The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Shattering glass! Careful of your steaming technique!

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Chrissi's picture
Chrissi

Shattering glass! Careful of your steaming technique!

This literally just happened to me 10 minutes ago:


 


I had made a nice sourdough boule and was going to put it in the oven per my most recent steaming technique: hot cast iron pan (I don't have a pizza stone or a cast iron pot) with an oven-safe, Ankor Hocking pyrex glass bowl inside of it, when I'm ready to bake, take them out of the oven, put the boule on the hot cast iron, spray water on it, then invert the glass bowl overtop of it to trap steam.  Into the oven it goes.


 


I liked using the bowl instead of a stainless steel pot (my only other oven-safe item that could be used for this purpose) because I can see the bread rise.  As a beginner baker, this is fascinating to me (even though I haven't got much rise yet, but that story is for another time...)


 


So While I'm spraying water on the boule in the cast iron, some of the water apparently got onto the bowl, I think, anyway 2 seconds later I had shattered glass all over my stovetop and kitchen floor.


 


There is an alternative explanation - apparently the burner I placed the bowl onto was ON.... my boyfriend forgot to turn it off after making tea.  But I don't see how that would shatter the bowl.  I think the water is the more likely culprit.


 


I think from now on I'll have to use my stainless steel pot to trap steam instead.  I can't see the bread but... I definitely don't want a repeat of this.


 


It just makes me think about how people recommend misting water inside the oven to cause steam.  I will NEVER do that again! I used to do it but found the trapping method more effective - so I stopped doing it.  But what I didn't realize was the oven door is made of glass, the light is made of glass... and when I'm spraying, all of that is heated up to about 500 degrees F.  It could do exactly the same thing my bowl just did.


 


Just wanted to share this story, and my thoughts on its repercussions.

grind's picture
grind

One Easter dinner I got a little bit of water on a hot pyrex dish filled with I can't remember and the same happened.  Good reminder.

SylviaH's picture
SylviaH

That must have been very scary.  Glad your ok!  I wouldn't ever spray any water around any sort of glass in any sort of oven enviroment...but I know you learned that the hard way..sorry for your accident and again glad your ok.  Anytime your not sure of something, this is a good place to ask questions.  If misting or spraying into the oven always cover your glass door is have one with a large towel.


Sylvia

longhorn's picture
longhorn

Ahhhh, the old shattered pyrex trick! Makes me think of Carl Sagan and "Billions and billions" of tiny little shards!


What a mess!


Water is a major enemy of hot pyrex - but the flame could have contributed by making it even more sensitive to cold.


Be careful of your oven window too for it can easily crack (and cost about $60 just for the glass).


Jay

dvuong's picture
dvuong

I've shattered my oven glass trying to steam my oven.  It was awful and quite frightening.  Luckily, one of our neighbors was throwing out their oven that was the same model as mine, so i just took the glass from theirs and used it to replace my shattered one. Saved myself $60. Never again will I make that same mistake!  I'll always put a towel over the glass.

Chrissi's picture
Chrissi

Will a towel actually help?  Because what it seems like might happen, is the mist just soaks into the towel and the wet part of the towel touches the window and..... shatter!

dvuong's picture
dvuong

After pouring water into my pan I remove the towel before closing the oven.  The towel is just there to protect any water droplets that may splatter onto the glass.  Glass will shatter because of thermal shock - the temperature of the water is much lower/higher than the glass itself.  As soon as the water hits the pan and becomes steamed in the oven, the temperature of the water has equilibrated enough to match oven and glass temperatures. 


 


I always pour hot/boiling water in the pan instead of cold water.

Chrissi's picture
Chrissi

That is what I mean - when you pour water, if it gets on the towel, it will get the towel wet which might still crack the glass?

dvuong's picture
dvuong

Well, unless you're completely saturating the towel, I don't see it being a problem.  A splatter or two shouldn't soak the towel too much where it seaps through to the other side. 


My method is to use something that has a mouth that makes pouring easy (eg a pyrex measuring cup).  I always wear an oven mitten to prevent steam burns and pour in a nice, gentle and easy stream.

dvuong's picture
dvuong

Try using a thick/heavy towel so you lessen the chance of water seaping through to the other side.  I try to be careful enough so that I don't get any major spills onto the towel.

Chuck's picture
Chuck

Even though Pyrex is labeled "oven safe", it's still glass; one should never use it near 500F.


The "spray inside the oven" technique for generating steam is risky for the reasons you mention. I'm under the impression that's a big reason why other techniques have largely superceded it. Another problem with steam is ovens with electronic controls. Nobody worried about them thirty years ago because they didn't exist. Now, if steam rises up into the controls and then condenses, it's likely to short something out, usually resulting in an oven that won't even turn on.


One alternative method of steaming which a lot of bakers really like is the "inverted pan".


Another alternative is a pan (cast iron frying pan?) full of lava rocks near the bottom of the oven. For pouring water into something like that without dripping and without burning my forearms, I made my own vessel by getting the longest sink waste metal "tailpiece" I could find at my local plumbing supply store and plugging the threaded end with the hugest cork a hardware store could sell me. I pour heated water in the open end, point it into the pan in the oven, and just tip it a little downward.

bread10's picture
bread10

I'm wondering is steam from a pan of water at the base of the oven likely to cause shattering glass, including pyrex glass or is it due to droplets of cold water hitting the hot glass from spraying which causes the shattering?

 

Also what temperature can pyrex glass dishes be safely heated to?

MisterTT's picture
MisterTT

shock that shatters glass, rocks and many other things besides. If you put the oven-safe glass bowl in the oven and heat it up, it won't shatter, but take it out and pour cold water on it -- you've got a temperature difference to the tune of 200 K, which, for glass, is probably enough to shatter the bowl.

Steam will have a temperature that is greater than 100C, so it shouldn't cause any trouble.

bread10's picture
bread10

Thanks for the reply MisterTT.

My understanding is that you could put glass bakeware such as pyrex into a hot oven from room temperature but when hot glass comes out of the oven you need to be careful or if cold water is added to the mix things get messy!? Is this correct or am I best always starting from a cold oven?

Also what temperature can pyrex glass dishes be safely heated to?

MisterTT's picture
MisterTT

IF the dish is oven-safe. Best to warm the dish up somewhat, though. We don't have Pyrex where I live and I'd not use it anyways, but that's pretty much the rule using glass dishes to bake. What you should keep in mind is that glass bakeware is not really intended for baking bread.

However, the lid of my elongated DO is made of glass and it stood up to what my oven says is 250 C with no problems.