What is Screen Printing?
Screen printing is a process of using a squeegee to push ink through a stencil (screen) onto a material (substrate). It has been around forever.
Every aspect of screen printing is technical and pretty sensitive. For beginners this can be very frustrating and deterring. Especially when you don’t have the right equipment. Keep pushing homie and celebrate the little victories.
For todays lesson our substrate will be a t-shirt made of 100% cotton. We will also be using an ink specifically made to bind to 100% cotton.
An example of a different substrate: we print limited edition artworks onto card stock paper.
For more information check out our design process.
Step 1: Drawing
Step 2: Scanning, Editing & Printing
Let’s take our hand-drawn design from Step 1 and scan it into the computer.
Time to make a film-positive*. We do this by removing anything weird, cleaning up the edges and consolidating all the colors into one (for maximum contrast). Once the file is ready, we print it!
*A film-positive is a one-color file printed with black ink on translucent paper. We’ll use this later in Screen Printing > Step 3.
Screen printing is an involved process that has taken us over a year for satisfactory results. We are always researching, experimenting and testing new techniques to improve our craft and get our homies the best possible product.
If you’re starting out, remember it gets easier with every failure.
Step 1: Making the Screen
We use aluminum screens that are machine pulled. However, in the beginning we made our screens out of 2×4’s, mesh, wood glue, a manual staple gun and a ton of effort. We laid out both processes below:
Wood Screen Process:
- Using a circular saw we cut 4 pieces of wood out of 2×4’s and assembled them into a rectangle.
- Applied wood glue to all 4 corners and secured it with staples on both sides.
- After the glue dried, we had a sturdy frame.
- Next we stretched mesh across the rectangle and stapled 2-sides “L” of the rectangle.
- Now the mesh was anchored on 2 sides.
- The anchored mesh allowed us to pull it in the opposite direction.
- When the tension was taut we stapled a f*ck load of staples to hold the mesh nice and tight to the frame.
- Test the tension. If it’s too lose, start over.
Aluminum Screen Process:
- Place an order with a local screen-print supply company, jump in our car and scoop it up.
Degrease the Screen: After either Wood/Aluminum Screen Process we’ll need to wash the screen with degreaser to get the oils off the mesh. This step cannot be skipped!
It’s pretty obvious why we moved on from wood screens, right?
Step 2: Adding Emulsion
Next we use a scoop coater to evenly coat the screen with photo-sensitive emulsion. Emphasis on evenly.
After the screen is coated successfully, we need to let it dry in a dust-free, light-free and ventilated environment.
The emulsion takes about 4 hours to dry, if you live in a humid climate get a dehumidifier.
We normally let our screens dry over night.
Pre-Step 3: Explaining Exposing a screen
Emulsion cures when exposed to light. The ink printed on the film-positive acts as a shield blocking the light, keeping the emulsion underneath it uncured. The translucent paper allows the light to go through and cure the emulsion.
The screen now has both cured and uncured emulsion. We want to remove the uncured emulsion, which washes away using water. The cured emulsion will not wash away.
Caution: Cured emulsion can wash away, too. Be sure to use cold water and keep the wash out portion under 2 minutes.
At the end of this process, we will now have the design from our film-positive as a stencil on our screen.
Step 3: Expose & Wash Out the Screen
With our screens emulsion dry and film-positive print from Design > Step 2, we’re ready to expose the screen!
For a light source, we use a 500W light attached to a contraption we built. An exposure unit is on our list of equipment to get.
Place the film-positive on the substrate side of the screen.
Flip on the light and let the emulsion cure around the design.
With our current emulsion, this step takes us exactly 6 minutes and 53 seconds. Timing is crucial, seconds can make a huge difference.
Once the emulsion is cured, we immediately wash out the uncured emulsion using a garden hose with the classic multi-sprayer attachment.
We start with the mist and move to the flat setting.
Once we have removed all the uncured emulsion, we let the screen dry.
Step 5: Checking for Imperfections
Now that the screen is dry, we look to see if there are any imperfections or touch-ups that need to be addressed.
If there are pin holes we’ll cover them with emulsion or tape
Step 6: Taping the Edges
Almost done! Now we need to lay tape on the edges of the screen on both sides, so there is no rogue ink.
Wahoo! The hardest part is over! It’s customary to crack an ice-cold beer when completing this step to celebrate the mini-victory.
Step 7: Laying Down the Ink
With our newly finished screen, we are now ready to push ink through it!
Set the shirt down on the platen. The platen is the platform for the substrate (t-shirt). It’s necessary to use spray tact on the platen every few-dozen shirts.
Using our squeegee we will do a flood stroke. A Flood Stroke is a stroke that fills the stencil up with ink.
Now, with a solid pressure we’ll do a final pass using the squeegee to push the ink onto the shirt.
Our shirt now has our design on it, but wait, it’s wet! We use a special dryer to cure our ink. Our ink fully cures at 320 degrees for 33 seconds. All inks are different and will tell you the curing time and temperature.
Any screen printers getting rid of a conveyor belt dryer or other equipment? Please reach out.