How to whiten a white shirt with black designs that has turned a discolored white/yellow(ish)

Question

I have a printed (black) graphic T Shirt (white) where the design has held up very well over the years. When I moved all my clothing to my new place, I noticed that many of my shirts (button up blends, cotton white t shirts, etc) started turning yellow in my new location. And when I say discolored/yellow, I mean the entire shirt(s).

(I added some white pants, an envelope, and a black/white striped scarf, for comparison.)

Maybe it was the different minerals in the tap water or that I left my closet light on all the time or something else... I have no idea.

How can I get this shirt to be whiter without screwing up the design?

Answer 1

1. Test to see if the issue is caused by iron or manganese by using a reducing agent, e.g. the sodium hydrosulfite and sodium bisulfite in a product such as Red-B-Gone or Iron Out.
   • Test an inconspicuous yellowed spot to see if it is lightened.
   • Test an inconspicuous black spot to see if it is damaged.
2. Check if the yellowing is a stain that can be removed with dilute chlorine bleach, testing inconspicuous areas as above.

Since we don't know the materials used for the fabrics, or for the inks, the responsibility to test is yours.