Cooking cakes on asbestos mats

Question

My mother tells me when she was young her mother would bake cakes on an asbestos mat inside a lidded electric frypan. I'd assume the practice is gone now because of the reputation of asbestos, but what was the idea behind the asbestos--a simple heat spreader?

:) The mat was inside the electric frypan. – jontyc Mar 02 '12 at 07:15 — jontyc, Mar 02 '12 at 07:15

score 6 · Accepted Answer · answered Mar 06 '12 at 16:59

Health Risks Associated with Asbestos

The reputation of asbestos is indeed well-deserved. Inhalation of asbestos fibers can cause a wide range of potentially fatal conditions. It is unlikely that normal home use of a product that contains asbestos will expose one to asbestos fibers. However, people who work with asbestos, whether mining the raw materials or processing the asbestos into finished products, are at much higher risk of lung cancer and mesothelioma than the general population.

In other words, as long as no one ground up your grandmother's asbestos mat and blew it out into the room, there is no reason to be afraid of it. However, the people who mined the asbestos and the people who formed it into a mat at the factory may have gotten very sick later in life.

Thermodynamic Properties of Asbestos

Specific Heat Capacity

The reason why asbestos was a good choice for your grandmother's baking rig, other than the fact it wouldn't catch fire, is that it has a high specific heat. Specific heat is essentially a measure of how much energy it takes to raise the temperature of a given material.

Other consequences of a high specific heat are that the material will both heat evenly and loose temperature slowly. Water, for example, has a very high heat capacity. So, water takes a relatively long time to heat up, heats evenly, and cools down slowly. Of course, you can't make a baking mat out of water....

Looking at a table of specific heat capacities of various materials, we can see that the specific heat capacity of asbestos is only about one quarter that of water, but is more that twice the heat capacity of iron. If you made a mat out of iron, it would have to mass more than twice as much as the asbestos mat to have an equal heat capacity.

However, heat capacity is not the whole story.

Thermal Conduction

Thermal conduction is the transfer of heat between two objects that are in contact with each other. For example, cast iron transfers its heat to what it touches about 400 times faster than asbestos mill board. So, an iron mat would not work well at all, because it would, as you'd expect, burn the bottom of the cake.

Your grandmother needed a material with a high specific heat capacity, but low thermal conductivity.

Ovens

Baking cakes in a normal oven works similarly to how your grandmother baked cakes, and for the same reasons. The air in an oven also has a high specific heat capacity (about the same as asbestos), but very low thermal conductivity (about 1/6th that of asbestos).

An oven is much more expensive than an asbestos mat and an electric fry pan, and will take up a lot more space. It's just a trade-off.

There is still a reasonable health risk just using an asbestos product. Anyone having one should not use it, and should get it disposed of properly — TFD, Mar 06 '12 at 19:36
@TFD, that is [not](http://www.sciencemag.org/content/247/4940/294.short) the [scientific consensus](http://ukpmc.ac.uk/abstract/MED/3510581/reload=0;jsessionid=Scp9c78Gc9DnSTEC18e0.2), it is a fairy tale told by litigators and mass media. — Aaronut, Mar 07 '12 at 00:10
@Aaronut Great suffering batmans, an asbestos denier ;-) I live in country where you can't generally litigate, and we are getting rid of it! — TFD, Mar 07 '12 at 01:17
@TFD: Denier? Everything that Adam says is correct, and I'm not disputing it - it's extremely dangerous in high quantities and many people involved in its manufacture have been harmed. But as the reams of scientific papers indicate, quantity (and also sub-type) is key, it's not true that *any* exposure is going to harm you, any more so than a mild bleach solution is equivalent to concentrated chlorine gas. Virtually every country has demonized asbestos and is getting rid of/has gotten rid of it, but like so many things that have been banned, that is more political than rational. — Aaronut, Mar 07 '12 at 02:14

score 4 · Answer 2 · edited Mar 09 '17 at 17:30

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I found this today, clearing a house in Scotland enter image description here

edited Mar 09 '17 at 17:30

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answered Apr 24 '15 at 21:26

user35116

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Great photo. It is nice to be able to see historic equipment such as this, it is a nice reference adds character to the original question. – Chef_Code Apr 24 '15 at 23:28

score 1 · Answer 3 · answered Dec 11 '19 at 00:57

Asbestos mats prevented food from being burnt or scorched.

I have a copy of the old "Joy of Cooking" and the recipe for mincemeat calls for using an asbestos mat to prevent the delicate organ meat from being burned while the rest of the ingredients cook.

Suppose you can use a Silicon baking mat instead

score 0 · Answer 4 · answered Mar 02 '12 at 09:47

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I only googled this, just now, so there could be mistakes in my answer.

At least where I live (Western Europe), women indeed cooked on asbestos. Some properties of asbestos is that it's isolating, cheap and strong. Those properties make it excellent (if there weren't the known downsides) for cooking: it retains the heat well, it's cheap and you can use it everyday for quite a long time.

That's all I could find (for now). My guess is that the most important property is the isolating one. The heat is contained in the asbestos, which makes it energy-saving. There was also one mention of 'heating plates' from asbestos (I don't know the correct English term, but the modern version is something like this). So I think asbestos also stays warm for a long time, after having received direct heat.

answered Mar 02 '12 at 09:47

Mien

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"The heat is contained in the asbestos, which makes it energy-saving."? Asbestos is an insulator. Surely it would stop the bottom of the cake burning, while it 'baked' in the lidded fry pan? Just like a Dutch oven covered in hot embers. There is no energy saving, as the exterior of the pan is not insulated, so heat is lost to the outside air – TFD Mar 02 '12 at 09:51
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@TFD: I meant more that once it's hot, it stays hot. This would not apply for a regular dish, but perhaps it would for a cake (since they would've been baked longer). But of course, you could be correct. I'll research some more. – Mien Mar 02 '12 at 09:54
TFD's answer sounds more scientifically plausible I must say. The asbestos would heat up slightly to cook the bottom but mainly cause heat have to travel up the sides of the pan and radiate into the interior, giving an oven effect. – jontyc Mar 03 '12 at 13:52