When you look in a mirror you want a clear, crisp reflection. Sometimes, however, a mirror becomes discoloured, and prevents you from being able to see a proper image.
When a mirror is discoloured, often the cause of the discolouration is the breakdown of the silver backing of the mirror. The silver backing can break down because of age, water, cleaning solvents or poor initial craftsmanship.
Determine the best way to fix the mirror by noting where the discolouration is and how extensive it is. If the mirror is an antique or very large in size, it may be best to seek the advice of a professional. If it is a smaller mirror that is discoloured in the corners, discoloured overall, or discoloured because of a scratch, you can probably fix it yourself.
Replace all or part of the mirror to fix discoloured corners. You could have a professional cut off the discoloured corners and seal the mirror with extra mirror edge sealant. You may be able to purchase mirror edge sealant yourself and reapply it if necessary.
Additionally, depending on the location of the mirror, you may want to consider moving it. For example, a mirror just over the bathroom sink may have been damaged by water getting into the corners; raising it an inch or so could prevent this from happening. Discolouration in the corners is often caused by water or cleaning solution affecting the backing of the mirror.
If the discolouration was caused by cleaning materials getting into the corners, you'll also want to alter your cleaning methods by applying the glass cleaner to a cleaning cloth and wiping the mirror, as opposed to spraying the mirror with cleaner and then wiping it.
Re-silver or replace the mirror to fix an overall discolouration. It is possible to resilver a mirror either professionally or by yourself, though if the mirror is an antique, you may be advised to leave it as is. If you wish to resilver the mirror yourself, you will need a resilvering kit and a room with plenty of ventilation.
Repair a scratch that is discolouring the mirror with toothpaste or aluminium foil. If the scratch is in the front, you can try to fill in the scratch with some toothpaste--not gel--and gently buff with a soft cloth. If the scratch is in the back, you'll need to carefully remove the mirror. If it is a very large scratch, you may again be looking at resilvering as an option. However, if it is a small scratch, you can carefully take a piece of very smooth aluminium foil and cover the scratch with it by taping it to the back of the mirror. Depending on the smoothness of the foil and the size of the scratch, this may or may not do the job.
For replacing or resilvering a mirror, be sure to call around to compare prices. You may be able to find a mirror online, which can be installed by a local contractor or handyman.
Re-silvering a mirror yourself is a potentially hazardous process, as many older mirrors contain mercury. In addition, the chemicals used are dangerous to the skin and respiratory systems if you come into direct contact with them.