Topping up a battery...... when is best?

G'day all,

Just thought would ask the expertise amongst us a question.

When you are topping up a standard lead acid battery with distilled water..... is it best to do this before charging.. or after?

Obviously if you check with a hydrometer, then top up, it drops as you just diluted the acid, but will it condense up again better during charge, or is it best to top up after charging?

I usually do so before a charge, but a discussion at work got me wondering

Ron