Cleaning 78s with isopropyl alcohol, ethanol, methanol ("wood alcohol") is a VERY BAD idea. The shellac dissolves in the alcohol - that's why the "sheen goes off" if you use too much. The shellac also dissolves in alkali, so alkaline cleaning agents are also out of the question. Generally, the best thing is to leave them alone unless they are filthy or mouldy - if they are, find a shower tile cleaner that says it only contains "neutral" or "non-ionic" cleaning agents, and rinse it off using pure water like you can buy for car batteries. Let the water drain off in a plate rack, and don't play them for a couple of days after washing, as the shellac may still be softened slightly.If you use alcohol you might as well give them to Spud Murphy's mother for the flowerpot treatment.