From time to time, I reach into the proverbial "Everyday Cheapskate" mailbag and pull out a few of your questions to answer here. My goal is to select questions that will have wide appeal. But when the question arrives with a photo showing me the problem, that gets my attention in spades.


Dear Mary: My husband wears white undershirts, and no matter what brand or fabric content, they get gray blotches in the wash.


I typically use nonchlorine bleach and fabric softener, but I recently stopped those additions, and that didn't help. I use high-efficiency detergent. The washer is set for "whites" and the dryer to "cottons." I changed detergent brands and switched from powder to liquid, but the blotches still appear.


I wash my white T-shirts in the same load as his undershirts, and mine come out fine. I am including a photo from this last load of laundry so you can see this problem.


Any suggestions on why these blotches appear, how to remove existing ones and how to avoid them in the future will be very much appreciated! — Mona


Dear Mona: The pattern and location of the stains in your photo lead me to believe this is not a detergent problem. The culprit here is most likely perspiration. My best guess is that these blotches are caused by a reaction between urea, a broken-down protein, and salts found in human perspiration, which occurs in varying degrees from one person to another.


Yellowish armpit stains in white T-shirts are a sign of the same thing — sweat that has interacted with antiperspirant ingredients, causing those stains to show up yellow.


If you've been washing these shirts in chlorine bleach in an attempt to remove the kind of stains I see in the photo, you're only making matters worse. But don't fret! You have several options for how to remove these stains and avoid new ones in the future.


Lemon Juice


Before washing, combine equal parts lemon juice and water, and scrub until the stain is gone.


White Vinegar


Add 2 tablespoons of white vinegar to 1 cup of water, and apply to the stain. Let it sit for 30 minutes before washing.


Salt


Add 1 tablespoon of table salt to 1 cup of water. Sponge the solution into the stain until it's completely gone. Launder as usual.


Baking Soda


Combine 4 tablespoons of baking soda and 1/4 cup of water. Dab on the stain until it's gone, and then wash.


Ammonia


Dilute household ammonia with an equal amount of water, and pour onto the stain. You don't need to let it sit before washing; just toss it in.


Hydrogen Peroxide


Dilute hydrogen peroxide with an equal amount of water; apply to the stain, and let sit for 30 minutes before washing. Don't use hydrogen peroxide on colors, as it does have similar properties to bleach.


Dear Mary: I hope you can help me out with this problem. Very hard water is leaving calcium deposits all over my windows. I have tried white vinegar, and that didn't help. CLR seemed to work, but only a little bit. I can't stand to look at my windows. Help! And thanks. — Rosa


Dear Rosa: Most hard water spots and buildup sits on the surface of the glass in windows and shower doors and can be easily removed using a mixture of vinegar and blue Dawn dishwashing liquid. Since neither vinegar nor CLR (calcium, lime and rust remover) have worked on your windows, this leads me to believe your situation is not typical. Most likely, you have silica stains.


Silica, which is found in all-natural water in varying degrees, has bonded with the glass in your windows over time, causing them to appear "etched." The good news is that you may be able to remove these silica stains yourself and bring your windows back to their original clean and sparkly condition, provided they have not become permanently damaged. Are you up for the challenge?


What you need to remove fine silica that has bonded with glass is hydrofluoric acid, sold as Winsol Labs Crystal Clear 550 glass clearing agent, available in quarts and gallons, starting at about $15 from CWC Supply Inc. (1-800-830-6844). Hydrofluoric acid eats silica off the glass. It takes very little of this product to loosen and dissolve those stubborn deposits. The product directions are very specific. Make sure you read the entire label before getting started.


Good luck, and please let us know how this potential solution works out for you!


Mary invites questions, comments and tips at EverydayCheapskate.com, "Ask Mary." This column will answer questions of general interest, but letters cannot be answered individually. Mary Hunt is the founder of www.EverydayCheapskate.com, a lifestyle blog, and the author of the book "Debt-Proof Living."