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Dear Glass Detective,
I am an importer and distributor of furniture that uses tempered glass from China. I have received increased calls over spontaneously exploding glass tabletops. What can I do to ensure, or lessen, the chance of this happening? The occurrence of this happening while someone is actually at the table scares me. So far, all reports have been when no one is in the room.
Thank you,
Mr. Smith
Dear Mr. Smith,
Let me begin by thanking you for making contact with the Glass Detective in regards to the problem you are encountering with exploding tempered glass tabletops. Specifically, you said that you are an importer and distributor of furniture products manufactured in China and that of late, you have been receiving an increasing number of calls about glass tops exploding spontaneously—meaning that they are exploding without any apparent reason. They are not being hit with something or having something dropped on them, rather, they are exploding “on their own”. You further stated that thus far no one has been reported as having been injured from this exploding glass problem but you did say that the situation “scares” you. And personally and professionally, I think I would be scared too!
While you did not identify the exact sizes of these exploding glass tops or their thicknesses, a piece of ½-inch tempered glass weighs approximately 6.5 pounds per square foot. This means that 48-inch by 48-inch tabletop glass would weigh over 100 pounds Even if the glass top were to break into small pieces as it breaks, the fact is that over 100 pounds of those broken pieces are going to fall onto something or someone. If this glass tabletop were loaded down with food, silverware, and dishes or perhaps even hot coffee or tea, real damage, and injury could occur. I really am not intending to be an alarmist or add to your concerns, but I do think your concerns need to be addressed and addressed soon.
I have seen this problem up close and personal. I was personally involved with the installation of over one hundred pieces of ½” tempered glass in an atrium glass railing project at a Chicago hotel a few years ago and after the project was completed, we started experiencing spontaneous glass breakage. Because the first few breaks occurred at night, the first thought was that they were being hit by something or someone such as the cleaning crew. No one was too concerned. Soon the rate of glass breakage increased and the glass was breaking during the night hours and during the day. When this tempered glass broke, it would explode out of the rail system and rain down into the lobby. Over a period of about eighteen months, over 20 pieces of ½” tempered railing glass exploded out of this railing system. I’m sure you can imagine the chaos this caused. We had applied a safety film to both sides of the glass railing pieces but the film was not totally successful in holding the glass together after it broke. There were a couple of injuries but fortunately, they were minor. Coincidently, this glass also had been imported.
After a fair amount of forensic analysis, it was determined that this breakage was occurring “spontaneously” due to imperfections in the glass (technically referred to as inclusions) that occur during the raw glass manufacturing process. Specifically, nickel sulfide inclusions may be developed or created when metal contaminants that are rich in nickel are accidentally mixed into the glass-melting furnaces during the time of glass processing. These metallic components can then combine with sulfur in the batch to create nickel sulfide inclusions which are the primary cause of what is commonly called spontaneous glass breakage. There are naturally other contaminants that will on rare occasions also make it into the mixing process but for the most part, these are not a problem. Believe it or not, there is even a standard (ASTM C 1036) that establishes maximum allowable levels for this inclusion situation.
The real trouble begins when glass is tempered. During tempering, these nickel sulfide inclusions tend to be altered into a state which allows them to expand as time and temperature impact the glass panel in which they are residing. This expansion can, over some period of time, create enough stress to cause the glass to break. Because it is tempered glass, when it breaks it will often explode all over the place into hundreds of small fragments. I have personally witnessed this and have seen some minor skin cuts and eye injuries caused by it. I have also served as an expert witness in a case involving this.
If you can somehow save the broken glass at the origin point of the break (and I have done this) you can then have the piece of glass, at the break origin point, examined under ultra-high magnification. Then you actually can see the nickel sulfide inclusion/stone in the glass. As an aside, historically, the thicker the glass, the more likely you are to have these tempered glass spontaneous breakage problems.
1. So now the question becomes, how do we prevent this? The somewhat bad news is that you probably cannot absolutely and permanently eliminate spontaneous breakage from occurring in tempered glass. But you can certainly greatly minimize it. First, you should only deal with high-quality manufacturers who have a reputation for quality and who have been in business for a reasonable period of time. The Glass Detective is a long-time believer in the old adage that “You get what you pay for.” It is as true with glass as it is with anything and everything else. Remember, all glass is not created (manufactured) equally!
2. There is a process known as glass heat soaking which takes tempered glass and reheats it to a level below the tempering point and then cools it under controlled conditions. Tempered glass with nickel sulfide inclusions in it will typically (or usually) break during this heat soaking procedure. In essence, this process causes the glass that will ultimately break, to break under controlled conditions before it is installed in a building or put into use as a glass tabletop or glass railing. Far better that it breaks during heat soaking than after it has been installed or while serving as someone’s kitchen table.
The heat soak process is not a 100% guarantee. It will reduce the possibility of spontaneous breakage but it cannot promise protection. It is also not free. So there is added cost to be considered. There are heat soak providers throughout North America that will gladly perform this work for you. If you need assistance in identifying suppliers for this, please reconnect with us and we can provide you with contact information. I wish you well with your future business endeavors and thank you again for contacting the Glass Detective with your question. I hope the information being provided is beneficial to you as you move forward.
What is the best glass thickness for my tabletop?
The thickness of glass will depend on your table. If you will be using the glass as a cover, then go for a ¼ inch thick glass. If you will be using the glass as a table surface, then you should go for thicker glass based on the table’s size.
In case the glass top will be used for supporting heavy items, or it is bigger than 24 inches, then choose any thickness more than ¼ inch.
Choosing between ¼, ½, and 3/8 inches mainly depends on personal preference. Thicker glass will obviously feel and look more substantial but its weight might become a concern after exceeding a certain thickness. Thicker glass becomes heavier with increasing size.
Standard glass thicknesses include:
3/6 inch- This thickness is ideal for small tables, table covers, inserts, and patio tables.
¼ inches- This is ideal for table tops and protective covers for tables.
3/8 inch- This is deal for an unsupported and heavy table top where glass is used as the sole table top.
½ inch- This thickness is the most attractive and strongest thickness available and it’s ideal for unsupported and heavy tops where the only tabletop is glass.
What are heavy glass tabletops?
These are glass tops that are ½ or 3/8 inch thick. This glass is suitable for large table tops like the ones used for patio and dining tables.
They are more durable and stronger than those with lesser thickness. Hence, they are an ideal choice for larger tables that hold heavy items such as heavy dishes.
If you want to have a frameless glass top for your patio or dining table, and the glass will be resting on the table legs directly, then you should go for heavy glass for ultra strength, safety, and durability.
Do I require using tempered for my table top?
It is recommended to use tempered glass for extra strength. This type of glass is at least five to seven times harder than annealed regular glass. It is also known as safety type of glass since in case it is hit, it breaks into little pebbles that are not dangerous like broken shards of annealed glass.
In most cases, ½ inch glass isn’t tempered when manufacturing. This is because ½ inch glass is already strong due to its thickness. However, 3/8 and ¼ inch is usually tempered to enhance its strength.
It is good to note that tempering glass doesn’t change its weight or appearance. In case you have safety concerns or have children at home, then have your glass tempered.
Why type of edges should I have for glass table covers or tops?
At Majestic Glass, we have four types of glass edging for table tops and table covers. The kind of edging to choose will mainly depend on the use of the table. Some basic edge types include:
How will I measure the table before ordering a glass top?
Check for some screws and the supports beneath the table. Start with measuring from the inner side of the supports at the top. Measure the width and length.
Then multiply the width and the length to get the tabletop’s area. Arrange for a minimum ¼ inch depth, which may change based on the kind of glass to be installed.
How will I measure a table with round corners?
If you want to get a table cover for your round table, then you will want it to match with your table. For a rounded table, measure its radius. Take a ruler or tape measure and line it to the outermost table edge.
The distance you will get from this edge to the other outermost edge across the round table will give you the radius of the table. This measurement will assist you to order for a cover that will match your rounded table.
How will I measure a table that has clipped corners?
You should take measurements of the angle of a clipped table corners to ensure that the ordered table cover will match with your table. Line up a ruler or tape measure from the outermost angled edge.
The distance you will get from this specific point to the start of the 45 degrees angle edge is the table’s clipped corner measurement. You will use this measurement to order a matching cover.
How will I prevent my glass table from getting cracked?
No matter how thick a glass top is, it can still crack. For instance, placing an extremely hot item on the glass may cause it to break. Glass is not an efficient heat conductor.
Hence, one side of the glass will heat and expand more than the other surface. It will start cooling in an uneven manner and this will make it crack.
You can avoid this by putting a thick trivet beneath hot pans, pits, and dishes when serving meals on your dining table. By doing this, your glass will be protected from cracking as a result of heat.
Which is the most appropriate cleaner for mirrors and glass?
There are several good brands available in the market. You can even make a cleaning solution at home. You will simply mix 2/3 of water with 1/3 of white vinegar.
Use a lint-free cloth or paper towel when cleaning and drying glass surfaces to ensure no streaks are left behind. A crumpled newspaper will also do the job.
For more information, visit our page on glass table tops here.
If you are looking for more details, kindly visit our website.
If you want to learn more, please visit our website How to Clean Hard Plastic Chairs.