The most important tool for the traditional window cleaner is squeegee rubber. It’s a key to a great finish. A sharp edge and firm blade will ensure water is removed from the glass first time, every time. You want a little flexibility in the blade- but not too much. So warm glass in Summer, or hot water in bucket, causes the rubber to soften. In Winter when the glass is cold, hard squeegee rubber becomes too hard. You will better off to use soft rubbers instead.