Comparing acetone vs naptha for old lens grease finally made sense

I spent last Saturday cleaning a sticky helicoid on a 70s Pentax and tried both solvents side by side. Acetone cut the dried grease fast but left a film that needed extra wiping. Naptha took a bit longer but broke down the gunk completely and evaporated clean. The difference showed up when I re-lubed it, the naptha cleaned threads felt smoother and no residue crept back. Anyone else have a favorite solvent for this job that they swear by?

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hunt.jana3d ago

The part about acetone leaving a film is what gets me. Did you notice that film affecting how the fresh grease behaved later, or was it just a pain while you were wiping? I've had acetone leave that weird residue on brass before, and it made me wonder if it was actually breaking down the grease or just moving it around. Naptha's slower action always felt more like a real solvent to me, but I've also seen people swear by lighter fluid for the same job. My experience has been that the prep work matters more than the solvent, so I'm curious if you tried any other cleaning steps after the naptha before you re-lubed. That smoothness you got might be from the extra wiping you did after the acetone, not the solvent itself, you know? Just something to consider, your mileage may vary.