The liquid ink in Sharpies is similar to the ink used in screen printing, which bleeds into fabric. Sharpie ink is semi-permanent, but to secure a design or signature on T-shirt fabric, and preserve its longevity, heat is an absolute must.
Traditional Sharpie Markers
Sharpie produces several varieties of permanent markers suitable for use on T-shirt fabric. Traditional Sharpie markers can be set into fabric and are available in an array of colors. The company also makes markers specifically for use on fabric.
Sharpie Stained Markers
Sharpie Stained markers were created to last on most fabrics. They come in eight colors, including black, blue, red, green, yellow, purple, orange and pink. The markers' fine tips are good for autographing T-shirts, and like all Sharpies, they can be set permanently using the heat method.
Sharpie Rub-a-Dub Marker
Sharpie produces a Rub-a-Dub marker that won't wash out of fabrics, even without heat. Currently the Rub-a-Dub marker is only available in black, but it's the Sharpie marker with the most permanent ink.
Set on High Heat
No matter the Sharpie marker you choose, the setting process is the same. There are a couple of ways to add the right amount of heat to set any Sharpie design. An iron set on the highest heat works well. The Sharpie design or autograph should be ironed for a few minutes. A clothes dryer set on high heat can also be used to set the ink. Place the T-shirt in the dryer for around 15 minutes. Once the ink sets, wash the T-shirt in cold water, and dry it on high heat.