You already know I have an affinity for khaki pants, but have I ever mentioned that I'm also a collector of white t-shirts? I probably have 15 short sleeve and sleeveless hanging in the closet right now, and I am always buying more. That's because I like my white t-shirts to look crisp and fresh.
Have you ever noticed how whites tend to gray over time? Here's why - most white t-shirts have some amount of cotton in them. Cotton isn't naturally white but more like a tan to grayish color. With repeated washings, the optical brightness (sort of a white dye kind of thing) breaks down, and all dyed fabrics tend to fade to their natural state over time. Bleaches as well as excessive wash or drying temperatures and cycle lengths exacerbate the white cotton discoloration. Some personal products, such as deoderant, anti-perspirant, and even topical medicines can cause local or general discolorations.
What can you do? Well according to my favorite enthusiastic District Manager Mike Feudale - only a few things. First he suggests not using chlorine bleach, excessive temperatures, and lengthly cycles. He likes using color safe bleaches, well dissolved and distributed, in a hot or warm load that is paused during the wash cycle for several hours. Finally he prefers drying outside on a clothes line. (On a side note, I like doing that because I love the way clothes smell when they dry outside!)
Of course since I am better at pointing out laundry problems then solving them, I just suggest calling your local A Cleaner World if you have a stubborn white issue. Any of our folks can help you out.