title_body: What is the best way to clean a refractometer?
upvoted_answer: I'm sure there are instructions on maintenance and cleaning in the refractometers manual. However with distilled water and soft towels/tissues and/or Q-tips for the edges (be careful not to scratch the prism with the plastic handle) you can get rid of all the residue. Don't use alcohol or something like that. If the oils don't come off or if it's really dirty you could use a little bit of mild detergent in the water and wipe it with distilled water at the end to get rid of any detergent residue.