Thermal Pots vs. Slow Cookers

You have seen these two products on the market. You have known their function, what they are for in the kitchen. You have also seen many different brands. You are confused if these two kitchen must-haves have any difference.

This article is to tell you that they don’t have any difference in terms of functionality, but they do have a difference in terms of technology. Both cookware keep soup or stew hot for long periods of time, but one uses electricity and the other doesn’t. We’ll do a simple comparison (without sounding like a science lesson here) between the two. Let’s start with the slow cooker first.

The slow cooker uses electricity with a thermostat plugged into the bottom of the slow cooker to keep soup/stew warm throughout the day or for long periods of time. Since it is a thermostat, you can of course set the desired temperature to be maintained. The inner pot is using the “conventional Chinese method” to retain heat, that is, using some stone material such as ceramic or porcelain. Electricity is supplied to the thermostat and it constantly produces heat at the set temperature and this heat is constantly “transferred” to the stone inner pot from the bottom. Heat convection takes place inside the inner pot. Since the inner vessel is made of thick stone, heat loss still occurs but at a slower rate.

If you look at the inner walls of the outer pot of the slow cooker, you can see that it is a shiny surface of silver fish. This further slows the rate of heat loss using the laws of radiation. As for the top of the inner pot, the lid is usually made of a thick glass material to prevent heat loss as well.

This is how the slow cooker works and remember that it uses electricity to achieve heat retention.

Now let’s move on to the thermal pots. Simply put, it makes use of the same theory of heat transfer that you have known or learned from vacuum flasks in physics during school or elsewhere. It uses the laws of convection, conduction, and radiation of heat to help retain heat.

Heat conduction and convection are greatly reduced (but not totally as this is not possible) by means of a vacuum. Vacuum is a better insulation compared to foam. Now, on the sides or walls of the thermal cooker, there is an outer wall and an inner wall. Between these walls is emptiness. With the presence of a vacuum (okay, I’m not promising science lessons here, but it’s nice to know that a vacuum contains close to zero number of atoms), heat conduction and convection slow down considerably.

Infrared radiation is reduced by means of silver coatings (like a mirror) on the sides or walls of the outer pot. In addition, the double lids (the inner pot lid and the outer pot lid) and the insulation support at the bottom of the thermal pot help to reduce the heat loss process. With the combination of vacuum and silver coatings, it greatly reduces heat transfer by convection, conduction and radiation.

If a vacuum flask can retain both hot and cold temperatures for long periods of time under the same heat transfer theory, a thermal cooker can too.

Now that we know how thermal cookers work, we proceed to compare how different they are from slow cookers.

Electricity: the slow cooker uses it while the thermal cooker does not and therefore saves money.

Safety: The slow cooker should be on for as long as you want the soup or stew hot. The thermal pot (inner) needs only 10-15 minutes on the gas stove before it is placed in the outer pot to cook itself. Both scenarios assume you’re at work and not home to tend to the soup or stew.

Versatile: The slow cooker needs a power point at all times to function, and therefore it is not convenient to take it out for picnics or outdoor activities. Since the crock pot can self-cook the moment it comes off the gas stove, it can be taken almost anywhere for up to 8 hours.

Multifunction: The slow cooker can only work for warm purposes. The thermal cooker can be used for both hot and cold (such as using it as a cooler or storing cold drinks).

Cooking Ability: The slow cooker has a higher chance of “overcooking” compared to the thermal cooker. Since the crock pot is a much slower (and “natural”) cooking method, foods like vegetables and meat will be preserved in terms of color and tenderness. Soups in crockpots have been reported to remain clear after being left “alone” after a day’s work. This is based on real experiences from real thermal cooker users who have switched from slow cookers.

Convenience: The slow cooker must be set to the correct temperature in order for it to slow cook the soup/stew properly. The thermal cooker does not need temperature adjustments as all you have to do is leave the inner pot on the gas stove for 10-15 minutes and put it back in the outer pot.

This article has a thorough understanding of how both types of pots work and the science behind it. With these understandings, it becomes clear that the thermal cooker stands out as the most convenient and economical option to cook a nice hot soup/stew with tender meat and well colored vegetables, after a hard day’s work.