How can I safely remove lens coatings ?

[John Salim]

I have some old ( non-camera ) eyepieces, all of which were badly 'cleaned' over the years leaving deep looking lines on the coating ( not glass scratches ) which I'd like to clean off back to the glass.
If there a safe way of removing these coatings ?
They are from the mid 1980's and 'bloomed' blue ( if that helps ? )

Many thanks,
John S

 

[bernard_L]

Cerium oxide. Look for amateur telescope construction.

 

[koraks]

I have some old ( non-camera ) eyepieces, all of which were badly 'cleaned' over the years leaving deep looking lines on the coating ( not glass scratches ) which I'd like to clean off back to the glass.

Why would you want to remove the coatings? It'll only make matters worse.

 

[bernard_L]

Why would you want to remove the coatings? It'll only make matters worse.

Indeed ! (I was just replying to the OP's question)

Say, the coated surface has a 1% reflectivity (vintage coating) and the uncoated surface 3% (just numbers for a concrete argument)
So, staring at the lens in reflection, the uncoated spots reflect 3x as much light as the coated ones; +200%! Horrible!! But the lens operates in transmission. Coated surface transmits 99%, uncoated 97%. Ratio 97/99~0.98. Just a 2% decrease in transmitted light.
Yes, there is also flare to consider. But why not enjoy your lens as-is?

 

[koraks]

Say, the coated surface has a 1% reflectivity [...]

That's exactly what I was thinking of; you used this example the other day and it came to mind when I saw this question. The practical impact of the scratches will be negligible. Removing the entire coating, however, will make a difference in reflections/glare/contrast. Not to mention that there's the risk of abrasions to the lens elements, which will exacerbate any problems.