Extend the Life of Glasses resp. Spectacle Lenses

Question:

I have glasses with anti-reflection coated lenses. Now more and more areas are piling up where I can only see through clouds. Cleaning everything doesn't help. Do I have to buy new glasses, or can the glasses be saved somehow?

Answer:

In the most common case, where the glasses are made of plastic and not glass, the antireflection coating is very often the problem. It usually consists of metal oxide particles applied by electrostatic bombardment. If it is now scratched or rubbed off, the view may become blurred. In addition, the plastic deforms under the influence of heat, for example when the glasses are in the sun, and then the metal oxide particles are virtually repelled. This case can be recognized by the fact that circular areas such as moon craters are free of the anti-reflection coating. If you look at the glasses under a strong light source, e.g. under an LED torch, it looks similar as if the plastic had melted. The good news is:

This can be repaired at home for a few $/£/€/CHF.

The repair is done by removing the antireflection coating as a whole. You then have a minimally reduced anti-reflection effect, but you gain a totally clear and transparent sight. From my personal experience, you can easily do without the anti-reflection coating (it was only an option when you bought it).

Prerequisites

The lenses must be made of plastic, NOT glass! However, this is the case with the vast majority of glasses (opposing its name).

Auxiliaries

• Glass etching fluid or sulfuric acid, a minimal quantity, can be ordered in the net for about 3 €/$
• Cotton buds (cotton swaps, Q-Tips^®)
• Maybe a hand cream
• Plastic gloves or Medicinal gloves
• Any plastic base, e.g. an ice cream bucket lid or similar. Attention, porcelain or glass is not suitable.

Procedure

1. Place the glasses on the base with the outer side facing upwards
   
2. Caution, glass etchant is a strong acid. Never bring it into contact with aluminium or other uncoated metals. If you have a metal frame without coating, first cream the frame around the lenses with a hand cream. A cotton swab is quite suitable for this.
   
3. Drip a few drops of the etchant onto the outer side of the lens. It might start to smell a bit like sulfur.
   
4. Use a cotton swab to spread the drops all over the lens, especially out to the edges. There may be a white veil at times.
   
5. After 10-20 seconds the violet anti-glare layer should have dissolved and only the whitish plastic is visible everywhere. Hold it under the running water faucet and rinse off the acid. Dry the glasses.

By the way, the problems are usually only on the outer side of the lenses, rarely also on the inner. If necessary, you can do the same with the antireflection coating on the inner side.

Result

The glasses are again wonderfully transparent, as directly after the purchase. The price of this procedure is by factors cheaper than buying new lenses.

Cleaning tips

By the way: The correct treatment of the lenses extends the life span considerably. It is important to know where the scratches come from:

• Dust particles can accumulate on the lenses. On the one hand they stick to fat residue from contacts and on the other hand they are attracted by the static charge caused by rubbing during cleaning. Dust is mainly a mixture of abrasion, which is a compound of various components. Any component that is harder than the surface of the glass can cause scratches when rubbed with a cloth. It is therefore important to make the glasses dust-free before rubbing, for example by blowing a lot of air onto them with your mouth. Then breathing on the glasses with exhaled air helps to create a layer of vapour that helps the cleaning. In principle, it would be even better to clean the glasses directly under the faucet, even with the help of soap, but this is often too cumbersome and time-consuming.
  
  
• Dust particles that are dangerous for the glasses often accumulate in the cloths that are used for cleaning. One should shake them strongly before cleaning to get rid of as much as possible. Furthermore, you should either wash them frequently, with soap to get rid of the fat, or replace them completely from time to time. Microfibre cloths are very good substitutes.
  
  
• The remaining scratches stem, as already clear, from contact with other objects, for example if the glasses fall down or are set down on the lenses. There's not much you can do about that other than imagine that the glasses are like a small kitten and treat them like this (:-)