Glass Man
12-23-2012, 07:48 PM
Did you know that all glass surfaces are not the same? Even if they appear to be they are not. Some are more rough than others. Some carry invisible contaminants. Whether these are organic or mineral. Others have been reacted with various silanes or other chemicals from rain repellant products. Why should we care?
Because if we are applying a hydrophobe for rain repellancy or protection such surfaces will either accept such or not. Most commercial hydrophobes these days rely on a covalent bond to work. The product uses an Si-O-Si connection. Ever wonder why products like Aquapel or Diamon-Shield use an airtight container? Because as soon as the liquid hits air it begins to react with oxygen. Which means you only have just so many minutes to apply.
If you polish a glass surface with an abrasive powder/slurry it will take on a roughness equal to the size of the particle. You know those diminishing polishing compounds you use for paint clearcoats? They use what is called a friable particle. It first grinds away the heavy and light scratches. Then the particles break up into much finer little particles that give the clear coat a smooth finish. So we can use a two step process for auto glass too. Instead of using friable particles however we go from a larger particle based slurry to a much smaller one. This is practiced when removing scratches using a wet system. When prepping a glass surface for a hydrophobe we usually only use a one step.
Now the size of the particle and the method of application is critical to the quality and the physical and chemical characteristics of the glass surface. The application of simple hydrophobes with contact angles less than 150 only require a simple polish. But a much more accurate "structuring" on both the microscopic and nanoscopic level is required if we are going to apply a superhydrophobe. This hierarchical surface is achieved in several different ways.
Seeing the invisible can be a bit tricky. You can do a quick test in a local area by fogging the glass with your breath. Of course its somewhat difficult to do this to the entire car. A fogging machine would be needed for that. If you looked at a fogged surface with one of those cheap hand held thirty power lighted microscopes from Radio Shack you would see the little water drops. Depending on the physical/chemical nature of the surface these will be bigger or smaller. When you fog the surface and look at it from a few feet you can tell what the integrity of it is. There shouldn`t be any patterns in the fog. It should be completely even.
All of this is just the beginning. There is much to learn about cleaning and structuring glass surfaces to accept superhydrophobic treatments. Or according to the more commonly used terminology, "glass coatings". This is what I will be writing about for the most part on this forum. My goal is to change the Detailing Industries way of working on glass. We should be paying more attention to surface science instead of letting product manufacturers tell us how to do our jobs. Because even though they know about the chemistry of their products (and they won`t tell us!), we know from our experience what the correct application techniques are.
Henry
henrygroverjr@gmail.com
www.glass-smart.blogspot.com (http://www.glass-smart.blogspot.com)
Because if we are applying a hydrophobe for rain repellancy or protection such surfaces will either accept such or not. Most commercial hydrophobes these days rely on a covalent bond to work. The product uses an Si-O-Si connection. Ever wonder why products like Aquapel or Diamon-Shield use an airtight container? Because as soon as the liquid hits air it begins to react with oxygen. Which means you only have just so many minutes to apply.
If you polish a glass surface with an abrasive powder/slurry it will take on a roughness equal to the size of the particle. You know those diminishing polishing compounds you use for paint clearcoats? They use what is called a friable particle. It first grinds away the heavy and light scratches. Then the particles break up into much finer little particles that give the clear coat a smooth finish. So we can use a two step process for auto glass too. Instead of using friable particles however we go from a larger particle based slurry to a much smaller one. This is practiced when removing scratches using a wet system. When prepping a glass surface for a hydrophobe we usually only use a one step.
Now the size of the particle and the method of application is critical to the quality and the physical and chemical characteristics of the glass surface. The application of simple hydrophobes with contact angles less than 150 only require a simple polish. But a much more accurate "structuring" on both the microscopic and nanoscopic level is required if we are going to apply a superhydrophobe. This hierarchical surface is achieved in several different ways.
Seeing the invisible can be a bit tricky. You can do a quick test in a local area by fogging the glass with your breath. Of course its somewhat difficult to do this to the entire car. A fogging machine would be needed for that. If you looked at a fogged surface with one of those cheap hand held thirty power lighted microscopes from Radio Shack you would see the little water drops. Depending on the physical/chemical nature of the surface these will be bigger or smaller. When you fog the surface and look at it from a few feet you can tell what the integrity of it is. There shouldn`t be any patterns in the fog. It should be completely even.
All of this is just the beginning. There is much to learn about cleaning and structuring glass surfaces to accept superhydrophobic treatments. Or according to the more commonly used terminology, "glass coatings". This is what I will be writing about for the most part on this forum. My goal is to change the Detailing Industries way of working on glass. We should be paying more attention to surface science instead of letting product manufacturers tell us how to do our jobs. Because even though they know about the chemistry of their products (and they won`t tell us!), we know from our experience what the correct application techniques are.
Henry
henrygroverjr@gmail.com
www.glass-smart.blogspot.com (http://www.glass-smart.blogspot.com)