There’s a nearly 200-year-old art form that uses sun as paint, and you can easily do it at home. You may not have heard of it, but cyanotype printing is so popular among photographers and crafters that there’s a whole day dedicated to it: World Cyanotype Day, which is celebrated the last Saturday of September every year.

Cyanotype originated as a form of photography in 1842 that uses ammonium iron(III) citrate + potassium ferricyanide to turn a material into a beautiful shade of Prussian blue when it is exposed to UV light (aka the sun).

By coating a piece of paper or other material in a cyanotype solution and then only exposing parts of that material to the sun, you can create monochromatic works of art using the sun itself.

It’s surprisingly easy and definitely something you can do at home as a unique craft (and as a chemistry experiment).

What you need

Here’s your shopping list for a cyanotype printing project:

• Cyanotype chemical kit, which you can get online or from a local craft store
• Watercolor or printmaking paper, though you can also use cotton for fabric prints
• A clipboard
• At least one extra clip
• Clear acrylic sheets

Gloves and an apron are also a good idea, especially if you're clumsy (like me) to prevent staining your hands and clothes.

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Where it gets fun is when you start thinking about what you want your prints to look like, because that’s when you get to be a little more creative.

The easiest option is to go on a scavenger hunt for materials that you can layer on your print to create interesting silhouettes. 

The opportunities here are endless. Fresh picked flowers, doilies and lace, beads… truly, the world is your oyster (you could even use an oyster shell).

What matters when you’re picking things is the object’s shadow. The overall shape and if it is at all transparent will impact the design it leaves behind on your cyanotype.

If you want to get a little more precise in your design, you can use transparent printer paper (available at office-supply stores) and either draw a design onto the transparent film or print out a grayscale design.

Printers print the color gray by using less ink, so anything gray in your print will allow some light through, but not as much as the transparent areas with no ink, letting you create gradients in your design.

Remember - the way cyanotype works is the parts of the paper exposed to the sun will turn blue, so anything black on the sheet with your design will be white in the final print. We did an example of this with the Weather Buddies (the reaction emojis at the bottom of our articles).

If you want an accurate representation of your design, you need to create a negative of your design, which basically means anything that should be white is black and anything that should be black is white.

In the case of our Weather Buddies, if we want the eyes to be dark in our final product, the design needs to have white eyes.

The printing process

Once you have your materials, it’s time to start printing.

Step 1: Unleash your inner chemist

Start by preparing the cyanotype solution, following the instructions on your cyanotype chemical kit. A kit includes two bottles for your two stock solutions, and you may need to prepare them in advance by adding water to the bottles at least 24 hours before you start the printing process.

The stock solutions are shelf stable up to several years, so keep them in their separate bottles until you are ready to use them.

Mix the two solutions in a small, clean bowl with equal amounts of each. A little goes a long way, so you probably don’t need much.

Make sure you do the mixing inside! Even if you are in the shade outside, there is still enough UV light to kick off the reaction that turns the cyanotype solution blue, basically defeating the purpose of the cyanotype printing process all together.

We created a makeshift dark room by setting up behind a large curtain, protecting our work from any light from nearby windows.

Step 2: The only part that actually involves “painting” something

Using a foam brush, cover your paper with a thin coat of your cyanotype solution, which should look a little yellow.

Set this aside to dry and prepare a few more sheets, if you want to do multiple.

Step 3: It’s a layered situation

Once your paper is dry, put it on top of the clipboard (or a piece of cardboard or other firm surface you can carry outside) and layer any thin, light elements that may be blown away by wind on top.

One of your acrylic sheets goes on top next to hold everything in place while the print is being exposed outside. Carefully slide the whole kit and caboodle under the clipboard’s clip, and add any extra clips to the edges to make sure everything is pressed down securely.

If you have any 3D decorations, they can go on top of the acrylic sheet.

Step 4: Do it for the exposure

Now it’s time to expose your print to the sun. Carefully transport your assembled print outside to a nice sunny spot (or, if there’s no sun in sight, you can use a UV lamp).

On a bright, sunny day, you will see the print start to develop almost immediately, with any part of the paper exposed to the sun turning blue.

The whole exposure process could take anywhere from a few minutes on a sunny day to a few hours if it’s cloudy outside.

You’ll know it’s done because the blue will fade to gray-ish bronze color, but if you’re not sure, it’s always better to leave it out longer and overexpose your cyanotype than to underexpose.

Step 5: Who doesn’t love a nice bath at the end of the day?

Bring your print back inside to a room with all of the curtains drawn, and disassemble your clipboard and set aside all of your decorations.

Gently but thoroughly rinse the paper in cold water (the colder the better to help the blue color set!) until any traces of yellow or bronze are gone. You may need to get fresh water a few times, especially if you have multiple prints.

This is when you get to see what your finished product will look like, though you’re not quite done yet.

Step 5: Hanging it out to dry then hanging it up to shine

Letting your masterpiece air dry is the best way to do it, and it doesn’t take as long as you might think, so just be patient. As it dries, the blue will fully develop and get brighter.

Once it’s dry, you’re left only with the decision of how to display your cyanotype print. Try to find a spot without direct UV light or use a frame with UV-protective glass and a mat to keep the print from pressing directly against the glass.

Step 6: Enjoy and maybe show your masterpiece off a little

This step may be self explanatory, but it never hurts to get a reminder to take a minute to appreciate the hard work that went into creating something, especially when the project is the result of nearly 200-years of sun, chemistry and creativity.

Sara Tonks is a content meteorologist with weather.com and has a bachelor’s and a master’s degree from Georgia Tech in Earth and Atmospheric Sciences, along with a master’s degree from Unity Environmental University in Marine Science.