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Even if your shirt says "pre-shrunk" on it, it would still be a good idea to wash it. T-shirts are also coated with a starchy material to help them lay more smoothly in the store. This starchy material can prevent paint from sticking. This will keep the spray paint from bleeding onto the back of the shirt. The newspaper or cardboard should be big enough to fit inside the shirt without stretching it. Be sure to smooth out any wrinkles of ripples. You can use a stencil meant for fabric painting, or a regular stencil. You can also make your own out of thin plastic, freezer paper, or cardstock. You can even use painter's tape to create chevron stripes! Make sure that the stencil is laying flat against the fabric. If it isn't, the paint will seep under the edges and create a blurred design. If you are using a fabric painting stencil, it will probably have a sticky back. Simply press it onto the shirt and smooth it down. If you are using a regular stencil, or if you made your own, spray the back of the stencil with repositionable adhesive spray, then press it down onto the shirt. If you are using freezer paper, simply place the stencil shiny-side-down onto the shirt, then run a clothing iron over it. Ideally, you should work outside, but if you can't, a large room with lots of open windows might do. Cover your work area with lots of newspaper, and put on some old clothes or an apron. Lastly, consider putting on a pair of plastic gloves; spray painting can get messy. If you are working indoors and start to feel lightheaded, take a break and go outside for some fresh air. Shake the can for 30 to 60 seconds first, then hold it 6 to 8 inches (15.24 to 20.32 centimeters) away from the stencil. Spray the paint on using a long, sweeping motion. Don't worry if the paint is not thick enough. You can always do another layer or two. Consider spraying the design using clear sealer first. This will give you better control over the paint and prevent it from soaking into the fabric. Be sure to let the sealer dry before applying the paint. You can speed up the drying process with a hairdryer. Once the paint is dry, spray on a second coat; you should see the paint going on thicker now. If you'd like, you can do a partial layer instead using a different color for a tie-dye effect. Be very careful when removing the stencil, as some of the paint might still be wet, especially towards the edges. Unlike with fabric paint, you can let spray paint dry before removing the stencil. This is because spray paint doesn't form a thick layer that might tearlike fabric paint does. Once the shirt is dry, you can pull the cardboard out and wear your shirt.
Wash your t-shirt to remove any shrinking. Tuck a folded up newspaper or cardboard inside the shirt. Position your stencil, and secure, if necessary. Move to a well-ventilated area and get set up. Spray the shirt. Let the paint dry for 15 minutes before doing a second coat. Let the paint dry for another 10 to 15 minutes before removing the stencil and newspaper/cardboard. Let the shirt finish drying for a few more minutes.