Purchasing a TLR in second-hand markets or auctions but not from a reliable source raises concerns about the mirror and screen's quality. After inspecting the camera, you can decide whether to keep it or do the TLR mirror and screen cleaning.
There are usually four screws on the sides of the WLF for accessing the screen and the mirror; carefully remove them, and you take out the WLF among the screen, leaving the mirror accessible in the body. Two springs hold the screen and two screws with washers hold the mirror in the most common configuration.
Take a close look at how they are installed at this point, you have to be sure you can re-install them as they were in exact same position in order to maintain the relationship with the viewing lens. Otherwise you will have to collimate the viewing lens again. It's always better to have them outside where you can work with them (using) a lens tissue.
THE MIRROR CLEANING
The back sides of these three pre-war mirrors are white or gray, whereas the back sides of post-war mirrors are silver. The two on the left are from Rolleicord, and the one on the right is from a Voigtlander Superb; all three owners decided to replace the mirrors, and I saved these for emergencies.
First, you have to clean the mirror from dust and debris using an air blower. Next, using lens cleaner fluid—I prefer Zeiss—and a cotton swab or lens tissue, gently pass them over one side of the mirror. This will reveal how good or bad the mirror is. Lastly, using a lens tissue, remove any remaining moisture while slowly moving up and down the area you are testing.
The tests on the Rolleicord mirrors passed successfully, as can be seen in the images above. The mirrors can be cleaned in the same way, always gently. Superb's mirror is beyond repair; the portion that has been cleaned is desilvering. If you don't have a spare, use it until you can get a new one, but stop cleaning it; doing so will only make it worse and you will end with a mirror as the last picture.
The screen cleaning
There are two types of screen: ground glass (frosted glass), which has one side grounded and matte; with this side, you focus, and the other side is plain glass. The corners of these screens darken.
These screens can be cleaned on both sides with lens cleaner and lens tissue, but first use an air blower or soft brush to remove dust and dirt. The mate side is softer and more prone to scratches.
Fresnel screens are the second type of screen; the image is brighter, it illuminates the screen, and the corners are much better than with the previous one. Here you will find those with a matte surface that can be used for focusing or simply as a Fresnel to enlighten, and are in addition to the standard ground glass (this setup is in some Japanese cameras).
The circular pattern of these screens makes them easily identifiable; one side has grooves and the other is plain. This type of screen is made of plastic and is extremely delicate. I only use an air compressor to clean it. The last image shows some scratches caused by attempting to clean it with a tissue; even the smallest dirt will scratch it.
WLF and body cleaning
After you have done the screen and mirror, air blow the lens/mirror compartment and the WLF from all sides before installing them in the camera. The less dust that remains after reinstalling the mirror and closing it with the WLF, the better.
The outside of the screen requires cleaning very rarely after this procedure. Only after vacation when sand can get into the WLF, snow melting can leave some marks, and a variety of other situations I'm not aware of. First, air (blow) the dirt away; second, depending on the type of screen, you can use a lens tissue.
I might have left some parts of different procedures out, but this is how I do it. So far, all is well. If you'd like to share how you do the TLR mirror and screen cleaning or have any questions, please leave a comment.
Thank you for reading.
Alex.
