I don’t know how safe alcohol is for the AR’s finish, but for electronics you want 99+% alcohol. You don’t want any water, and 70% is 30% water. Alcohol will evaporate before your eyes, water can linger and cause problems. High purity alcohol is expensive and usually purchased online from electronics supply retailers.

I would consider using water for the front panel and non-electronic things. After all, coffee is clearly soluble in water (that’s how it is brewed).

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