Jeepers, it’s sweeping glass.
But it's not. It's getting spiders nests out of lower sash corners- where the upper sash runners prevent you from passing the stock further than 10mm over both sides. Xtremes fail miserably here. It's getting that top frame clean of any and all contamination where there's only a 10mm gap between it and the brick, stone timber frame. It's getting into the side sash runners to remove all the spiders, webs, flies etc. It's the 'effective' coverage of a given brush to determine how many passes are required per any given situation. It's the 'wet' weight of the brush which will determine the compromise between ease of use and efficacy. It's so many things, that should be so simple, but somehow have become so over complicated thus we now have a huge, over glutinous range of options that none of them seem to satisfy more than one or two specific requirements, or excel at anything that doesn't create a more negative side effect, resulting in a van loaded with £300 worth of brushes to deal with what one, maybe two at most, well designed brushes could easily achieve.
It should/could almost be as simple as 'sweeping glass' but the industry seems determined to bow to a minority and solve problems that don't exist. Instead of moving forward in a more positive, effective direction.
Rant over!😎👌🙂