Suck Before It Boils

[Johnny Pneumatic]

I was thinking about inproving stoves a few months back and I hit upon something so simple I need to know why it's not used. Vacuum. The less the air pressure the lower the temp the water has to be before it boils and thus can boil faster than water under 1 bar of pressure. Why don't stoves have a vacuum box around them and after the food is sat upon the stove the air is sucked out?

 

[geni]

I was thinking about inproving stoves a few months back and I hit upon something so simple I need to know why it's not used. Vacuum. The less the air pressure the lower the temp the water has to be before it boils and thus can boil faster than water under 1 bar of pressure. Why don't stoves have a vacuum box around them and after the food is sat upon the stove the air is sucked out?

Beaucse the water boils at a lower temprteure so it does not get as hot so cooking takes longer.

 

[anor277]

A question I can answer (I think). While it is true, as you say, that lowering the ambient pressure will reduce the boiling point, the lower temperature will not cook the food properly (which is why, I hear, that mountaineers must boil their eggs for 10 minutes to get a soft boiled egg high in the mountains).

On the other hand, pressure cookers are a standard technology; the water now boils at an elevated temperature resulting in faster cooking. I had a colleague who cooked curries in a pressure cooker - beautiful tender meat in 1/2-1 hour instead of 4-5.

 

[El Greco]

Isn't hot air necessary for a good roasting/baking anyway ?

 

[anor277]

@ el G, for roasting, baking hot air is indeed necessary. For stewing, boiling, and frying speed of cooking should be dependent on the temperature of the liquid - this is of course 100 degree for boiling water (if you don't live in Denver) and higher for an oil.

 

[RussDill]

ya, I travel up to higher altitudes every now and then to get away from the heat and see some snow (8000-9000ft elevation). The difference in temperature at which water boils is *very* noticible. Everything takes longer to cook, even cookies, since water vapor escapes sooner, and takes heat away from the cookie.