By Christina McFall Cyanotype is a fun printmaking technique that is well-suited for printing designs on hand knits and crochet as well as other fabric. While the nature of cyanotype limits the print to shades of blue*, the deep indigo blue is beautiful printed on different colors of yarn and fabric. The process is inexpensive, simple to get started, and relatively low-toxic, making it a great printing method for crafters and artists alike. Most people are familiar with cyanotype without knowing it – in the form of the blue sunprint papers for kids. However, instead of buying pre-treated paper, you can buy the cyanotype sensitizer and use it to treat just about anything. The cyanotype image is formed when fabric that has been coated with the sensitizing solution is exposed to UV light (sunlight). Where the light penetrates to the sensitized surface, a dark blue permanent dye is formed, and where the light is blocked, the fabric stays its original color. So with the use of a negative (like an old black and white photographic negative), you can print any image or artwork. Fortunately, it’s easy to make digital negatives with a computer and inkjet printer. In this tutorial, I will show you everything you need to know to get started making your own cyanotype prints on hand knits. The process is essentially the same for any other type of fabric or paper, so experiment and have fun. * The blue of cyanotype can be changed to a few other colors through a process called toning, but that’s another tutorial in itself! (Editor’s Note: you may remember Christina from Bay Area Maker Faire – here’s a video we did about her amazing work.)
Knit or crochet piece for printing
Computer graphics program
Inkjet transparency film, available at office supply & photo stores
Original cyanotype kit, sold at photo stores
Measuring cup, plastic or glass
Measuring tablespoon, plastic
Plastic tray or small tub
2″ foam craft brush
White muslin scrap, or other lightweight cotton fabric, about twice as big as your knit piece
Non-metal brayer, optional
Safety glasses and apron, optional – but a good idea!
Plastic clothes hanger and clips or a drying rack
Hairdryer or fan, optional
Lightproof black plastic bag, optional
Sheet of glass and backing board; a picture frame works well
Step 1: Choose your yarn and start knitting! Cyanotype printing is a lot more than just blue on white (nice as that is), and the same print can look vastly different depending on the color and texture of the underlying knit piece. Here are some tips for experimenting with different types of yarn, color, and stitches:
Fiber content: Cyanotype does not print on all types of yarn equally, so be sure to test a small swatch before printing a large project. The best prints are on yarn with high amounts of cotton, bamboo, rayon, or silk. Acrylic yarn does not work because it cannot absorb the dye; however I have gotten good results with 50% cotton / 50% acrylic yarn. Wool yarns do not work well because they tend to felt up with all the washing, and the natural oils in the wool resist the dye, producing a very poor print.
Yarn color, weight, and stitch texture: Get creative with printing on different colors of yarn. Vary the texture with thick or thin yarn, or a creative knitting stitch. The possibilities are endless and are part of the fun of cyanotype printing. Keep in mind that the rougher the texture of your knitting, the bolder you will want to make your artwork.
Step 2: Create a digital negative of your artwork. Cyanotype is a photographic printing process, and the image is formed by controlling how much light reaches the sensitized fabric. There are many ways to create an image with cyanotype printing, including shadowgrams and cut stencils, but I like to use digital negatives. Digital negatives are exactly like old black and white film negatives, except they are created by printing on inkjet transparency sheets. Cyanotype is similar to black and white photography: where the negative is clear, the most amount of light is let through and the fabric underneath will turn dark blue. And where the negative is black, the light is completely blocked and the fabric will remain its original color. Likewise, where the negative is gray, the fabric will turn a shade of blue corresponding to how much light is transmitted. This way it is possible to get a full tonal range in the cyanotype print. To create a digital negative:
- Using graphics/photo editing software, create the artwork that you want to cyanotype, sized appropriately for the piece of knitting. The finished will be the same size as the negative.
- Convert the image to grayscale.
- Flip the graphic from left to right, so that any lettering is now backwards. You do this because when printing, the negative will be placed face down, ie. ink-side down.
- Invert colors to make it a negative.
- Print the finished graphic onto inkjet transparency film.
- You can learn more about making digital negatives online by searching for “digital negatives.”
- Not all inkjet inks block UV light equally. If you have trouble with your negatives being too transparent, you can darken the black areas with a sharpie. Also, look online for tips on the best settings for your printer model.
Step 3: Setting up your work area Now it’s time to set up a workspace for coating your knit piece with the cyanotype sensitizer. Ideally, you need a work area that has little or no sunlight (work at night or use curtains), but you can work under regular incandescent or compact fluorescent bulbs. You also need to protect your workspace from splashes, because the sensitizer will leave dark blue stains on any porous surface. I recommend working in a garage, laundry room, or bathroom near a sink. Use plastic or glass measuring cups, trays etc. Metal can contaminate the sensitizer. Work on a plastic tabletop, or protect the work surface with a plastic drop cloth. Protect yourself with gloves, an apron, and eyewear. Cyanotype chemistry is relatively low-toxic, but you should avoid working in the kitchen, and any cups or trays used for cyanotype should not be used for food preparation afterwards. If you bought the dry cyanotype kit linked above, then mix each stock solution following the directions in the kit. Be sure to keep the stock solutions separate and uncontaminated until you are ready to coat your knits.
Step 4: When you are ready to coat the knit fabric, mix equal amounts of Solution A and Solution B together in a measuring cup. For small amounts, you can use a plastic tablespoon, and for larger amounts a measuring cup. Once mixed, the active sensitizer is light-sensitive and only good for about 30 minutes. The amount needed depends on the absorbency and size of the knit piece. For the example swatch of 6″ x 6″, I made 2 tablespoons of active sensitizer. Tip: It’s better to mix slightly too much than too little!
Step 5: Wearing gloves, use the foam brush to lightly but thoroughly coat the top side of the knit fabric with the sensitizer. If you are working with a light-colored yarn, it will be easy to see where the yellowish sensitizer is and where the fabric needs more. The goal is to evenly coat the surface of the fabric but avoid completely saturating it. And remember, you only need to coat the area where you want to print, so if your negative doesn’t place any image material at the edges of the fabric, don’t bother coating them. If you want to print on both sides, then also coat the back of the fabric.
Step 6: Sandwich the coated knit piece inside a folded piece of muslin fabric. Using your hands or a small clean brayer (non-metallic), gently blot the excess sensitizer from the knit piece. Keep the muslin for the next step. The goal of the blotting is to have the surface of the piece adequately coated with sensitizer, but not dripping or sopping wet. The reason for this is that a heavily saturated knit piece will dry slowly and is very likely to stain – it can turn dark blue before exposure. Over-saturated fabric will also stretch out of shape as it dries, and drip, which makes a mess.
Step 7: Instead of wasting the muslin you just used to blot the knit piece, you can finish coating it and use it to make test prints later on. Using the foam brush, coat the rest of the muslin with sensitizer. Coat just enough to avoid dripping, and use the brayer to squeeze out any excess. Since this is just a test scrap, it’s okay to gently wring out the excess, but generally, wringing should be avoided as it stretches and distorts the fabric. Hang the muslin from a clothes hanger with plastic clothes pins to dry as described below.
Step 8: The treated knit piece now needs to dry completely before you can print it. The simplest way to dry is to lay the piece out on a plastic mesh or wire drying rack as shown. (Painted metal is safe for this purpose.) If, however, you plan to print on both sides, I recommend using a bit of scrap yarn and a plastic yarn needle to hang the knitting from a clothes hanger as shown above. This only works for knits that do not stretch out too much. Place or hang your knitted piece in a completely dark area, such as a closet. Allow it to air dry, with or without a small fan to help. Remember to protect the floor and anything else in the closet from any stray drips. Alternatively, you can use a hairdryer to gently dry the knit piece. Be very careful to use a cool or low heat setting and keep the hairdryer at least 6-8 inches away. Too much heat can cause staining. I often use a hairdryer to dry the piece halfway, and then let it air dry to finish. Once the piece is completely dry, you can store it in a completely lightproof black plastic bag until you are ready to print. For best results, print within one week of coating.
Step 9: Now that your knit piece is coated and dried, it is ready to print! Cyanotype is sensitive to UV sunlight, and the easiest light source is the sun. Choose a bright sunny day when the sun is high in the sky to print. Alternatively, you can use a UV light bulb for exposure. Working indoors away from direct sunlight, gather up your coated knit piece, artwork negative, sheet of glass, and flat chipboard/cardboard. Arrange them in the following order:
- Chipboard or stiff cardboard
- Your coated knit piece, right-side up on the board (be sure to remove any stray lint or fuzz that could block the light)
- Your artwork negative FACE DOWN (ink-side down) over the coated fabric
- Place the sheet of glass on top to sandwich the negative and the fabric
In photography, this method is called contact printing because the negative is in contact with the sensitized fabric. Use tape or clips to hold the contact printing assembly together and to keep the negative from shifting around during exposure. (If it moves, that can blur the final print.)
- Do not print if the piece is wet or damp. It will ruin your negative, and make a poor print!
- Use the coated muslin fabric you made in Step 7 to make test prints to determine the best exposure time.
Step 10: Place the stacked assembly outside and face up in direct sunlight, being careful not to jostle the negative in the process. Exposure times will vary depending on how bright the sun is – anything from 5 minutes to over 15 minutes is typical. Determining the right exposure time requires some trial and error, but fortunately the fabric will change colors, giving you an indication of when it’s had enough sunlight. Watch the areas where your negative is clear – they will turn from pale green, to dark blue, to dark blue-gray, to a light steel-gray. This final color indicates that the print has been exposed enough and is ready to develop. After you’ve made a couple successful prints, you will be able to recognize the right print stage easily. The piece in the photograph above has been fully exposed and is ready for development. The area with the steel-gray color will turn dark blue upon development, and the pale green color will wash away leaving just the original white knit. Tip: It is better to overexpose the piece than underexpose it, since you lose so much of the blue in the rinse water.
Step 11: When the print is fully exposed, bring it inside. Then, remove the negative and set it aside while you prepare the development bath. You can develop a cyanotype print in plain tap water, but I recommend adding some vinegar to the bath. Vinegar helps increase the depth and amount of color retained in the fabric. Mix the following in a plastic tray:
- 1 quart cold tap water
- 2-3 tablespoons white vinegar
You can multiply this ratio for larger pieces.
Step 12: Wearing gloves, place the exposed piece into the developer bath and rock it gently for one minute. The gray areas of the print will immediately turn blue, and the water will turn blue-green.
Step 13: Pour out the developer and rinse the piece in 2-3 changes of water. Next, add some water to the tray and about 1 teaspoon of hydrogen peroxide. Dip the knit piece in this mixture and you will see the blues immediately turn darker. The peroxide is oxidizing the print, causing it to turn darker blue. This would happen naturally with time after it dried, but the peroxide speeds up the process and gives you a better preview of the final dried print. In the example photo above, the lower half is darker blue from the peroxide.
Step 14: After that, wash the printed knit fabric very thoroughly in running water for at least 15 minutes. Proper rinsing is essential to the longevity of the print. I like to alternate between soaking it in water and rinsing it in running water every few minutes, to be sure to wash out all the remaining yellowish sensitizer. Thicker or more tightly-knitted yarn will take longer to fully wash. After washing, block and dry the piece as you would with any knitting. Care instructions: Cyanotype prints can be damaged by certain laundry products. Avoid using powdered detergents, phosphates, borax, oxyclean, baking soda, washing soda, and bleach to wash your printed pieces.
About the Author: Christina McFall is obsessed with all things cyanotype. When she’s not busy dyeing things blue, she blogs and sells handprinted fabrics at Meadowlarking. Check out her website for more how-to info on cyanotypes, upcoming workshops, and various craft-related ramblings.