegee.

Keep this in mind when you are locking in your squeegees and floodbars. Ask yourself, “What is the desired print result we want to achieve with this particular image?”

If you are having problems with the print or stepping on another color down the line, how could simply switching out the squeegee durometer affect the result?

Squeegee Pressure

This is the amount of force that is being applied to the screen when you are shearing the squeegee during a print pass. It’s Bubba on the trampoline.

The goal should be during the printing motion to use just enough downward force to shear the ink through the screen so that it rests gently on top of the shirt.

But yet, I’ve been to shops where the squeegees blades are routinely bent in an “L” shape with a crazy amount of pressure. Just because the press can move the squeegee at 100 psi, doesn’t mean that’s a good idea. The press operators spend an inordinate amount of time chasing problems such as ink bleeding, opacity, and ink pickup on other screens.

Excessive squeegee pressure can cause all of this.

Be careful!

Squeegee Angle

Then there’s the angle of the squeegee to contend with too. You want the squeegee to be more upright, than laying down. The more the squeegee lays down, the more pressure you have to exert to get the blade to print the image onto the shirt. Especially if you are using a squeegee blade that doesn’t have a crisp, sharp edge.

Instead, use a nice sharp squeegee, with a higher angle, and less pressure.

When dialing in the print during set up, try to use about ten degrees from vertical to start. With a sharp squeegee and minimal pressure, you should be able to print and clear the ink so the ink drops down through the screen and rests right on top of the substrate fabric.

Putting It All Together

If you are struggling to get jobs like this to print correctly, don’t worry. You aren’t alone.

If you take one thing away from this article I want you to realize that it is the variables in the process of printing that cause most headaches.

Remember, a good chunk of these can be engineered out simply with how the design is built and separated.

But, if you don’t have control of the art and need to print wet on wet, look to a few key areas.

  • The screens. Are they built properly? The right mesh counts, EOM, and tension?
  • The press. Set up properly with good off-contact? Boards warmed up and ready to print?
  • The squeegees. Ready to rock and roll? The right durometer, angle, pressure, and speed? Are the edges sharp?

If something isn’t working the way it should, take a minute and walk backward through the process to determine what variable is throwing it all off.

You can do it!



“If everyone is moving forward together then success takes care of itself.” – Henry Ford

“The chief function of the body is to carry the brain around.” – Thomas Edison

Time is more valuable than money because time is irreplaceable.” – John C. Maxwell