Blown window seals show up after washing
A: Insulated glass windows consist of two (or more) panes of glass separated by a spacer. The glass is adhered to the spacer with a sealant, and the space between the glass panes either has the air drawn out to create a vacuum, or it's filled with an inert gas. This “dead space” between the panes of glass is what gives the window its insulating properties.
If something happens to the sealant — it gets damaged or somehow gets a hole in it — air leaks into the formerly sealed space between the panes of glass. This is commonly called a “blown seal.” Since the vacuum or the gas between the panes is no longer present, the insulating value of the window decreases dramatically.
The other thing that happens with a blown seal is that outside air gets between the panes, and it brings moisture vapor with it. In the winter, when temperature differences between the inside and outside panes are the greatest, that moisture vapor condenses, which is why a blown seal is most readily visible during cold winter months.
However, the introduction of outside air also brings in dust, which can leave small deposits inside the window. Also, the repeated forming and dissipation of condensation can leave dirty-looking streaks on glass.
So it's entirely possible that the cleaners are telling you the truth, and it's simply not possible for them to get the glass clean. If the windows were accessible, I'd suggest you try re-cleaning at least one of them yourself to see if it's possible to get it cleaner. However, you said they're high up, so I'd suggest you call a glass company. If the seals are indeed blown, they'll be able to tell, and you'll need to have the glass replaced. If they aren't, they can tell you that, as well, and you should have the glass cleaners back out to redo the job.
Q: I love to rescue and repurpose items, and I've gotten hooked on painting projects! One question I would have (about sanding) is how do you know when you have
A: You have to be careful about getting hooked. You'll be spending all your weekends at garage sales!
Sanding is kind of an experience thing. I don't know of anyone who really likes to do it, so you kind of learn not to do any more than you really need to in order to get a good finish. You'll also get lots of opinions about the best way to sand and the best tools for the job, so all I can do is share my personal preferences.
For tools, on most of my projects I use a 5-inch random orbit sander. The random swirling motion gets the sanding done quickly while minimizing sanding marks across the wood grain. On some projects, I also use a 1/4-sheet pad sander, which is a little less aggressive. It sands in a straight-line motion, so you'll want to use it with the grain. And of course, some projects require simple hand sanding.
On bare wood, start with the heaviest grit sandpaper that's needed to remove whatever you have to remove. In other words, if the wood is really rough, you might start with 60 or 80 grit paper. If it's already fairly smooth, you might start at 120.
After that, the rule of thumb is to change grits by 150% of the prior grit. So if you started with 80, the next one would be 120 (80 x 150%), then 180, then 270 etc. You many not get those exact grits, but get close.
If you're painting the wood, 180 is typically good enough. If you're staining, you'll want a finer finish; shine a bright light across the wood and look for scratches or swirl marks, and when they're gone, you're ready to finish.
As far as the paint, some spray paints are formulated specifically for wood, some for metal, some for all materials. I would recommend talking to a good paint store rather than a home center or department store for recommendations, and maybe try a few brands until you find one you like. Practice your spraying technique on scraps of wood or cardboard.
If you really enjoy this as a hobby, consider investing a little bit of money in a paint sprayer. You'll get better results, and you'll save money in the long run over buying spray cans. Again, a good paint store can help you with the selection.