We’ve all seen those trucks racing down the road with their loads of glass placed on vertical racks. It’s such a common sight that we don’t even wonder why they ship standing glass.
Glass shelves used by commercial glass companies are designed to hold glass vertically and at a slight angle.
Our glass shelf is 52 “high and the bottom is 13” wider than the top. This gives us about a 14 degree angle to hold the glass.
But why is this necessary?
For one thing, with the glass resting at a slight angle, the effects of gravity help keep the glass on the shelf. If the glass is standing up and down, the weight of the glass will easily shift over the center of gravity each time the truck turns and the glass will want to fall off the truck.
But that is not all. With the glass at an angle, rainwater is less likely to seep between the panes of glass. Two things happen when water gets between the glasses. First, a water bond is formed between the two sheets, almost like a suction cup on glass. The two leaves have no air between them because it has been replaced by water and it can be quite difficult to separate them. Second, and much worse, is the possibility of the foils being “water etched”, a condition in which minerals and chemicals in the water form deposits and cause the glass to become cloudy.
The science of why we want to manipulate glass vertically instead of horizontally is quite fascinating and you can read more about it later in this article.
But first, let’s see how to best handle a work of art to harness its vertical strength.
When I need to turn a large piece of glass over, I first slide it close to the edge of the table for easy movement.
Then I slide it over the edge of the table so I can easily grab the glass. This piece is 5 feet wide and 4 feet tall. I would recommend that you have help turning a part of this size.
But being big makes for better images, so I took a risk by turning this piece upside down.
I slide the panel to the middle of the edge of the table. The upper half of the window is still supported by the table and I hold the lower half of the window up with my right hand.
I have to be careful to prevent the window from bending. I have to hold the window long enough. Too much and I pick it up and break it. Too little and I don’t support it and it cracks.
I let the center of the window rest on the edge of the table, let the bottom of the window fall off, hold it with my right hand, and gently lift the top half of the window with my left hand. This is a true balancing act and this is the time when having two people really helps.
As the window becomes vertical, the weight of the entire panel is supported by my right hand and I lift the panel above the height of the table so that I can rest it on the edge of the table. At this point the whole panel is very wobbly and my movements have to be very precise and smooth.
(I just let the paper the panel was resting on to fall off.)
While gently resting one edge of the window on the edge of the table, I can begin to rotate the panel.
The paper finally falls off completely as I carefully continue to turn the window. The piece is so large that any movement causes the entire panel to move back and forth, so I have to be careful not to break it.
Once I rotate the panel, I position myself so that I can lower the window onto the table.
I lower the panel under the table, so that I can rest the medium on the edge of the table as I did before.
I roll down the top half of the window while lifting the bottom half.
Then I push the window onto the table, ready to weld the back.
The science of why we want to manipulate glass vertically instead of horizontally is easy to understand if we remember that it is very thin.
Since glass is such a thin sheet, its shape determines much of its strength. When a double-strength (1/8 “) sheet of glass is held horizontally, the weight of the glass pulls against it. If the piece is small, say 6” square, the weight that pulls the glass is quite small compared to its Size.
If a sheet of glass is large, the weight pulling the glass will be large enough to allow the glass to bend or at least “want” to bend. This condition puts the glass in tension and “wants” to break.
(See how it leans slightly?)
Think of a sheet of paper. When you hold a sheet of paper upright, it holds up a bit easier than when held vertically. Try this: Hold an 8×10 sheet of paper with just two fingers in an upright position. It is not easy, but you can do it.
Try to hold your sheet of paper with two fingers horizontally. It doesn’t work, its weight pushes it down.
Now take a pair of scissors and cut a 2 “x 2” square from the paper. Keep it horizontal. Why doesn’t it fold? Because the pull of gravity on it is less, as is the weight of the 6 “square piece of glass.
If that same larger piece of glass is placed vertically, the weight of the glass is supported by the surrounding glass. In other words, the glass tries to stand on its own.
Now you know why we recommend that customers place a panel on the rear seat when they take it home.
I hate that this article is too long and risks boring you, but it would be a good idea to mention the safe handling of normal glass sheets.
If you have been shopping for glass for a long time, you know that sometimes when shipping a sheet of glass it may get a small break, sometimes so small that it is difficult to see.
This fracture represents a weakness in the glass that can give way at any time.
If you handle glass sheets at all times as if they have a hidden fracture that is about to give way, you will increase your safe handling of glass.
Always bring the glass up from the top of the sheet or on the sides of the sheet near the top. Suppose it could break at any time. Taking this possibility into account will ensure that you dress and act safely.
You will wear shoes that will protect your feet if the glass falls on them. You will carry the glass in such a way that if it breaks it will fall away from you, but will not fall towards other people.
And you will store the glass carefully to minimize the formation of glass fractures.
Photos accompanying this article can be viewed at http://www.betterstainedglass.com/Newsletter/Archives/2005Sept-howtohandle/sept2005howtohandle.htm