All garments are machine washable. The majority of sweatshirts and tee shirts have the manufactures's washing instructions attached.
However, Hand-painted T-shirts and sweatshirts should be washed inside out in cold or cool water, gentle cycle, then tumble dry low.
Silk screened garment should be washed inside out in cold/cool water, gentle cycle and tumble dry low heat. If you iron them do it inside out.