Re: [Leica] Removing Lens Coating

[Dr.Alexander.Kraus@gmx.de]

> 
> >As a practicing dentist for the past 25 years, I can tell you that 
> >toothpaste not only will remove just about any lens coating, but will
> also remove a fair amount of the lens element itself. You'll have a cloudy
> lens in no time!

I don't dispute the abrasive character of toothpaste. But I can also ensure
you that I have sucessfully used toothpaste to remove an old defective
coating without getting a cloudy lens. I used a special toothpaste for senstive
teeth which contain less pumice (or finer paritcles). One time I messed a lens
up, but this was when I used a power tool for polishing. If you make a slurry
of toothpaste and some water and wipe the lens without too much pressure, it
takes quite a while untile the coating is polished of - and here we are
talking about a layer of approx. 300 nanometers. I frequently check the appearance
of the surface and as soon as the coating is gone, I stop wiping the lens
and wash the lens with water until the toothpast is completely gone. Even with
a 10x magnifier I wasn't able to see any cleaning marks or cloudy surfaces.

> >Toothpaste contains varying amounts of pumice and is very 
> >abrasive. I've seen patients over the years who are so aggressive with a 
> >toothbrush and toothpaste that they have removed tremendous amounts of 
> >tooth enamel such that the tooth has snapped in half due to 
> >toothpaste-induced erosion. Tooth enamel is far harder than any lens I've
> >ever seen. 

What you describe is the result of years of abuse and the addtional impact
of agressive chemicals (acids) that are formed in the mouth.

> >As an aside, toothpaste can remove scratches in your car's 
> >paint or clearcoat quite nicely if used in small amounts on a wet rag.

I know. Toothpaste is a perfect allround polishing aid :-)

Alex

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