Check out these pics. This is an example of first surface reflective glass that was destroyed by hydrofluoric acid and then was covered by more hard water spots over the years. I don’t even think the owners of the building know what it is. You will notice the broken black haze in the center. Also you can see the spots. And in one of the pics you can see the heavy build up of deposits at the bottom right corner. Has anyone ever seen anything like this out there? The REAL scary thing is that someone can come through and use HF on a window like this without doing any apparent damage. But the integrity of the reflective coating has been degraded. So that when a professional glass restoration company attempts to remove the newly formed spots with a light polishing compound/slurry;…the reflective coating will come of in patches. They show up as black splotches. Or small holes.
I will have to tell you in private one of these days about a very famous building that was destroyed just like this one. The guys that did it took out one of the windows and sent it to me. This was twenty years ago. I had never seen anything like it. After doing my tinker testing on it I had to call them back and tell them they were nailed to the wall. And if you think this is bad I could tell you some real horror stories.
I have scene this etching over the many years I have been cleaning glass.
Tri-Cities, WA I was called down to restore glass on a building by the owners to restore the glass from deposit buildup.
As I saw on one window the previous cleaning company who attempted to clean the glass from its deposits off the glass had no idea they were dealing with a Blue Tin on the outside glass (like a Mirror can be in Gold, Silver etc.), and once they put HF on the glass the Tin just flushed off down the glass and was removed to were you can see on the other side of the glass.
My recommendation would be is always be testing your products and how they react to different types of glass. I always do a test showing the client what I can and can’t do. I always use bio-degradable products too…
Henry, you and I was perfecting this back in the 90’s and 00’s until I left the industry for awhile.
Thanx so much for your input. Indeed, surfaces do matter. I have thought about writing a piece on the chemistry of how HF attacks the glass matrix. But I think showing what actually happens is way more convincing and spectacular. Sometime I would like to do this at a convention. If I got permission the next one coming up in August might be close enough to drive to. Would love to meet up again with some of the oldies like yourself. And meet some of our new boys on the block.