Safe picture frame 'glass' 1

[BrianGar]

Recently I got commissioned to make a batch of high end picture frames,

The frames consist of machined aluminium and cf, the frame sides being approx 40mm x 12mm thick in a 6xxx series alloy. The frame sides are not joined at each corner, but instead the entire frame is machined from one piece of plate.

I have/am allowed 3mm for glazing.

Given that these are to be shipped internationally Im a little stuck on what type of glass to go for, or what the safety standard is concerning this. Or, if there is one.

My main concern is, the glass breaking in transit, it will be around 400mm x 300mm.
My second main concern that probably should be my first, is the end user getting injured should it fall off the wall/t.top.

I looked into some type of perspex/acrylic but Im afraid that it could feel very cheap if tapped with a finger. Car pictures in dealer show rooms spring to mind, sometimes you can see waves in the plastic, but maybe they just use too thin a plastic.

Will 'plastic' cloud over time due to uv, or scratch easily from being cleaned/dusted.

Should I just go with glass and package very well(easy done) Im still left with end user possible injury.

Maybe Im just being too cautious, all my own frames seem to have what I call 'dagger glass'(ordinary) fitted.

Opinions?

Thanks folks,

Brian,

 

[IRstuff]

well, you can't see my cart, but this site

http://elitecustomglass.com/checkout/cart/

has 1/8" clear tempered glass for $20 in the size you specified. Presumably, there are others

TTFN

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[BrianGar]

Irstuff,

Thanks, I didn't realise you could get tempered off the shelf in precut sizes. Given that Im in Ireland, I guess I should look into that more locally.

Im guessing also I could go and precut my sizes, and then send them off for tempering somewhere?

Is tempered glass harder break in the first place, or is it the same strength but shatters into small pieces?

Ideally, the less shipping to and fro I have to do with the glass the better. But I guess it wont cost much should the worst happen.


Am I right in thinking I do need it tempered? Im guessing if I polish 'normal' glass at the edges it would cut down on high energy areas where a crack may start. This wouldn't stop a stray elbow of course...

I probably should go tempered and settle at that.

Brian,

 

[IRstuff]

I'm just wondering who your customers are, that they would have that high an elbow malfunction rate where you need to worry about that. Ostensibly, these are supposed to be high-end, so that might justify their inclusion, simply so that you can add to the technical specifications,
"Frame includes a tempered glass pane for the ultimate in protecting your valuable pictures."

Although, according to this site:

http://www.wisegeek.com/what-is-tempered-glass.htm

tempered glass is more brittle than regular glass, so you might want to apply a layer of plastic.

TTFN

FAQ731-376
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[BrianGar]

Customers have kids Im sure...kids will be kids no matter what.

Saw some nasty accidents over the yrs involving glass, which Id like to try keep to a minimum.

Ill spend the eve reading up on tempered glass, I may be back...

Thanks again,

Brian,

 

[EdStainless]

How thin can you get laminated safety glass?
The catch with some of these options is that they are not super clear.
There are actually some plastics (DuPont copolymers) that are clearer to the eye than glass. I don't know where you go for them in sheet though.

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[1gibson]

I don't have specifics but I am aware of lexan with a special hard coating to prevent scratches, on racing windows for example. Searching the site should turn up some options.

Look into that if you want to make people drool over your specs.

Moral of the story: If you don't want to use plastic because it looks cheap, the obvious solution is to get really expensive plastic!

 

[EdStainless]

Some of the polymers and coating that are used in glasses lenses are very clear and hard. The lens blanks are machined from larger sheets of material, maybe that is a route.

Just as an aside. We have a wall of framed photos in our house. The sun hits them directly for a few hours a day. In two of the six the glass has turned very yellow over the last four years.
Even if you go glass make sure that you know what you are getting.

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[mcgyvr]

Cast acrylic sheet would be my #1 choice. They even have some with that "green edge" look that glass has. Like Acrylite FF (a 15" x 12" piece should cost no more that $10 USD).

http://www.tapplastics.com/shop/category.php?bid=24&

 

[EdStainless]

If you want it to look like glass there are two keys.
1. It needs a higher refractive index, this is one reason that acrylic looks like plastic.
2. A hard coating to keep the surface bright. The fine haze of scratches says cheep.

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[patprimmer]

Ed

I think you will find that acrylic actually has a about the same RI as glass, being close enough to 1.5

Regards
Pat
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[mcgyvr]

Yes Acrylite FF has an RI of 1.49

 

[BrianGar]

So we're looking towards cast acrylic as being the best option?

Thanks again,

Brian,

 

[patprimmer]

Well acrylic us exceptionally good to UV and is exceptionally clear but it still will scratch with time and is not quite so rigid as glass and while much more impact resistant than glass is still considered somewhat brittle and breaks in a brittle fashion.

It is used extensively for outdoor signs and aircraft windows and street light covers where vandals are not to much of a problem.

It is also the material of choice for very large telescope lenses due to it high RI and extreme clarity. Even it's edge colour is clear.

It is also used extensively for museum showcases where the contents need some UV protection. In this case a special UV absorbing grade is used. Inherently acrylic transmits 100% of UV hence the high resistance as no energy is absorbed to do any degradation. In Ireland Acrylic is still more likely o go under the trade name of Perspex I expect, but Oroglass, Plexiglass, Lucite and Shinkolite are other trade names. I expect there are countless others.

Cell cast acrylic gives a better surface than continuous cast or extruded sheet.

Another option is scratch resistant polycarbonate. It is nowhere near as clear as acrylic, but at 3mm appears water clear and the grades with a good UV package and a good scratch resistant coating are good enough to be used for almost all new automotive headlights. It eventually yellows but is sledge hammer proof level of impact resistant.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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[BrianGar]

Pat,

In Ireland its still called 'plastic' !!

Thanks a million for that,

Talking with a sign maker/rally car window guy Monday, I now have enough info to make me sound like I know what Im talking about,

Brian,

 

[dgallup]

Depending on what is going into these frames, a good deal of UV resistance may be desired. I'd talk to some custom framers, they usually have various grades of glass, good, better, best, based on how much it will protect the photograph/painting. I don't think shatter resistance is a high priority.

The Guild for Fine Art Care and Treatment Standards recommend a minimum UV blocking level of 97 percent for the range of 300 to 380 nm.

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[patprimmer]

You don't actually want UV resistance to protect the article displayed, you want UV blocking. Acrylic has perfect UV resistance because it transmits all UV light so none is absorbed to degrade the acrylic.

Transparent to visible light but opaque to UV normally requires additives specifically for that purpose. These additives normally have a finite life, although that may have changed with nano technology and the ability to include things like white zinc oxide t about 40 nano where it is fine enough to transmit visible, but still coarse enough to block UV.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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[MintJulep]

Lexan MRT.

http://www.sabic-ip.com/resins/DataSheet/Internet/PDF/1002002131_1002003947_1002038386_SI.pdf

Designed to cover the route maps and advertising in subway cars. If you want "plastic" that's impact resistant and scratch resistant then that's the stuff.

 

[berkshire]

Brian,
If you decide to go with glass you have all of these local companies to help you.
Polycarbonate plastic tends to craze after a few years exposure to sunlight unless it has a protective coating on it.
B.E.

http://irish-websites.com/business/glassmanufacturers/

http://www.pilkington.com/europe/uk+and+ireland/english/default.htm

http://www.wexfordvikingglass.ie/

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[berkshire]

Brian,
One thing I meant to mention was that some glass companies will sell treatable glass that is untempered, you cut it to size then send it back to them for tempering.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor