Prepping Supplies for Fractal Bleach Activity

This week Frances and I have been prepping supplies and creating a lesson plan for a design challenge at University Settlement. The challenge is to use patterns and fractions to create art. Since this design challenge will be the last one for the University Settlement campers, we decided to do a fun outdoor T-shirt making activity using bleach. 

Each camper will receive a dark colored T-shirt with a large square taped off in the center. Their task is to create a fractal pattern out of masking tape within the square. A fractal is a never-ending geometric pattern that can be created by making a simple pattern and then repeating it on a smaller and smaller scale. An example would be to divide the square in half, then divide that half in half, repeating that process on each new half. Fractals are commonly found in nature as snowflakes, snail shells, plants, and lightening.


We will use an extract printing process with basic household bleach to make the patterns on the shirts. Bleach is a chemical that is commonly used to whiten or sterilize materials. Extract printing is a method of applying a design to dyed fabric by using a color-destroying agent, like bleach, to expose a white or lightened color on a the darker colored ground. In contrast, additive printing requires placing ink or paint on top of the ground. The difference between the two processes is that extract printing uses a chemical reaction to take away pigment, while additive printing uses a physical reaction to add ink or paint pigment.

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We experimented with this process outside on a hot summer day. We set up a table, taped off our fractal designs, and placed various materials on the fabric to see what patterns were possible. We experimented with strings of beads, Popsicle sticks, toothpicks, stickers, pasta shells, and tape to reject the bleach with. The next step was to spray our pattern with a mixture of bleach and water. After sitting with the bleach for a minute or so, the fabric required a three-bath system to halt the chemical process. The first bath was just water to rinse the bleach, the second was a mix of water and metabisulfite, a chemical that neutralizes the bleach, and the third was a bath of water to rinse everything away.

This is a fun end-of-camp activity that is exciting to make and lets the campers take home their artwork to wear in the future!

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