Viewfinder cleaning - which side of which mirror?

[Cortexturizer]

Hi guys, I've been getting indefinite info on the web regarding this, some people say careful which side of which mirror you clean (so that the silver covering is not removed etc), some people, like this guy here:

https://www.youtube.com/watch?v=mLhwnJyADrQ

who has some incredible videos and is very crafty, cleans everything left and right like it is nothing...

You can see how it can be confusing.


So, looking at this picture with markings on each side of each mirror - http://prntscr.com/q1uxbs

can you clear this up for me once and for all pls? which side (letters) I may clean and which one is to be left alone?

as for the cleaning solutions, I only have isopropyl alcohol 95%, would that work? or is that too harsh for this kind of task?

Cheers, many thanks in advance, loving the responses I've got on some of my other topics here.

 

[Cortexturizer]

Was this asked too many times or something? If so can you please refer me to the relevant thread pls cause I wasn't able to find it. Cheers!

 

[retinax]

Are you talking about SLRs/TLRs? There's absolutely no point in cleaning the bottom of the mirror and you have to be extremely careful cleaning the top surface. These mirrors have a silver layer on top which you might damage. If you have a lose mirror you can identify the top as showing no clearly visible reflection of the little dust specs that will be on it, while there will be a reflection of them from the bottom, as the reflective surface is further away from them.
Don't be anal about cleanliness as the mirror will be out of focus: dust will be invisible, only clean it if it's really very dirty.

 

[Cortexturizer]

My post contains a screenshot that shows exactly what I am talking about.
Please have a look.

 

[retinax]

So half-mirrors or whatever they're called, huh? My advice about identifying the coated side still applies. Avoid touching the coated side if you can. In my limited experience many of them are not as fragile as you sometimes hear, but maybe some are, or it's well-meaning exaggeration to deter heavy handed beginners. Again, only clean if it's really dirty, and work your way up the solvents. I'd start with distilled water, it removes surprisingly much more dirt than tap water.