Screen Printing

Screen printing is a faster method of painting fabric with a stencil. It is ideal for printing complex or repeat patterns. If used quickly you can do several prints in a row with out the ink drying in the screen. You can use the same screen with a different color after washing and drying the screen. If you want to print multiple colors with multiple screens, you will need to let the first application of ink dry then apply the next, working from the lightest to darkest colors of ink. 

There are two methods of preparing the screen. You can trace an image onto the screen and fill it with drawing fluid or "burn" an image onto the screen using sunlight or a plant grow bulb. Screen filler is applied to prevent ink from passing through the screen in places it is applied.

Drawing fluid acts as a resist the same as artists masking fluid. It protects the drawn image from the screen filler. Washable gel glue works fine as a resist because it's very thick and doesn't drip. The screen filler is squeegied on after the resist dries. After the screen filler is dry, the resist is removed exposing the open meshed image. Latex paint works as a filler for this method because it doesn't drip and it dries hard. This is a cold process method that doesn't require baking.

Image burning gets its name from the appearance of an image being burned onto the screen by negative exposure. It is similar to the process of exposing photosensitive chemicals to UV light to burn a negative image onto paper, as in photography. Screen printing, however, isn't nearly as tedious as developing film. The screen is filled with photo emulsion mixed with photosensitizer that hardens it upon exposure to UV light. A deep black image is printed on acetate and laid face down on the dry emulsion. The emulsion is still removable at this point because it hasn't been hardened. The acetate is placed on the screen, print side down with a glass sheet over it to weigh it down. The black ink blocks out light preventing the emulsion from hardening beneath it. The screen is then baked in the sun until the emulsion is hard. The emulsion under the acetate is then removed exposing the open meshed image.

You don't need a special frame for each stencil. You can stretch the screen in a quilting hoop and remove it when you're finished. You could also use a picture, window, or deckle frame. The type of ink used for screen printing is actually thickened pigment ink. You can purchase it or make it yourself using pigment or dye.

Quilting Hoop, any size, square, round, or oval. Do not use a border hoop or one attached to a stand.

120 Mesh Monofilament Buy 3 yards from China on eBay for $8.88. An alternative is panty hose.

Elmer's Washable Gel glue is a substitute for drawing fluid.

Richeson Natural Bristle brush assortment for brushing on drawing fluid or gel glue. $14.59 at Blick Art.

Latex House Paint, flat black is used as a cold process screen filler.

Photo Emulsion is used to prepare a screen for the UV exposure method. $4.90/8 oz at Dharma Trading.

UV Sensitizer must be added to the emulsion at a ratio of 1 oz to 6.6 oz to make the emulsion work. Two bottles are required. $3.99 each at Dharma Trading.

Quick Dry Inkjet Transparency Film (acetate) $22.50/50 sheets at Walmart.

Non Glare Acrylic sheet 8x10" for $3.12 at Home Depot. Used for weighing down the transparency on the screen and as a light table for tracing. The glass from a picture frame can also be used.

Photo Emulsion Sheets are $29.99/3 sheets from EZ Screen Print. You don't need these, but they are an alternative to traditional photo emulsion and stabilizer. They must be kept in a cool dark place and have a 6 month shelf life.

Squeegee available in various sizes from Dharma Trading for $9.29-16.85. You can also use a slanted palette knife for small applications.

Versatex is the best ink for fabric. Starter sets are available from Dharma Trading for $17.39 each.

Rit Powder Dye $2.98 at Walmart. Rit now has all their dye color formulas on an iPhone app. They are no longer available on their website.

Jacquard iDye for Natural Fabrics $2.99 at Dharma Trading.

Dharma Trading has their own line of fiber reactive dye available in 150 colors for $2.95-6.25/2 oz. The benefit is that it comes in jars instead of clumsy packages.

 

Alex Artist Colors on Etsy sells artist pigment for as low as $2.75/30 grams. That's the best price I've found and they have an excellent selection of ochres and oxides direct from Cyprus.

Super Clear high viscosity thickener for screen printing ink $6.95 at Dharma Trading. You need this if you intend to make your own ink from dye or pigment.

Vegetable Glycerin $4.89 at Walmart.

Materials

Paint brush

Toothbrush

Roll plastic

Foam 

Acrylic sheet or picture frame glass

Acetate sheets

Plain paper 

Adhesive Vinyl shelf liner

Xacto knife

Screen

Frame

Painter's tape

Squeegee 

Ink

Plant Grow light (optional)

Screen Printing Ink

1 Tad Pigment or natural fiber dye

1 Dash Glycerin

8 ml water

1/4 tsp Super Clear

Palette knife #61

10 ml beaker

This formula is enough for a single application. If you need more, you may want to use dye as pigment can get expensive.

Contact Paper Method

This method uses the same sticky vinyl for lining shelves. Draw or trace an image onto the paper side and cut it out with an Xacto knife. Remove the paper and press the contact paper onto the bottom of the screen, making sure there's a little overlap. The vinyl is reusable for as long as it stays on the screen. You can also cut strips of vinyl and stick them to the screen for printing stripes.

Drawing Fluid Method

The drawing fluid method is good for simple shapes. Print or draw an image on a sheet of plain paper or acetate. Place the paper with image on an acrylic sheet and the framed screen on top of it so that the screen is against the paper. Use a permanent marker to trace the image on the screen.

Elevate the frame corners with 4 items of identical height. Trace over the marker lines with the glue using a precision bottle or a brush. Apply the glue lightly, just enough to saturate the mesh without bubbling.

Once the glue is on the screen, take a good look at it. If you see bubbles, thick or sparse areas of glue, remove or add some. It needs to be even. Let it dry flat. Don't use a fan or hair dryer; it will push the glue out of place.

Pour a bead of the latex paint across the screen along one of the two short lengths of frame. Use a squeegee to drag the paint all the way across the screen, covering the glue. Try not to create too much overlap. Thick areas should be leveled. If you have too much paint (bumps, lumps, or bubbles), pick up one end of the screen frame 45 degrees and drag the squeegee from the bottom up. The excess paint will collect on the squeegee blade. Use a credit card or a similar item to transfer the excess paint back into the can. Follow the same steps as with glue for drying the screen.

When the screen is dry you can remove the glue. To do this, set the screen in a wet basin with warm running water. Using an old toothbrush, gently make small circles on the raised areas of the screen. Work the edges first and move across the screen following the pattern of your design. When complete let the screen dry off. This time, you can use a fan.

UV Exposure Method

The UV exposure method is best for complex images with fine detail or lettering. If you're planning to print with more than one color or screen, make registration marks on the screens and fabric first.

Print 2-3 copies of your image on acetate sheets. You may want to have them printed at Staples rather than use up all of your ink. Stack each of the transparencies on top of each other to create a complete "blackout" of the image and tape the corners together.

Add a small amount of water to the sensitizer and mix it up. Use a small clean paint brush to mix it and get the residue off the bottom. Mix the sensitizer (black liquid) into the photo emulsion bottle (bluish liquid) and stir until it becomes a slime green color.

The bottom of your screen is the non-recessed part (i.e. the part that is flush with the bottom of the frame). Turn your screen so the bottom part is facing up and insert a pushpin into each corner. This will provide "legs" for your screen to sit on while it dries.

You will want to do this step in a fairly dim room since the photo emulsion reacts to light. Spread a small amount of the photo emulsion on one side of the screen bottom. Use a squeegee to spread a thin layer of the emulsion across the screen. Flip the screen over and repeat on the other side. Continue flipping and spreading until you have a thin layer of emulsion across the entire screen.

Place the finished screen right side up in a cool dark place overnight to let it dry.

Preparing the Screen for Exposure

Once your screen is dry, take it out of its cool dark place (but still in a dim area) and remove the pushpins. Place the screen on a sturdy piece of cardboard (so you can carry the screen into the sun easily), followed by a piece of black fabric to reduce reflection, the prepared wood screen (bottom side up), the transparencies (mirror image, face down), and finally a piece of glass to hold your image in place against the screen. If you look through the recessed side of the screen, it will read left to right.

Cover the screen with a piece of cardboard and carefully carry it outside into direct sunlight or place it under a plant grow bulb. Remove the cardboard and expose it for 2-3 minutes. If it is overcast it may take a few more minutes. The emulsion is a slime green color and as it exposes it begins to turn to a dark gray/green. Once you see it darken considerably it has been exposed.

Cover the screen with the cardboard and carry it back inside quickly. Remove the glass and transparency and take the screen directly to the sink. Your image should still be a slime green color and the rest of the screen will be the dark gray/green. Use a sprayer or hose to apply a forceful stream of water to the screen. After a few minutes the screen will start to open up and the image areas will wash away leaving a stencil. Let the screen dry and then hold it up to the light and check for holes.

Photo Emulsion Sheets

Wet your screen evenly, squeegee off excess water (emulsion dissolves in water, so do not over-wet during screen prep).

Place dull side of emulsion sheet on the bottom of the screen (non-well side).

Pass squeegee over emulsion several times to adhere to screen.

Check the back of emulsion sheet for dry spots and re-wet if necessary. Squeegee off any excess water.

Allow screen + emulsion to dry completely in a dark place for 24 hours.

Print your image on two sheets of acetate and tape them together.

When screen is dry, remove top plastic sheet from the emulsion. If any emulsion comes up, it isn't dry enough.

Place the screen bottom side up. Lay the acetate sheet on the bottom of the screen making sure it reads from right to left (mirror image). If you look through the recessed side of the screen, it will read left to right. Lay the glass over the acetate sheet to hold it down. If taking the screen outside, cover it with a black plastic bag and remove it before burning.

Burn your image (exposure times will vary depending on exposure units; if using a Yudu or plant bulb, burn for 14 min). If using sunlight, burn for 2-3 minutes. The sheet will turn to a dark blue-green color and the image will be bright green.

Gently wash out the burnt image immediately under cool running water. It will have a very light green color (if all the emulsion washes off, it was not burned long enough; if the image is very hard to wash out, it was burned for too long).

Make sure all the light green emulsion is washed out and not blocking any holes in the screen.

Let the screen dry completely before printing.

Printing

This process is the same regardless of which method you use.

Use painter's tape to cover all the inside edges of your screen to prevent any ink from leaking through. Lay roll plastic or a garbage bag on a hard surface. Place your fabric on top of the plastic. Place your screen flat onto the fabric. Apply a quarter size glob of ink at the upper left corner above the image. Pull the ink down the screen with the squeegee. Go over it a few times to make sure you have good coverage. Carefully remove the screen and allow the ink to dry. Heat set with an iron.