Screen Printing

written by: Cory Q

Being a modern man, I turned to the most obvious place for All Things Factual Presented by Learned Professionals: YouTube. I also did some reasonable Google searches which yielded about a dozen decent blogs on the subject. What that means is that if this particular How To isn't as helpful as you think it could be, there are other places to turn for knowledgeable presentation.

In about two hours of watching/reading/walking away from the computer to get a soda/wandering back again, I learned that the basic methodology for screen printing is all about the same, but the materials vary quite a bit. The basic idea behind screen printing is that one makes a screen in which part of the screen is blocked and part is not. The part that is not blocked out allows ink to be pressed through the screen and onto a surface, usually fabric. Think negative space. I'll share how the basics of screen printing work and discuss some of my trials, failures, and successes. Hopefully my messing about can benefit you!

The most popular (and what seems like most reliable) method to produce a screen is the photo emulsion process whereby the screen is coated in this thick green liquid that hardens when it is exposed to light. If you block some of the emulsion from the light, it can still be washed off of the screen and then ink can be pressed through the resultant opening.

Both screens and emulsion can be purchased at a good craft or art store (such as Dick Blick or Michael's). The screen material is called 110 mesh. I assume that has something to do with the fineness of the weave of the screen material. The finer the screen, the better the detail of the final printing.

Screens can be purchased in a number of sizes kind of like picture frames or you can even make your own, but more on this and other material concerns later. What you need to know is that both the screen and a bottle of goopy emulsion can be procured with little trouble.

Speaking of materials, once you have assembled these materials listed, you can start screen printing.
Materials needed:
Design.
Transparency (to print your design on).
Photo emulsion.
Light rig to expose the emulsion once applied to the screen.
Screen (self made or pre-made).
Ink.
Squeegee.
Platen.
Shirt (or other material to print on).
Iron.
A blank piece of paper to use in heat setting the ink.

Step 1: Design and the Transparency:
If you want to screen print, there must be something you want printed. Be it design or words, you will need that in a black and white format. When I say black and white I mean only those two colors as in a positive and a negative. Yes, there are ways to do multi-color printing but I haven't been adventurous enough to try it so I can't address that methodology. You can draw you design it by hand, use some sort of computer program to aid in design, or even use paper cutouts to make a pattern. Let your imagination run wild!

Once you have decided on your design, you will need to get that design on to a transparency. The most low tech method would be to draw on the transparency itself with a good black marker (e.i. Sharpie). The next easiest would be to print your design right on to the transparency using an inkjet printer. If that doesn't work, you can do what I do: Photocopy your design on to a transparency. I happen to work in an office that is fine if I make a personal copy once in a while. Once you have your transparency printed/drawn/prepped, it's time for Step 2 which is...

Step 2: Screen Prep:
This is the part in the process where the screen and photo emulsion come into play and is also a good time to start talking about the my background experiences and the two differing paths I have taken to screen prep and exposure.

The first attempts I made at screen printing I used wooden framed screens purchased from Blick Art Supplies. I found these to be pretty easy to deal with. They came in set sizes (like picture frames do). The only problem here was the smallest screen had to still accommodate the squeegee used to smooth out the emulsion, which it did with a zero clearance. The other problem was availability of screens. The nearest Blick to The Fortress of Q is about half an hour away and often they would have only one screen in stock.

I have since moved to a YuDu machine (YD from here on out). The screens for a YD are a single, set size (Screen size: 11x14 inches, Overall size: 19x25 inches). I should mention here that screens have front sides and backsides. The front is the side that is up and has ink applied to it in the printing process so the screen material itself is flush with the printing surface.

Besides the difference in screens themselves, there is a difference in emulsion format. The Blick screens use a liquid emulsion from a bottle that is poured onto the screen and then evened out with the squeegee. YD uses an emulsion sheet that is backed with plastic on one side and is smoothed onto the screen. I had good luck with both emulsion formats with a little practice. Though YD is less messy over all, it is also more expensive. Two emulsion sheets (they come prepackaged in a light safe tube) costs $20, or basically $10 a design. A single bottle of emulsion fluid from Blick was I think about the same cost but I was able to do at least six screens and had some left over, though once the bottle is open it needs to be refrigerated. Such is the difficulty in working with chemicals.

To receive the design, there has to be a layer of this light sensitive emulsion on the screen as I have said before. This application needs to be done in a "light safe" space, or what is commonly called a dark room. For my dark room I use a bathroom and light it with a very low wattage orange bulb and a green LED. This is born more from what was around the house than intentional design. That being said, having two different colors of very low intensity light does help with being able to see everything. One color of light only gives very little contrast for the items you will be working on.

If you are using liquid emulsion, pour some of the chemical (while in the dark room) onto the screen directly. Even out the emulsion with a squeegee. An even layer on both sides is important. Use the squeegee to remove excess emulsion as well (which can be returned to the bottle) from both the front and back of the screen. If using YD, you will spray down the screen with a spray bottle and apply the emulsion sheet to the back of the screen (that is the flush side) and then smooth the sheet onto the screen. I’ve found that with YD that spaying the screen again once the sheet has been applied is helpful. Plastic side down, I then set the screen on a solid surface (I used the toilet lid since I use a bathroom as my dark room...) with the emulsion sheet on the bottom and the mesh on top and using my fingers and a squeegee make sure that the sheet is evenly applied. This is a little messy as the emulsion will press through the screen, but it gives a nearly perfect surface every time.

Once the screen has a nice even coat of emulsion (from either method) and is resting easy in a dark place, it will need to dry. This can take a couple hours. You can use a fan to help this along. In the case of a framed screen from Blick or self-built frame, a box fan is a very good option. YD has a slot in the body of the machine just for this purpose (dark and with a fan). The downside with the YD is the fan is small and runs in twenty minute cycles. Even with the YD fan and the fact that the emulsion in sheet form has less moisture involved, the screen will take an hour to dry. Like all projects that take drying time, you are well advised to plan for more drying time than less. Just be patient.

Step 3: Exposing the Screen:
In this part of the process you expose the emulsion on the screen to light. Upon doing so, the emulsion hardens. The emulsion not exposed to light (covered by the transparency with your fancy design on it) remains unhardened and can be gently washed out afterward. That washed out section is where the ink goes through.

This is the part of the process that I found to require the most technical equipment and procedural technique to accomplish correctly. If you posses some technical know-how, you can build your own light rig. If you don't, you can cobble one together out of pre-made parts. There is of course a third option of just buying a rig as well. I tried the second option after being scared off by the first option and finally moved to the third option.

What I did was hang a powerful clear light bulb in a standard reflector lamp over my bathtub. What I should have done was build a table out of plexiglass and wood with a fluorescent light underneath and a solid wood top.

The advantage to the rig I first built was that I used materials I already had around, built the rig to fit the space (remember I use a bathroom as my darkroom), and it ultimately did work. The down side was the exposure time was always a bit precarious, I burned at least one screen, and it was clunky in both set up and storage. Even after doing at least six screens this way, I was still very uneasy about the amount of exposure time needed. I ranged anywhere from five minutes to twelve minutes. On the low time side the screen didn't set. On the long side the transparency warped from the heat leaving a poor burn out image. I simply placed the transparency over the emulsion coated screen, turned the light on, set a timer, and walked away.

Here is what I should have done: Buy a florescent ballast at Home Supply Store and make a platform to go over that light using wood and Plexiglas. If you go this route, make sure the ballast has sides and is a plug in kind (not hardwire!). Here the transparency would rest on the Plexiglas and the emulsion coated screen would be on top. The front of the screen (ultimately now on top) would need to be covered from extra light because the emulsion should only be exposed to light on one side.

Here is what I do now: YuDu. This rig has some very good advantages and some things I don't like. One thing I really like is the built in timer. The work for figuring out the time exposure of the screen has been pre-calculated by those more skilled than I. The platen (we'll get to what that is in a minute) has very handy placing tabs so it functions to cover the back of the screen from ambient light exposure. Just hit the button to turn on the light, expose, wait for the timer to ding, and you are done! I don't like the size of the YD or the cost of the materials however and as noted above, the drying fan is anemic.

Step 4: Washing Out the Design and Drying the Screen:
The ease of this step really depends on the quality of the emulsion application as well as a proper exposure time.

For the sake of example, let's just say you got the exposure time and light intensity right. If so, washing out the design is pretty easy. The emulsion will be set but it won't be hardened yet meaning water and a little physical agitation will remove the unexposed design. As such: Run the screen under lukewarm water. While doing that, gently using just your fingertips, rub the design. Make sure to do this on both sides of the screen. The emulsion will mostly (about 75-90% in my experience) wash away in around twenty second with little help. The emulsion that remains in the design area is really the part you will want to rub out with your fingers. Be careful not to rub too hard! The difference between a decent screen print and a fantastic screen print is the sharpness of the edge line on the screen and at this point if you rub too hard you can abrade the very emulsion you want to keep to make that line razor sharp.

Now let's say, like my first attempts, that the process wasn't perfect. You may encounter the following issues:
-If the emulsion is too thick or overexposed, there will be trouble in removing the emulsion from the screen.
-If the emulsion is underexposed, not only the design but the supposedly hardened emulsion will also come off the screen.
You will be able to tell right away if the screen is underexposed as the emulsion will start to liquefy again with the application of the lukewarm running water. If the screen is over exposed the running water won't wash the design out without help from your fingers or possibly a soft tooth brush.

Once you get the design washed out you will need to completely dry the screen again. The inks are water soluble so having a wet screen is bad news. See the notes in Step 2 about fan drying, etc.

Step 5: "What is a Platen?” and Flooding the Screen.
A platen is the device that holds what you want to print on in place during the actual printing. This is the part of my initial foray into screen printing where I went off the rails. I attempted to build a little platform that I could place a t-shirt on and then clamp the screen onto that platen. While I did technically succeed in said shirt placing and screen clamping, the rig was ill conceived, just as ill constructed, and most importantly wasn’t overly stable to print on. Think of trying to chop carrots on a cutting board that slides all over the counter top.
I do think one could build a platen that would work. I just didn't think my design through as well as I could have. The YD has a wonderfully clever platen design that not only hooks into the machine for more stability, it has a sort of double-stick tape set up so the shirt stays put on the platen. If I was building my own rig again, I would totally steal those ideas.

This is the YD platen.

Once your screen is dry from washing the design out, you are ready for the next step. Get your shirt set all straight and level on your platen. Once your shirt (or whatever you are going to print on) is set, you will need to "flood" the screen with ink. This step is accomplished before the screen touches the fabric. The YD has a hinged lid that the screen sits in so you can flood the screen, then swing it down into place on top of the fabric. Also a good design feature. Anyway, back to the “flooding”. The point of this step is to ensure an even distribution of ink into the screen so that the ink will also be even in printing. Run a line of ink above your design on the screen. Then, using a squeegee, pull the ink across the design. Make sure the entire design is covered in ink. I tried using a brush for this step but it was a disaster. I pushed the ink too far into the screen and it pooled on the back of the design making the print sloppy.

Step 6: Actual Printing:
This is where the magic happens! This step really has just three things to remember: Press the flooded screen firmly onto the fabric, press firmly with the squeegee across the design, remove the screen carefully. There isn’t much of a trick, after all of that, to the actual move of printing. Keep a tight pressure of the screen to the material you want to print on, swipe the squeegee across the design with firm and even pressure. When you remove the screen, do so in a straight up manner. That should help keep the design from getting smeared. If you are going to make another print (like you want to print the same design a number of times in a row) you will need to re-flood the screen each time.

I made this video of steps 5 and6 just for you.

And that's it! Ok, there is one last thing. Make sure to wash the ink out of the screen and off the squeegee before it dries.

Step 7: Heat Setting:
Before you run off and flaunt your new creation, let the ink dry overnight. It will most likely be dry in just a couple hours, or possibly less depending on the size of the printed area, but why chance it? Once the ink is dry, it will need to be heat set to maintain its permanence. The basic heat setting method is to iron the ink through a blank sheet of paper. Some inks allow for put being put in a clothes dryer on high instead. Make sure to read the ink container for exact details for the ink you use. Oh, also, make sure the iron is not using steam but just a dry heat, generally on a high heat setting, like cotton. Remember water is the enemy of unset ink so steam will destroy your printing. Once you have ironed both sides of the design for a couple minutes, you have a completed project that will stand the test of washings and wearings!

I think that screen printing is one of those skills that just about anyone can learn. The only barrier is the cost of materials and the initial equipment cost. If you go the easy equipment route and get a YuDu, it will cost somewhere around $200 and it is a big machine to find a storage place for. If you decide to build your own exposure and platen rigs you can do it (much better than I did) for around $80. The screens are reusable. The emulsion, even once hardened, can be removed by chemical means (also available at craft stores). If you treat a screen carefully and aren't concerned about keeping a design, you could get a lot of mileage out of a screen itself. I have done over 120 prints (of the same design) from a single screen. This is a good thing because each screen itself is about $20. The expensive part of this is the emulsion. Whether bottled or in sheet form, it is going to run about $10 a design. If you are doing just a single print (I like my shirts totally custom!) this gets to be expensive. If you are thinking of making even a limited run of shirts (let’s say 20 or 30) this economy makes more sense.

My opinion on whether it is wiser to build a rig or buy one is split. I really like the YD, but during the course of writing this article the situation has moved from being able to get screens, inks, and emulsion sheets for the YD at local and very convenient locations (JoAnn's and Michael's) to being only able to get supplies via Amazon.com and like outlets. I can only imagine how badly YD mucked up that business relationship to cause this change. What it means is that I have a great rig and no supplies because of the proprietary nature of their screens and emulsion sheets. Building a rig appeals to my DIY sensibilities and allows for possible dis-assembly and more unique storage options but the difficulty of accurate exposure times really is a Grade A Hassle. In terms of quality of materials, I found that YuDu and Blick supplies are equal.

Wrap Up:
What I've learned from my experiences in this endeavor is that the theory of screen printing is easy to understand. The technique for screen printing isn't too difficult especially with a little practice. The machinery of screen printing is a hassle. The approach I have given above is equipment intense but it doesn't need to be that way. I found a blog (which I can't seem to find again or I would link to it) where a crafty woman used sewing hoops, old nylons, and Modge Podge glue to make and print her screens to more than satisfactory effect.

I've also learned that like any artistic undertaking there has to be room in the mind to embrace that the first few attempts will not be great. Practice makes perfect. I've also learned that a lot of the ideas I have for awesome custom shirts have been done before. I am dauntless in the face of that last piece of information. Lastly I learned that doing mass runs of prints isn't very hard but if you do them for a theater company they probably won't appreciate your efforts and want you to do this for free. In other words, do it for money or do it for fun but keep them separate no matter which way you go.

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