Window cleaning, the types of glass:
In our homes or on our commercial buildings many times the last thing we think about is the type of glass that the window is made from. This article will help to inform you of those differences, why it matters, and how to clean them.
We will also discuss briefly the reason of what causes glass to scratch.
There are basically 5 types of glass that we deal with, and those types are Annealed, Heat Strengthened, Tempered, Low- E, and Insulated Glass Units (IG Units).
Annealed Glass: This type of glass is easy to clean, and when using a razor blade (or a scraper) to remove debris, DOES NOT SCRATCH when cleaning when proper methods are used while using a scraper. Annealing is a process of slowly cooling the glass to relieve internal stresses after it was formed. This type of glass is the kind that if it breaks, will break in big shards. Much annealed glass is flat glass. Almost all flat glass made is called float glass, named for the process invented in England in the 1950s by Sir Alastair Pilkington of Pilkington Glass. His breakthrough was to pour molten glass over molten tin in a mold. The glass actually floats on the tin, smoothing out to evenly fill the form.
Heat Strengthened Glass: Heat-strengthened glass is glass that has been heat treated to induce surface compression, but not to the extent of causing it to “dice” on breaking in the manner of tempered glass. On breaking, heat-strengthened glass breaks into sharp pieces that are typically somewhat smaller than those found on breaking annealed glass, and is intermediate in strength between annealed and toughened glasses. This type of glass, when it comes to window cleaning, can have fabricating debris…which will be briefly discussed later.
Tempered Glass: This type of glass is heat strengthened four or five times stronger than annealed glass. This type of glass is also called safety glass, because of the way that it breaks. When it breaks, it does so in small pieces, just like the windows on your vehicle. It protects people from serious cuts and lacerations. Tempered glass is normally stamped or etched identifying is as such. In most cases the manufacturer of the glass has their label or brand on it as well. This type of glass, when it comes to window cleaning is also the most problematic. The reason why is because of the way that it is made. If it is made correctly, then usually there is not a problem cleaning it.
When tempered glass is made, first it is cut to the size of the window or door, whatever its to be used for. Then, the edges of that glass are sanded down so there aren’t any sharp edges on it. After that, it is washed before it is heated. Then it is super heated to 5000 degrees F, and then cooled quickly. That’s what makes it break into tiny peices.
Low-E:This type of glass was made to cool down homes and buildings. It has a film that limits UV rays from passing through. It is a coating that is applied durring the making of the glass, and another coating after the glass is made.
Insulated Glass Units: An insulated glass unit, or IG unit, is two pieces of glass separated by a spacer to allow air or gas to be sealed between the panes. These types of glass are also tempered, and unfortunately, there is no standard for stamping this glass for identification.
So what causes glass to scratch?
There are a few reasons why the glass gets scratched. Most common is carelessness on the part of the people working on or near the glass. Workers that put their tools on the glass. Wiping debris off of the glass. Painters and stucco crews trying to scrape off excess paint and stucco, even concrete, and not being trained on how to properly remove debris off of glass. Uneducated and untrained window cleaners, and finally fabricating debris.
We will talk about the issue of fabricating debris in a later article, as it is an issue that has been investigated scientifically and builders, homeowners and window cleaning personnel should be aware of the subject.
All of the above mentioned types of glass can be cleaned and cared for easily by a trained window cleaning professional, as well as an informed homeowner. Please feel free to read our articles on how to clean windows for more information, and if you have any questions please feel free to call us or email us at any time and we would be happy to talk to you.