Part 1: Cleaning Slides
This is the most important, and most controversial step. The first thing to realize is that it’s very possible that your 35mm slides may already be ruined beyond repair. While slides were meant to last “for a lifetime,” many of them are actually into their second or third life. Even the newest slides have still spent two decades collecting dust and moisture.
The first, and most essential piece of cleaning equipment is a MicroFiber cloth. Use this to light brush dust and dirt off the slides. Do not scrub the slides as it can damage them if there is any abrasive materials such as microscopic dust on the slide.
Some people recommend using rubbing alcohol also. If rubbing alcohol is used, make sure to use as low as a water content as possible. The water can stain the slides or worse work itself up under the cardboard and cause further issues.
Another useful tool is canned air, or much better, the Rocket Air Blaster. Use the microfiber cloth to break up the caked on dust, and then use the canned air or Rocket to clear the dust away. Note that if you are using canned air, use short bursts and sweep across the slide. If it starts getting cold, or gets to the bottom of the can, it can release moisture particulars that can get on the slides. The Rocket Air Blaster is superior in this case as it has a one way valve to keep dust from getting into the air stream, and it never gets cold like canned air.
If that still doesn’t work, and you feel like dissecting the slide, these instructions will help. Otherwise you will either have to live with the imperfections or you’ll need to remove them in a photo editor.
It is also possible that the imperfections, usually mold at this point, are in the slide itself. The only way to fix this is by taking the slide apart as above, or just throwing it away. Even then it’s iffy so I usually just throw it away unless the subject matter is unique.