# Glass cookware question



## praties (Dec 7, 2005)

I don't know why I didn't think of this when we had Harold McGee here. :crazy: Some old recipes I have from my Mom specify that if a glass baking dish is used, to reduce the oven temp 25 degrees. Is that necessary with Pyrex cookware or have we come far enough that using the same temp for Pyrex as metal is okay?

Edited for a touch of clarity.

Praties


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## castironchef (Oct 10, 2005)

I'm no McGee, but I believe that the answer is that glass, because it's a ceramic, is a thermal insulator and does not conduct heat anywhere near as well as metal. Because it's a thermal insulator, the bottom of whatever you're baking would be cooler than if it were cooked in a metal vessel. Thus, the top would be GBD (golden brown and delicious) while the bottom would still be under-temp. By reducing the oven temperature, you're slowing down the top browning and giving the bottom a change to "catch up."


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## gonefishin (Nov 6, 2004)

Huh...I actually just watched an edition of America's Test Kitchen today where they compared several baking pans. The pans ranged from a cheap Bakers secret pan for $6.95 (which won runner-up) to a $95.00 shiny All-Clad pan (which incidently rated (and browned) the worst in their test. 

Oh...how did the Pyrex fare? At the very top of the list. It browned nearly as good as the best browning dark no-stick surface pans with the ability to use metal utensils. They also cooked evenly as well, heating up quick and retaining that heat evenly.


From their kitchen to yours  lol



*I have no affiliation with the tests that were performed...nor do I have any steak in the outcome of baking pans being bought across the world*


dan


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## phatch (Mar 29, 2002)

I've read that instruction too. 

Ovens fluctuate wildly in their temps. Cook's Illustrated has also run oven tests showing most ovens fluctuate 25-50 degrees UP and DOWN from their set temps. Because of this wild fluctuation, it probably matters very little outside of some very fussy pastries for which glass wouldn't be a desirable cooking platform anyway.

Phil


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## praties (Dec 7, 2005)

Thanks, everybody! I guess I won't fret about my Pyrex too much. And I agree with the Test Kitchen folks--it's great stuff.

Praties


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## jonk (Dec 21, 2005)

It has nothing to do with Pyrex's sensitivity to oven heat. 

Contrary to what most of us might intuitively think, most cooking in a conventional oven comes from radiant energy, not convection (the hot air) or conduction (heat transfer by touching). A metal pan reflects a lot more radiant energy than glass (though metal is a better conductor). Take a look at the recipes on brownie mixes: cooking times are usually longer for metal pans than glass pans. The clear glass lets through the oven's dominant radiant energy which is absorbed by the dark brownie dough while the metal pan reflects it. A black-finished metal pan behaves more like a glass pan as black absorbs more radiant energy. Such a pan combines good absorbtion of radiant energy and the good conductivity of metal.

Of course, you can trade-off time for temperature; hence Praties cookbook which suggests a lower temperature, rather than a shorter time, when using a glass pan in the oven.


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## bohh (Nov 8, 2007)

Hi, 

I agree with all you on what you say on this issue. But been doing research and calling test kitchens,because what i have been comming up with and if you have a box of ghirardelli brownix mix you will see what I am talking about,it says 325 oven temp. for metal or glass,but baking time for metal is less than glass. Thats when i started my checking on this issue, The test kitchen replied:"glass takes longer to bake than metal". This really is the opp. of what i been taught and what is said on this site. Being totally not understanding i went out looking for a right answer and found on web sites, one Being ABOUT.com On making brownies it says in video and ingr. list that metal pans bake faster than glass. Also a web site call CHOW OR CHOW HOUND Section there called Baked or burnt does it matter whether you use metal or glass. They say glass takes longer too, you need to add extra baking time. Very Confused on this would like to hear from any one that could help me figure out which you are suppose to go by.



Bohh


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## bohh (Nov 8, 2007)

Any ones comments or help on this matter would be appr..

Bohh


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## chefsjoy (Dec 8, 2007)

Whats your alttitude?


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## bohh (Nov 8, 2007)

I never had to change anything for alittude. It doesnt apply to me.

Bohh


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## bohh (Nov 8, 2007)

Hi,

Any suggestions on this matter?

Thanks 
Bohh


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## bohh (Nov 8, 2007)

Doesnt any one have any insight or thoughts on this?:crazy:


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## ma facon (Dec 16, 2004)

Just cook, And be happy +or- a degree or so will not be noticable. Jeeshhh:chef: Although glass in cooking tends to crack every now and then.


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## mannlicher (Jan 8, 2006)

I never change the temperature of a recipe when I use a glass baking pan or pie pan. I see no downside at all to maintaining the regular temp.


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## greyeaglem (Apr 17, 2006)

I'm confused about the whole shiny pan/black pan thing. Black absorbs _light _while light or shiny reflects it, but.... it's dark in the oven so shiny or dark would all be the same in the absence of light. You might have a light on in the oven, but that's not the heat source that cooks the food.


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## bohh (Nov 8, 2007)

thanks every one for your help.

Bohh


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