Originally posted by Lev I have 99,9% IPA. Some of you guys telling me not to dillute it. Can you tell why? If nothing wrong will happen making a mixture, I'd better try 50/50 or even 70/30 concentration with clear water...
99.9% should be fine. However you're only relying on that as the solvent to remove smudges from the surface. Water is also a very powerful/useful solvent so the two combined covers a larger spectrum of things that can be removed. You have the added bonus of reducing the evaporation rate by adding water (so it doesn't dry too quickly) by adding water, too.
There is absolutely nothing wrong that can happen with making a mixture, as long as you're away from any flames (as isopropyl alcohol is flammable as should be stated on the bottle)! 50:50 is fine, 70:30 with more isopropyl is fine. Both have worked on various occasions with various lenses from various decades for me,
without any ill-effect.