Using cast iron on a glass range

Question

I currently rent, and the only problem I have with the house we're in is that it has a glass-top range. I absolutely love my cast iron cookware, and use it as often as possible.

I've heard a few reasons not to use cast iron on glass, including:

1. You can scratch the glass if you're not careful
2. It's very easy to break the glass if you drop it
3. You can melt the glass top (mentioned in linked thread)
4. It can be hard to minimize hot spots

I'm not very concerned about (1) and (2), as I've already been using cast iron on glass for years with no problems (I'm very careful when I do use it).

While researching (4) I came across (3), something I had never heard before. So, I now have a few questions:

1. Is melting the glass really plausible? This seems unlikely to me, as a quick search revealed that lowest melting point for common glass types is 1500C or higher, a temperature I have no plans to reach - but I'm not a physicist or a chemist, nor do I know what kind of glass is used to make a glass top stove.

2. Is a heat diffuser effective on a glass range? I have experienced a few hot spots on my large (12") skillet, and obviously when experimenting with my two-burner griddle. Would a heat diffuser help, especially with the two-burner (which I've all but given up with on glass for now because it's so uneven).

3. Any suggestions for safely and effectively using cast iron on a glass-top range (short of being very, very careful when moving the pans)?

Answer 1

I also have a glass-top stove at home. So far, I really like it: the heat is very even and there is good heat transfer, provided the pan makes good contact with the surface (one skillet I have has a bit of a lip, which makes it heat more slowly).

I've slapped skillets and pots full of water around on mine, and have yet to break it. I'm probably more careful than I would be on a metal range, but it seems sturdy.

But to your points:

1) There is no way cast iron could melt the glass. Iron melts lower than does glass (1200*C vs. 1500*C), so before you manage to melt your stove, your pan will be a puddle. It may, however, be possible to deform the stove top if you let an empty pan heat for some time. I don't see why this would be more of an issue with cast iron than with any other piece of cookware.

2) A heat defuser will work fine. Don't get the kind that is designed for use with gas, but anything else should work fine.

3) The burners on my stove are smaller than my skillet, so I find I need to move the skillet around to heat the edges. Also, flat-bottomed pans and pots seem to be much more effective on the flat glass top, as conduction seems more effective than radiation here. I polish the bottoms of my pots to get better heat transfer, although this is just me being anal.

Also: cast iron can't scratch glass. Glass is much harder than iron (see this wikipedia article), glass having a 6-7 on the Mohs scale, iron having a 4.

Answer 2

Regarding (3) melting glass top:

• I have, unfortunately, successfully melted a glass top range to a piece of cookware.

However, it was not with cast iron; it was with a powder-coated iron teapot. I sat down to boil some water, walked away, and forgot about it. The teapot spout did not sound, and the water boiled out of the pot. It sat on there probably 30 minutes without my attendance. When I finally remembered, I turned off the burner and tried to remove the teapot. The teapot had fused its powder-coated ceramic layer to the rangetop. When I removed the teapot, a piece of the rangetop came with it. It was a piece of about 0.5" diameter.

Based on my experience with this, I doubt a cast iron would fuse to the rangetop. It's the glass-like coating that may fuse (but not melt)

Answer 3

The idea that cast iron can somehow melt the glass range is just wrong. The cast iron can't get any hotter than the range surface itself can get. If the cast iron could melt the glass, then that means the range could melt itself.

I've only used a glass range at friend's houses, but they didn't seem particularly fragile. As long as you aren't hulk smashing your pans into the glass, it's pretty hard to break.

I have no experience with heat diffusers.

Answer 4

Cast iron Brinnel Hardness ranges from 110 for ductile types, up through 230 MAXIMUM for your gray iron pots, up to 440 for some more exotic cast iron alloys. Tempered Glass, such as your stove top, starts at a hardness rating of 1550 hb and goes up from there. TRY to use your cast iron skillet to scratch a piece of common or tempered glass. Use some tool steel such as a hardened steel razor scraper blade to try to scratch or cut it (hardness around 400~600. Use some abrasive steel wool or that razor to scrape your stove clean. You WON'T SCRATCH IT! YOU CAN'T!

DO NOT drop your cast iron on the glass repeatedly. If you do, eventually the same thing will happen as would happen with any other stove: You will damage it, and you will go to the hospital to be treated for you scalded body when the stuff hits the fan so to speak.

Cookware manufacturers, stove manufacturers, and cooking magazine editors are all eating out of the same money bucket. If they can do some risk management at the same time as promoting an idea that your 50 year old cast iron needs updating, they will. No lobbiest necessary, CEO #1 calls CEO #2 and the idea gets published and perpetuated.

I know, science is meaningless. It can be used to prove ANYTHING! :P

Have a nice dinner everyone, and have fun cooking it 1

Answer 5

As Auchtung said, the "melting" of a glass stove is actually when the coating of an enamel coated-pot/pan fuses to the stove top. The metal/iron does not appear to be able to do that. It appears this enamel fusing happens when you overheat the cookware, or also can happen (no anecdotes found about this yet) if you put hot enamel-coated cookware onto the cold stovetop, say right out of the oven (according to our Sur La Table enamel-coated cast-iron cookware's instruction manual). (Sorry, can't find this manual online right now.)

Otherwise, we have used cast iron, Le Creuset (with rough metal bottom) and ceramic coated cookware on our glass stovetop (Magic Chef) for three years now without issue. Since it's also a rental unit, the stove top was already 'scratched' - just on the rings over the burners - this looks like normal wear & tear to me, and I wouldn't consider the scratches even too unsightly. Our pots/pans are slid around the range routinely (to remove them from teh burner), and haven't caused any scratches that I can find. Having a large flat surface & repeatable control over temperature still makes me think I would install one of these instead of a Gas stove if I had the choice.

It's not like you end up with a giant scratch from one end of the surface to the other because of your cookware. But it seems you should be careful with porcelain-coated cookware. If I do have to take porcelain-coated cookware out of the oven, I place it onto a metal baking sheet on the (flat) stovetop, just in case the hot-cookware on cold-glass-top warning has some truth.

Answer 6

I melted a small spot on the edge of.my glass ceramic stove. I had taken a cast-iron roasting dish from my oven and, being distracted by conversation with my guest, neglected to get a trivet to set it on. After sitting on the stove for about 15 minutes, a spot about the size of a nickel had melted on the edge. And, yes,it'seems possible to scratch the surface, my daughter did that one night while cooking.

Answer 7

My neighbor has a glass topped stove (formerly mine, but given up as a replacement for when we almost accidentally burned down her house with a grease fire), and a few cast iron pans that she uses all the time with no problem.

I shake the pan on the glass, and haven't noticed any scratches in the about 2 years she's had it.

If you're paranoid, see the link to Lodge's website that hobodave gave in a comment -- in it, they mention that some people have reported that they've polished the bottom of their cast iron, so make them smoother, hoping it'll make them less likely to scratch.

update: my neighbors have been cooking on that stove for about 9 years, with their two main-line pans being cast iron (they have no storage place; they live on the stove) and no signs of scratching. But I also realized that if you have a properly seasoned cast iron pan (both front & back), you have seasoning touching the glass, not metal. So just make sure that you don't damage the seasoning on the bottom of the pan.

Answer 8

It is not a matter of melting the glass cook top, it is a matter of scratching or digging up the surface or even cracking it. You can't bang the heavy pot onto the glass - that is common sense. But with possible deep scratches it can make the stove top unsightly and difficult to clean.

Answer 9

Glass tops can break. My wife dropped a small corning ware lid on our 2 week old glass top from a height of less than a foot. The lid hit on the edge of the cook top and splintered off about 6 inches of one corner. The lid was fine. Not even a mark on it. We now have a new glass top. Our "new" cook top is aluminum edged. (May not help, but it makes me feel a little safer!!!).

Answer 10

My wife just melted a teapot to the glass top. When she pulled it of, it looked like about a quarter sized piece of the enamel and some of the metal was left on the stove. I turned the exhaust fan on and the burn on high and tried to scrape it with wood as another article said to do for Aluminum. That not working, i went for a metal spatula but finally had to go for a chisel. As i teased/chipped small flakes off at a time, it finally all came of, but it looks like it pitted the glass top.

Answer 11

I am a science teacher.And durig my subject matter discussed in between students i got that glasses are harder than iron.As far as i am concerned,yes glasses are harder than iron.It's another matter that glasses are brittle so they break when hammered and iron don't as because they are non brittle.But may be in real glasses are harder than iron.As glasses can produce dark scratches on iron but iron cannot do it exactly same on the glass.

Answer 12

Another issue I have seen happen on a tv cooking show was the cook took a hot lid off of a skillet and sat it over a cool burner to turn what was in the skillet, and the burner that the lid was placed over exploded due to the temperature change...I cook on a glass top stove and since I saw that happen with my own eyes I make sure my lids are never sat anywhere on my glass top stove.

Answer 13

I have had a glass cooktop for about 20 years and have used my cast iron cookware with great results all that time. I wipe the cooktop off after it cools every time I use it, which is super easy since it is smooth. I love the cooktop and have had no problems what so ever!