Melanie and I are on a five person team for this year’s Mud Run. The MS Society does what they can to promote a team spirit and one of the things they request is some sort of team uniform. Because the race is already fairly expensive, we decided to go the cheap route. My teammates are going to provide me a white t-shirt and I’m going to get our team logo on it somehow.
Because at least some of these shirts are going to be technical t’s made of wicking polyester, I thought screen printing would be our best chance at something that looks decent and may actually stay on during the race. This meant that I had to learn how to screen print. Below is what I’ve learned about the process. I’ll post pictures of the finished shirts when I’m done.
The concept of screen printing is very simple: 1. Get a fine screen. 2. Block out the parts you don’t want ink to get through. 3. Put ink on top of the screen 4. Push the ink through the screen onto the printing surface 5. Remove screen and cure ink.
You can do this in a number of ways from the most basic hand made stencils, masking tape or found objects all the way up to photo sensitive emulsions. The ink can be anything from spray paint to fabric ink specifically designed for screen printing. I’m going to be talking about a lower cost alternative to the way the pros do it.
Step 1 – Collect supplies.
Old crappy clothes
Screen material – 110 mesh screen printing fabric, translucent curtain fabric, etc.
Frame – old picture frame or wood to make your own
Staples – shorter than the thickness of your frame
Speedball Diazo Sensitizer
Speedball Diazo Photo Emulsion
Large emulsion spreader – plastic wallpaper smoother or scoop coater (better)
Red light/darkroom light (optional)
Completely dark place to put screen – closet, cardboard box, etc.
Something to support screen horizontally – four spray paint caps, thumbtacks, etc.
Clear overhead transparency suitable for photocopier or laser printer use
Black and white design for t-shirt
Sheet of clean clear glass that fits inside frame
Bright light – 250w work light, (2) 100w work lights, the sun, etc.
Shower, large sink or garden hose with spray head
Clear packing tape or screen printing tape
Stiff squeegee or plastic putty knife with sharp edges removed
Fabric screen printing ink
Cardboard – large enough to fill the inside of the shirt
T-shirt – must be porous material that can take heat – not nylon
Step 2 – Construct frame.
You may get a picture frame from a thrift store. This will provide the frame you need and the piece of glass.
I didn’t see anything large enough that would work for me so I built my own from a scrap piece of poplar I had in my shop. I used glued half lap joints and the finished product is plenty large and strong enough for this purpose.
Step 3 – Attach screen material to frame with staples.
When selecting your mesh you want something that is strong because you’ll be pushing on it with some force. You want something that is a relatively fine mesh to capture the detail of your design but not so fine that it doesn’t let the thick ink through. I got my fabric at an art supply store ($10/yd) but people have had success with translucent curtain fabric (~$2/yd) and even panty hose. Many people recommend 110 screen printing mesh for fabric. My art supply store’s version of this was “8XX Multi-Polyester Silkscreen.”
Cut the material so that it is a couple inches larger than the frame. Lay the frame on the material. Staple the material to the frame. Start with one staple in the center of one side. Pull the material tight and put one staple in the center of the opposite side. Repeat the process for the remaining two sides. Working from the center to the corners on a roughly 1” spacing, repeat the process putting a staple in one side then the opposite side, making sure to keep the screen pulled tight.
You should now have a frame with screen material tightly stretched and stapled to it (no sags or ripples).
NOTE: I chose to staple my fabric to the outside edge of the frame so that the staples would not touch the printing area and allow the screen to sit flatter on the T-shirt.
Step 4 – Wearing crappy clothes and gloves to protect your hands, add water to sensitizer and mix with photo emulsion according to manufacturer’s directions.
At $27 for the two chemicals, this is the only really expensive part of the entire process. Once mixed, if you store the goop in your fridge, it is supposed to be good for four months. There is a lot of it. I have to believe that there is a cheaper alternative and I will be looking for it for future projects. I know that I could use water-resistant glue and paint on a stencil or cut Frisket or mask with tape but that defeats the purpose.
I thought I was going to be clever and use our super accurate kitchen scale to measure out ¼ of each and mix it with ¼ the water called for. This is the only reason I bought these pricey chemicals in the first place. The sensitizer bottle is so lightweight that it has a sticker saying something to the effect of “Contents are lightweight. Bottle is not empty.” I assumed this meant it was a powder but in fact it is just a very small amount of a fairly thick liquid. I knew I would never get all of it out without mixing it with water as the directions called for. Trying to transfer it from one container to another would cause me to lose too much of the product so I just mixed the entire thing.
Step 5 – Apply mixed photo emulsion to screen using large emulsion spreader.
NOTE: This step can be messy. I did it in my garage sink. Be sure you are protected. These chemicals are nasty to get on your skin.
If you have a scoop coater, fill the trough with mixed photo emulsion about ¼” deep. Holding the screen vertically in the sink, tilt the scoop coater against the bottom edge of the screen. Wait for the emulsion to ooze up against the screen. Now in one even stroke, pull the scoop coater up the screen pushing fairly firmly to create a thin even layer of emulsion on the screen. Flip the screen over and repeat the process on the opposite side of the screen. You must do both sides of the screen at once. You cannot let one side dry first.
I cheaped out and used an old plastic wallpaper smoother. It is probably too flimsy to make good even contact with the screen. It certainly is difficult to get it to hold enough emulsion. I used an old measuring cup to ladle the emulsion onto the smoother. I had read that it was important to do this step in the dark using a darkroom light so I used a headlamp I have with the red night-vision filter in place. I think this was a mistake. I have since seen where other people do this under natural light and then quickly move the screen into a dark area. I could not see exactly what I was doing because the emulsion is so dark in red light. I’m not sure if it was the smoother, too much emulsion or not being able to see what I was doing, but I did a horrible job coating the screen. It was lumpy and took forever to dry. Next time I’m either going to make my own scoop coater or buy one. Some instructions call for coating only one side. I think if you did a perfect job this would work well but for amateurs, coating both sides is a better way to guarantee you don’t have pinholes in your emulsion.
Step 6 – Dry the emulsion coated screen.
If you were not already working under a darkroom lamp, quickly move the coated screen to an area free from any light. Store the screen horizontally with the screen side of the frame facing down. Be sure to place the frame on something so that the screen is not touching the floor/table. Allow the screen to become completely dry to the touch. This will take anywhere from 1 to 2 hours normally.
When I did this step I put the screen in a cardboard box with the corners supported by four spray paint tops. Because of my uneven, and in some places very thick, coating it took a long time for my screen to dry. I stopped timing it after 3.5 hours and just left it overnight. I’m sure the cold weather didn’t help either. I made a big mistake one of the times I was checking the screen. As I placed it back on the paint caps, it moved and I didn’t notice one of the caps shifted from the frame to the screen where it stuck securely. I did find the red light useful for checking the screen throughout the evening so I would have one on hand for this part of the process if possible.
Step 7 – Prepare the design and transfer it to the overhead transparency.
While your screen is drying you can do this step. Come up with a creative design or, like most people, just steal someone else’s. If this is computer generated and you have a laser printer, simply print the design onto the transparency. If you have an inkjet printer, print the design onto white paper and photocopy it onto the transparency. If you are creating the design by hand, either draw directly on the transparency or on a piece of paper to photocopy onto the transparency.
Make sure your design is black and white. The black part of the design will be the color of your ink. The white will be the color of the t-shirt. The black areas should be very dark. It is critical that you check your design by holding it up to the light to see if there are any problem areas. On my transparency I had to touch up some areas with a black sharpie where the toner didn’t stick very well.
Of course you can do multiple colors. You simply make separate screens for each color you plan to print. If you are familiar with other types of printing, you can separate your image into its C’s Y’s M’s and K’s, making a screen for each. This would allow you nearly unlimited printing options – even reproducing photographs. Luckily for you, explaining how to do that, or even just the color theory behind it, is beyond the scope of this post. Saved from the windbag once again!
Step 8 – While still in a low-light area, quickly place the dry screen on the black towel. Place the design transparency right side up on the screen (so text is readable not reversed). Place the glass on the transparency. Position under light source. Turn on light source. Turn off light source once exposed emulsion hardens.
The black towel prevents light leak from under the screen. The glass is a heavy flat object to press the design directly against the screen so no shadowing will occur. Be sure to that all items are clean. Large dirt particles can create pinholes in your emulsion.
The photo emulsion used to create the mask on the screen is light sensitive. You didn’t think they just threw “photo” in the title because they like words, did you? All of the areas where the emulsion is exposed to light, it will harden. All of the areas not exposed to light (under your nicely blacked-out design) will remain soft and removable. Trial and error will tell you how much time this will take. You will notice that the emulsion changes color and gets darker as it hardens. This will continue until the exposed emulsion is dark green while the protected area of the design remains a pale yellow-green.
GUIDELINES: One source said exposure to the sun would take 1.5 minutes. I would think this would be extremely variable and would not use this method. Other sources say 250W incandescent at 12” from surface = 10min. 150W incandescent at 12” = 45 min.
Everything up to this point has had a large slop factor. This step does not. If you underexpose the emulsion it will all come off in the next step. Apparently if you over expose it, you will not be able to get any of it to come off. I recommend that you document the type of bulb, wattage, distance from surface and exposure time. In this example, I used (2) 100W incandescent bulbs about 12” from the surface for 45 minutes. It worked very well.
Step 9 – Remove towel, glass and transparency from screen. Immediately rinse screen with cold water until all uncured emulsion is removed. Hold screen up to light to check for any cloudy areas. Light scrubbing may be necessary to remove all uncured emulsion.
This step can be completed in a large sink, a shower or with a garden hose. If you delay, the previously unexposed area of your design will begin to harden with exposure to light.
Step 10 – Place screen in direct sunlight and allow it to fully cure.
Step 11 – Place t-shirt on large flat work surface. Insert cardboard inside shirt to hold it flat and prevent ink from transferring all the way through the shirt. Place screen on shirt and have someone hold it or secure it with clamps.
Step 12 – Place ink on top edge of screen using a scoop or a spatula. Draw ink across design in screen with a squeegee or plastic putty knife using gentle pressure to distribute a large amount of ink over the design.
This process is called flooding the screen. You are trying to get good coverage of the ink over the entire design without actually trying to push it through the screen. I needed so little ink for my logo test that I just used a stirring stick to smear some ink on the screen. I got very good results flooding the screen with a plastic putty knife.
Step 13 – Apply firm pressure to squeegee or plastic putty knife and draw it back across the screen in the opposite direction used to flood the screen.
This step pushes the ink through the screen and onto the shirt. It is important that the screen makes good flat contact with the t-shirt. You have to apply a decent amount of pressure. On my first attempt I had some areas that were light on ink. I pressed harder the next time with much better results.
Step 14 – Immediately flood screen with ink again (if doing multiple shirts). This prevents the fast drying ink from setting up on the screen. Once all printing with screen is complete, immediately wash screen to prevent ink from setting up on screen.
Step 15 – Set shirt aside to dry (about an hour). If there are other colors or elements to this design, repeat from Step 11 until design is completely transferred to t-shirt, waiting until ink is dry to apply the next layer.
Step 16 – Keep cardboard inside shirt. On ironing board, place cloth rag on top of shirt. With iron on hottest setting, iron design for at least one minute (preferably 3-5 minutes). Turn the shirt inside out and repeat Step 16. This step helps prevent the ink from coming off when the shirt is washed.
Step 17 – Wear and enjoy.
For more information on screen printing see this entertaining video.