Believe it or not rust residue does build up in glass vases. This is due to the fact that oxygen combined with water gives way to oxidation. If rust finds its way to your glass vase, there is steps that you can take to remove the unsightly brown tinge.

The easy and free way would be to fill your sink with hot water. Pour a little vinegar into the sink with a few squirts of dish soap. Go ahead and completely submerge the vase in the sink and let it sit for about 20 minutes. Thereafter, drain the sink and wash with a clean towel. This process should remove most of the rust.

If however there is stubborn rust residue inside the vase, pour boxed rice into the vase to a level that covers the stubborn area completely. Then added enough vinegar in the vase so that the rice begins to float. Go ahead and swish the rice around with a rag in the vase in such a fashion that resembles the smoothing process of sandpaper. Keep in mind that the rice will not damage your vase but keep swishing till you see the rust removed.

If the two steps above don't work you can move to a more professional means of rust remover by seeking out non toxic corrosion removers that are safe. Keep in mind that not all rust removers are non toxic so you'll need to be careful in that regard. If you go seeking a rust remover from an auto body shop, it is likely going to have toxic poisons that are harmful so be sure to seek out a source where safe non toxic rust removers are the focus.