There are a few types of stains that are notoriously difficult to remove, and sometimes impossible. Here are a few of the most common:
1. Blood stains
If you don't treat a blood stain immediately, it can become set in and be very difficult to remove. You'll need to use a cold water soaked cloth or paper towel and apply pressure to the area to remove as much of the blood as possible. Once you've done that, you can try using a weak hydrogen peroxide solution or a commercial enzymatic cleaner.
2. Rust stains
Rust is another difficult stain to remove, especially if it's already set in. You'll need to use a rust remover or a strong acid like vinegar or lemon juice. Apply the solution to the stain and scrub vigorously. If the stain is still there, you can try using a rust converter which will turn the rust into a black paint-like substance that can be covered up.
3. Ink stains
Ink is one of the hardest stains to remove, especially if it's from a permanent marker. You'll need to use a commercial ink remover or rubbing alcohol. Apply the solution to the stain and blot with a clean