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Had an accident today.


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#1 Jan Tore Soerensen

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Posted 15 June 2016 - 03:47 PM

So, maybe someone here has experienced this before, but I really didn't expect this.

 

We put a 5k dino outside a bedroom, blasting it through the window. It was placed about 5-10cm from the window. Apparantly things got too hot, and the window broke. I call this a learning experience, but I honestly didn't expect it to happen. It definitely put a good dent in our budget. Maybe this can serve as a warning to others too.

 

 


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#2 Tyler Purcell

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Posted 15 June 2016 - 04:05 PM

You shattered the glass?

If there is too much temperature differential it will absolutely shatter. I've always made it a habit to open windows I shine light through.
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#3 Jan Tore Soerensen

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Posted 15 June 2016 - 04:09 PM

You shattered the glass?

If there is too much temperature differential it will absolutely shatter. I've always made it a habit to open windows I shine light through.

Yeah, I can see that now. It wasn't especially cold outside or inside though, but those dinos get insanely hot. Should definitely have opened the window.

 

I guess this could just be a heads up to anyone else.


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#4 David Mullen ASC

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Posted 15 June 2016 - 04:09 PM

It happens to everyone at some point. A good gaffer will usually double-check how hot a window is getting and make adjustments if it seems too hot, like using heat shield or backing off the light, etc. but sometimes when adjusting the spot-flood on a light or switching lenses in an HMI PAR, the glass can suddenly crack.

And you can't leave a window open if there is smoke being used, or the sound person complains about traffic noise, etc.

I once had a xenon outside a window and stuck my head out the window to talk to an electrician when I noticed the paint on the window frame was bubbling and melting...

When in doubt, put a 4'x4' frame of heat shield in front of the light.
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#5 Jan Tore Soerensen

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Posted 15 June 2016 - 04:13 PM

It happens to everyone at some point. A good gaffer will usually double-check how hot a window is getting and make adjustments if it seems too hot, like using heat shield or backing off the light, etc. but sometimes when adjusting the spot-flood on a light or switching lenses in an HMI PAR, the glass can suddenly crack.

And you can't leave a window open if there is smoke being used, or the sound person complains about traffic noise, etc.

I once had a xenon outside a window and stuck my head out the window to talk to an electrician when I noticed the paint on the window frame was bubbling and melting...

When in doubt, put a 4'x4' frame of heat shield in front of the light.

Good to hear. And thanks for the tips.


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#6 timHealy

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Posted 15 June 2016 - 09:07 PM

Yep, heat can crack glass. Glass is very inflexible. If one portion of the glass is cool and the other portion is getting hot and has no place to expand because of its inflexibility ... bang. Glass broken by heat is usually curved. If you can't keep your hand on a sheet of glass that a light is aimed through becasue it is hot it will crack.


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#7 Macks Fiiod

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Posted 15 June 2016 - 09:14 PM

For a second I thought you were gonna say it melted the glass. Did you take a picture of the ordeal?


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#8 aapo lettinen

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Posted 15 June 2016 - 11:55 PM

soda lime glass can only stand something like 20°C temperature difference, may vary depending on the shape and size of the glass object and may be even lower if the window frame does not allow much heat expansion. if the heat expansion is restricted you have to also wary the absolute temperature of the glass, not just temperature gradients.

for comparison, borosilicate glass can stand about 150°C temperature difference which is why most laboratory glassware is made of it (you can put a beaker to ice bath and pour boiling water into it and it should not break apart. that is absolutely not possible with normal glassware)

 

I would absolutely had expected the window to broke if the 5K was only 5-10cm from it, something like 1 - 2 meters could have been safer I think


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#9 Phil Rhodes

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Posted 16 June 2016 - 04:17 AM

I once saw this done to a very large double-glazed window in a hotel, which had the hotel's logo custom etched into it.

 

Oops.

 

P


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#10 aapo lettinen

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Posted 16 June 2016 - 06:34 AM

I once saw this done to a very large double-glazed window in a hotel, which had the hotel's logo custom etched into it.

 

Oops.

 

P

 

they surely remembered that lesson for a while  :wacko:   

 

glass thickness can also factor with the heat/temperature gradient resistance, especially with round shapes. if looking lab glass, the high temperature stuff is usually much thinner (some boiling flasks etc. can be literally paper thin) and the high vacuum stuff has much thicker walls to withstand mechanical stress but does not necessary handle open flame or other extreme situations as well )

 

If free heat expansion is allowed, glass (even normal glass) can stand hundreds of degrees °C but the general temperature difference/gradient resistance depends on glass type and shape +installation. Quartz glass (fused silica) which is used for example in tungsten and HMI bulbs can withstand well over 1000°C and rapid temperature changes because of the very low thermal expansion coefficient. Borosilicate is much cheaper and easier to use and still very well suited for for example Fresnel lenses, lab glass, incandescent bulbs, kitchenware, etc.  

 

Soda lime glass is very cheap and even easier to work with but it has much much larger thermal expansion coefficient than borosilicate or quartz and therefore can't stand large temperature differences. And as mentioned, it can easily crack even if there is no temperature gradient if the window frame etc. outer factor limits its thermal expansion and therefore creates mechanical stress to the glass even if it could otherwise handle it. because of the low gradient resistance it also has to be warmed up / cooled much slower than the better glass types so that the temperature change is as even as possible


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#11 Simon Lam

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Posted 20 June 2016 - 01:38 AM

Well, I think you're just turn on the light at full power without start from dimmer. since the full power has the high heat that cause the glass break. maybe you can try next time that make it SPOT In the light through the window and keep some distance from the glass and on at low power and increase afterwards.


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#12 Jan Tore Soerensen

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Posted 20 June 2016 - 06:22 AM

Next time I'll just move it 3 feet from the window and double the wattage.


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#13 Jay Young

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Posted 20 June 2016 - 07:29 AM

I don't mean to hijack the thread, but how exactly does one get 5k out of a dino/maxi style fixture.  I have never seen one with 5 bulbs, however I suppose you could configure one with 8 650w par36s...


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#14 Jan Tore Soerensen

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Posted 20 June 2016 - 08:50 AM

Yeah, it's an 8-light.


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#15 JD Hartman

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Posted 20 June 2016 - 07:57 PM

I don't mean to hijack the thread, but how exactly does one get 5k out of a dino/maxi style fixture.  I have never seen one with 5 bulbs, however I suppose you could configure one with 8 650w par36s...

 

I recollect that Mole made a 5 light brute, but you don't often see used ones for sale.


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#16 timHealy

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Posted 23 June 2016 - 07:17 PM

I don't mean to hijack the thread, but how exactly does one get 5k out of a dino/maxi style fixture.  I have never seen one with 5 bulbs, however I suppose you could configure one with 8 650w par36s...

 

 

There are lighting manufacturers in Europe that have lights that we do not use in the US.

 

Best

 

Tim


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