glass table tops and safety concerns...

[Kelly Burke Makuch]

I have been making glass table tops. So far nothing larger than 20 inches. They are about 1/2 inch thick and set into, not ontop of the frames. My concern is safety. When I market these tops or tables must I include a layer of tempered glass to lay fused glass on top of or write a disclaimer or note stating thermal shock or other breakage issues that may occur? How do I protect myself as well as potential customers?
Also can these tables be used outdoors in a shady garden setting(seasonally)?
I would be greatful to any insight you masters can offer....Thanks!

[Bert Weiss]

I have been making glass table tops. So far nothing larger than 20 inches. They are about 1/2 inch thick and set into, not ontop of the frames. My concern is safety. When I market these tops or tables must I include a layer of tempered glass to lay fused glass on top of or write a disclaimer or note stating thermal shock or other breakage issues that may occur? How do I protect myself as well as potential customers?
Also can these tables be used outdoors in a shady garden setting(seasonally)?
I would be greatful to any insight you masters can offer....Thanks!

Kelly

I follow the lead of big companies in the furiniture industry and provide annealed glass table tops exposed to life on earth.

I don't approve of tempered glass tabletops as they can self destruct too easily. I would prefer a chipped table top to a pile of broken glass.

Laminating is certainly a safer way to go, but you have to deal with the exposed interlayer. Since the competition doesn't do this, neither do I.

I delivered a 77" x 28" desktop made with 2 layers of 10mm and frit sandwiched in between yesterday. I'll post pictures on the Picture board.

Bert

[Tom Fuhrman]

There are lots of companies that sell table tops that are not tempered. Your general liability insurance should cover you on it. If it were 1/4" it might be more of a problem than the thicker glass. I would put a disclaimer with the top if it were used outside. You never know what kind of environment customers will put your stuff into. you might try getting an opinion on this from some of the folks on the sandcarving discussion bulletin board.

[Kelly Burke Makuch]

Thank you for offering your wealth of knowledge. It is always appreciated - even if I'm reading another post response. Kelly

[Tim Lewis]

Just make sure your liability insurnace includes product liability and is in excess of $1 million. These days you never know. Also, it would help to check each one for stress problems and maybe even document it. I can just hear the lawyers ask that question first because it is our first responsibility.

Of course if you don't own anything (like a house or retirement fund) they probably won't sue.

[JimBolesDesigns]

There are national and international standards that should be explored. It's been a few years since I looked into this topic myself so I'm sorry that I cannot give you exact names and contact information. Try searching on 'Consumer's Union' for a start. There are also ANSI and ISO standards that I do not believe are legally binding here in the States, but much of a law suite from what I recall will focus on whether the manufacture make reasonable efforts to make a safe product. If you follow published standards that can only help your 'case'.

I would also look at "The Law (In Plain English) for Crafts People" by Leonard D. DuBoff.

That should get you started.

From my experience glass in functional items has to somehow pass a mysterious psychological issue with the buying public. Somehow glass has this dual quality in the way people react to it. People feel perfectly comfortable driving at 70 MPH surrounded by glass inches from their face and don't think twice about it. On the other hand, put art glass into items like table tops, fireplace screen, doors, etc. and you very often get comments like 'oh, that's so pretty. Won't it break?'. I found myself at shows teaching people what fused glass is, and putting on demos of how it could be made to be very strong.

In the end I got tired of it.

Hope you have better luck.

[Carol Craiglow]

Interesting story about the public's perception of glass...I was recently told that I made the short list of artists for a large public art commission and that the committee loved my work and my concept. I proposed medium-sized cast glass pieces that would be siliconed in a metal framework.

However, one of the committee members asked "What if someone was driving by and a rock hit the glass and it chipped and hurt someone?" I didn't get to defend the design before the committee, but I did point out that the same thing could happen to the ceramic mosaic that was selected. The person I was talking to said "Oh, you're right!" Oh, well.

Carol

[Bert Weiss]

Interesting story about the public's perception of glass...I was recently told that I made the short list of artists for a large public art commission and that the committee loved my work and my concept. I proposed medium-sized cast glass pieces that would be siliconed in a metal framework.

However, one of the committee members asked "What if someone was driving by and a rock hit the glass and it chipped and hurt someone?" I didn't get to defend the design before the committee, but I did point out that the same thing could happen to the ceramic mosaic that was selected. The person I was talking to said "Oh, you're right!" Oh, well.

Carol

Carol

That percpeption can work both ways. In the mareketplace glass vessels and sculpture are worth lots more money than a comparable piece made of ceramics. When you campare the work, equipment necessary, skills and costs, both mediums come up fairly close. It is the fragile nature of the material and the esoteric skills necessary to make the work that increase the value of glass.

[Cecilia Davis-Taylor]

Kelly,

I have had a 28" by 15" by 1/4" Bullseye tabletop on my open poarch for two years. It is sitting atop a metal frame with bumpons to cushion it. It has survived temperatures from freezing to 100 degrees and three rambunctious grandchildren with no apparent damage.

Cecilia

[bskirwin]

I read all the comments on this topic and was curious how the change in temperatures over the seasons would affect the glass top? Could someone explain this to me? Do you recommend that the customers take the tables inside all winter long? Thanks. barbara

[Ron Coleman]

I read all the comments on this topic and was curious how the change in temperatures over the seasons would affect the glass top? Could someone explain this to me? Do you recommend that the customers take the tables inside all winter long? Thanks. barbara

If the glass is properly annealed, outside temperatures shouldn't have any effect. Proper supports that hold the top without binding as temperature and humidity (for a wood frame) fluctuates are necessary too.

I've had a glass top patio table that's been outside for 23 years and it's survived -22 f to +106 f and sun, rain, hail and over a foot of snow. And it's got scratches too.

Ron

[Geri Comstock]

This is a good question.

Recently in my metals class, a woman approached me about a glass table top her son had. It was a float glass table top on a metal base. He put a hot pan directly on it one night. He heard that noise of glass starting to stress and break that we all know so well, but because he wasn't familiar with glass, he didn't think much of it. He went to bed. At 3 AM he was woken by an explosion. The table had exploded into hundreds of pieces, embedding themselves in the wall.

The woman asked me if this was "normal". I told her you can't put a hot pan directly on glass because of risk of thermal shock. She said she didn't know that, nor did her son.

She was very concerned because if he'd been in the room when the tabletop exploded, he would have been hurt.

I think a warning label on tabletops would be a good idea. Apparently everyone doesn't know that this can cause the top to break. You can put hot stuff on ceramic tops without problem...people don't seem to know that ceramic and glass are different.

Just my 2 cents -

Geri

[Jackie Beckman]

Geri, this reminds me of a funny story. In fact - it was my first experience with how glass "works". When I was 9 my aunt went to Sri Lanka and brought me home a batik, and she explained the process she had watched while the native women were making them. In my 9 year old mind, this sounded a lot like something I could accomplish with my broken crayons and an iron. So when my girlfriend was over one day, we decided to give it a try.

My mother had this huge beautiful glass table in the dining room, and I didn't want to get it dirty, so I covered it with newspaper before starting our project. I melted my crayons in a double boiler, painted them on the fabric, crumpled up the fabric to break up the wax, covered with more paper, and began ironing to remove the rest of the wax. (or something like that - it's been over 25 years)

Anyway, as we sat there ironing, so excited that we were almost done, we heard this ENORMOUS cracking sound. We looked around, didn't see anything wrong. (Hmm? Oh well. I wonder what that was?) On we went, ironing away, until suddenly this huge piece of glass fell right in my lap! "Oh!" I yelled, "We broke the table!" We looked at each other a minute, and not coming up with a good solution, I said, "Well, let's run away."

She agreed it was the only thing we could do. Problem one: there was about two feet of snow on the ground, and we couldn't take the plowed street, because that's the way my mother would be coming home. I lived on the golf course and we decided that was the best route of escape. Off we tramped through the snow. Problem 2: Where do you go when your 9? We opted for her house. Seemed reasonable. It took forever! The snow was up to our knees, and we were falling as we went and getting stuck. Just as we were dragging ourselves up her driveway, covered with little snow balls stuck all over us, my Mother came racing down the street like Cruella Divelle! Too funny!

And that, my friends, is how I learned about thermal shock-

[charlie holden]

If you do a google search on "glass thermal shock" you'll find several sites by float and window manufacturers explaining the relevant parameters. Mostly they warn against covering too much of the edge of the glass with trim so that it is shaded and can't heat up fast enough when the sun hits the surface of the window. They also outline recommendations about the proportion of glass covered by normal shade to that exposed to direct sunlight.

I've never known of a window breaking from thermal shock, but apparently it happens enough that they put out information about it. The key is always even heating or cooling versus uneven.

And Jackie, you were apparently scarred for life by that table experience! I would think you'ld be a metal sculptor. I once ran away because they put cheese in my scrambled eggs, so I know how this stuff can linger.

[Lani McGregor]

This is a fascinating topic. I agree with Charlie that a good place to start is with the information (there’s lots of it) available for float glass.

However, most kilnformed glass (unless created solely of float glass such as Bert is doing) is a very different beast than float. As soon as you fuse together glasses of different hues and densities you greatly increase the likelihood of thermal shock. The worst case scenario is probably a fused panel composed of an asymmetrically-placed black square (sharp angles) surrounded by a white field sitting in an east-facing window in a climate given to very cold nights and forceful sunrises.

Obviously there are no hard and fast rules here since the variables are virtually limitless. It’s a bit like firing and annealing schedules: all we can really count on are some general guidelines, supported by our knowledge of how glass behaves when exposed to hot and cold and the variants occurring in different circumstances.

- Lani

PS. We happen to live in a house filled with and surrounded by “test glassâ€

[Cheryl]

I got a glass piece as a present & hung it outside my front door on a shepherd's hook. It hung from a couple of strands of beadalon or some similar product. One day, it just shattered - found it on the ground. The hanging part was still on the hook, but the rest was in bits. I figured it was because it was below freezing that day, but...?

[Clifford Ross]

Cheryl- - Did you check out the local young boys with BB guns? Did you hear snickering from the bushes ?

[Bert Weiss]

I got a glass piece as a present & hung it outside my front door on a shepherd's hook. It hung from a couple of strands of beadalon or some similar product. One day, it just shattered - found it on the ground. The hanging part was still on the hook, but the rest was in bits. I figured it was because it was below freezing that day, but...?

Below freezing is not a factor in itself. Hot sun on a below freezing day can cause temperature gradients. Even heating or cooling are not a problem, only uneven heating or cooling.

Draperies can reflect heat unevenly and cause window glass to break. WIthout the drapery, the glass just heats up evenly and is happy.

On the other hand, a cool breeze inside a room is enough to spark internal stresses to do their nasty thing.

[jdepaula]

I just finished a table top to be used on my deck. It is 14" square, 6mm thick and composed of French Vanilla, Lt. Cyan, Emerald on an Opaline base and sits in a wrought iron stand. The table top is in full sun and gets quite warm on a sunny day but, based on what I've read here, sounds like I don't have to worry about thermal shock. Is that correct?

Also, concerned that it may be a bad idea to put an iced beverage on the table when it has been in full sun.

[Bert Weiss]

6mm is thin for a table top, but not necessarily too thin. Multicolored glass does have stresses in it caused by dis-similar glasses. If they are "compatible" those stresses will be lighter. But I wouldn't consider a piece of multi colored glass to be as strong as a 6mm piece of regular clear glass. So be careful. That said, I would put the cold drink on a coaster, just like on any other tabletop.

I live with a kilncast dining room tabletop that is 20mm thick, made with 2 layers of glass. I also have a countertop that is thicker, maybe 25mm. That one has a layer of large glass frits between 10mm layers.