Hi all. Just curious on how often you’d change scraper blades when doing external glass on Builder’s Cleans? I’m fairly new to window cleaning and I’m finding I’m scratching glass regardless of using the scrubber frequently to lubricate 
Which type of scraper are you using?
What materials are you running across with the blade? Paint? Hardwater? Silicone? Cement? Stucco?
What soap are you using?
What type of windows? Tempered Glass? Residential Glass?
Are you hearing pitch shifts in the blade as it is drawn across the surface?
It can be a matter of angle of the blade when applying the pressure stroke. Are you picking up the blade off the glass on the return stroke? If not some debris can become lodged under the blade and drug backwards gouging the surface.
More detail can give us better idea of the situations for advice.
Hello and apologies for my delayed response.
I’m using an Unger Ninja Pro 6" scraper. Winsol Super Slip with dishwashing detergent in about 6 litres of water. Scraping paint splatter, sticker adhesive residue, sometimes concrete and render (stucco).
I’ve watched Luke’s videos relating to builder’s cleans and yes i am lifting the blade off the glass to return.
Domestic glass but i think its that Low-E glass we use often here in Australia. On this particular job I’ll have to pay to get some windows professionally polished to remediate. Definitely a learning curve and a mistake i dont want to make/pay for again.
Luckily for me the Site Supervisor is a good bloke and understanding of my skill level.
When the scratches occur, do they appear along the corner of the blade as you a performing the scraping motion, or are they developing in the middle of the blade as you are applying the pressure?
One option is to take some 250+ grit sand paper on a poly base instead of regular paper, then draw just the corner of a new blade across the grit towards you while also rotating the blade along the y-axis. Then spin the blade and make sure you do not create any metal burs. What you should end up with a a rounded blade corner that does not have metal burs built up on either side of the blade. Do the same process on the other corner. This should only take about 5 minutes and if the corners were the source of the scratches, this should remove that sharp pivot point of the corner which is what normally digs into the glass surface.
It’s hard to say because the windows are filthy both inside and out and I can really only see once both surfaces are clean. I do feel though that the scratches are being created by the blade edges. Suffice to say, I like your sandpaper idea and i know exactly what you’re saying. I’ll be trying this on my next job.
Before we close this topic off, do you have a ballpark time frame that you use to replace blades?
Thank you for devoting your time to help a fellow community member out. Greatly appreciated.
I use a 3 inch blade in a retractable handle. It uses blades that I can easily get from the builder supply stores (Lowes/Home Depot) for $3-$4 for a pack of 5. So for me to change a blade is of no real consequence monetarily. The blades are essentially the same as squeegee rubber. Some guys will change their rubber at the beginning of each day, others will wait until the edge is rubbed dull and leaves streaks. Likewise, if I know I am going to be scraping all the windows in a CCU, I will start with a new blade and do all of the exterior, then it is a judgement call on how it is performing and what I ran into. If it was nothing but light paint overspray and some adhesive or silicone, I would continue to use it inside as well. Usually a house of 20-25 windows will be enough to dull the blade.
For CCU jobs, I usually will mop the surface, single pass scrape with the razor, then soap again, and squeegee the surface dry. If there is still adhesive or silicone along the edges, I will use a dry “magic eraser” (melamine) pad and that will usually remove the softer gummy materials. Soap it again and use the #0000 steel wool followed by one last soap and squeegee.
I have a more practiced hand so if I see a paint speck or some faint mark, I can use my razor on the dry glass to get it off. In your case, I would recommend soaping just the spot and having surface lubrication for detail scraping work until you get the literal feel for it. The angle you use and the feel of the blade sliding on the glass is going to come with time and repetition. Once you find the proper feel, you will know when the razor is still working easily, or when it has become dull and is leaving material behind resulting in multiple passes which indicates a time to swap the blade.
If you notice that the blade is in anyway compromised, I would change it out. So if you see some rust or oxidation on it since the previous time you used it to scrape 2 or 3 windows and you know it is still sharp, change it anyway. Sometimes I don’t get the blade all the way dry before storing it and it will have some oxidation on it. I don’t want loose particles on my glass so I will change the blade even if it is nearly brand new.
Running into concrete and render/stucco will dull it out way faster or may cause a nick or metal bur. The best thing to do is wipe the blade after each window and quickly inspect the edge of the blade for any deformation. When in doubt change the blade.
I can’t ask for better information and guidance than this.
Thank you, thank you, thank you!!!