Unfortunately, you do not. The shirt is not stained, it is bleached. The only way to cover the light spots would be to re-dye the shirt. That is probably not a good idea, as it is difficult to do properly unless you've done it before.
Yes, a black light will show stains, such as on a carpet or shirt.
To remove stains from a white shirt, soak it in a mixture of water and white vinegar for a few hours, then wash it as usual with laundry detergent. For tougher stains, you can apply a paste of baking soda and water to the stained area before washing. Always check the care label on the shirt before attempting to remove stains.
Wash it with washing machine or wash it with your hand.
Apply Nail polish remover
To effectively remove tea stains from a white shirt, mix equal parts white vinegar and water, then dab the solution onto the stain. Let it sit for 15 minutes, then rinse with cold water and launder as usual. Repeat if necessary.
No, bleaching a polyester shirt is not recommended as it can damage the fabric. It is best to use alternative stain removal methods that are safe for polyester.
Different stains require different methods of removal. Most stains, however, can be removed using a stain remover like Shout. You would need to spray the remover on the stain, rub it in a little, then launder according to the manufacturer's instructions located on the label of your custom t-shirt.
The unfortunate answer is that you don't. Most stains add a color on top of a piece of clothing that can be washed away. Bleach has removed the dye that made your shirt black in the first place. You may be able to redye part of your clothes, or reclaims them as bleached out grays, but you cannot remove the bleach stain. A black majic marker has always worked for me. It may be uneven before you wash it but is well blended after.
bleach the shirt
once it goes black it never goes back
It is really difficult to remove a stain from a black shirt. Some steps should take into account are wetting a clean cloth in cool water and wring it out, filling a sink or a clean bucket with warm water and placing a bar of soap into the water for a moment to add lather, letting it be for some minutes.
To remove color stains from a white shirt, you can try soaking the stained area in a mixture of water and oxygen-based bleach, or treating it with a stain remover specifically designed for colored stains. Make sure to follow the instructions on the product label and launder the shirt according to its care label after treating the stain.