Instructions on how to use a commercial thermo cooker
February 18, 2008 — thermalcookerHere are some instructions and recipes on using a thermal cooker.
http://solarcooking.wikia.com/wiki/Heat-retention_cooking
January 18, 2008 — thermalcookerHeat-retention cooking
From Solar Cooking
Heat-retention cooking (or retained-heat cooking) saves cooking fuel because after food has been heated to cooking temperature, it is placed into an insulated box where it will continue to cook until it is done. Retained-heat cooking is often introduced along with solar cooking since it further reduces the use of traditional fuels such as firewood, and the use of this method allows much more food to be cooked each day in a solar cooker. This method of cooking is also known as fireless cooking, haybox cooking, or wonder box cooking.
Using an solar box cooker as a retained-heat cooker
Rice being cooked in a heat-retention cooker
When combining retained heat and solar cooking, if food has gotten thoroughly hot in an solar box cooker (SBC), but clouds arrive before the food is finished cooking, a switch from solar to retained heat cooking should be made before the oven temperature drops below the boiling point. For large recipes this may be accomplished by simply closing the reflective lid on the pots of cooking foods. For smaller recipes, the solar oven is opened, taking care not to allow steam to escape from under the lids, pots are pushed close together along with any heated additional mass. Insulating pads or soft cushions are tucked closely around the pots and well heated mass. The SBC lid is then closed. This effectively makes the transition from solar to retained heat cooking. The cooker lid remains closed until shortly before serving time, when the food is tested. If not completely done, a very little conventional fuel will usually finish the job.Usually solar/retained heat cooking is done right where the SBC is located. However, a lightweight portable SBC can be moved temporarily indoors for its retained heat cooking time if the sun clouds over or if it rains. It may also be brought inside more or less permanently during the off season or at night and function as an insulated box for retained heat cooking. Used in this way the SBC continues to save fuel rather than simply being stored until conditions are right for solar cooking.
See Also
Related links
- Haybox how to and description
- A good external resource on this topic is BioEnergy Lists: Haybox, Retained Heat or Fireless Cookers.
- An audio interview with Mike Bridgwater about his work in combining solar cooker and heat-retention cooking in Tanzania.
- Heat Retention Cooking vs. Solar Cooking - Mike Bridgwater
- A Wikipedia article on Vacuum flask cooking
- How to make a cooking basket with banana leaves (and a basket). The top of the webpage is slightly broken, but it has good pictures and instructions and some cooking suggestions.
Demonstrations of a thermal cooker working
January 18, 2008 — thermalcookerDream-Pot Thermal Cooking (Part 1)
http://www.youtube.com/watch?v=a0tJvmuEYSs
Dream-Pot Thermal Cooking (Part 2)
http://www.youtube.com/watch?v=E5Kk3A0idJI
Dream-Pot Thermal Cooking (Part 3)
http://www.youtube.com/watch?v=eH3MjNSoais
The good folks down under at http://www.thermalcookware.com.au have added some great online cooking demonstrations to view on cooking Lamb Shanks, Thai Green Curried Chicken and Rice and Carrot Cake.
Give them a look see at: http://www.thermalcookware.com.au/main.php?mod=Dynamic&id=43
COOKING WITH RETAINED HEAT
January 18, 2008 — thermalcookerCOOKING WITH RETAINED HEAT
http://www.inforse.dk/europe/dieret/Biomass/biomass.html
In regions where much of the daily cooking involves a long simmering period (required for many beans, grains, stews and soups) the amount of fuel needed to complete the cooking process can be greatly reduced by cooking with retained heat. This is a practice of ancient origin which is still used in some parts of the world today.
In some areas a pit is dug and lined with rocks previously heated in a fire. The food to be cooked is placed in the lined pit, often covered with leaves, and the whole is covered by a mound of earth. The heat from the rocks is retained by the earth insulation, and the food cooks slowly over time.
Another version of this method consists of digging a pit and lining it with hay or another good insulating material. A pot of food which has previously been heated up to a boil is placed in the pit, covered with more hay and then earth, and allowed to cook slowly with the retained heat.
THE HAYBOX COOKER
This latter method is the direct ancestor of the Haybox Cooker, which is simply a well insulated box lined with a reflective material into which a pot of food previously brought to a boil is placed. The food is cooked in 3 to 6 hours by the heat retained in the insulated box. The insulation greatly slows the loss of conductive heat, convective heat in the surrounding air is trapped inside the box, and the shiny lining reflects the radiant heat back into the pot.
Simple haybox style cookers could be introduced along with fuel-saving cook stoves in areas where slow cooking is practised. How these boxes should be made, and from what materials, is perhaps best left to people working in each region. Ideally, of course, they should be made of inexpensive, locally available materials and should fit standard pot sizes used in the area.
BUILDING INSTRUCTIONS
There are several principles which should be kept in mind in regard to the construction of a haybox cooker:
Insulation should cover an six sides of the box (especially the bottom and lid). If one or more sides are not insulated, heat will be lost by conduction through the uninsulated sides and much efficiency will be lost.
The box should be airtight. If it is not airtight, heat will be lost through warm air escaping by convection out of the box.
The inner surfaces of the box should be of a heat reflective material (such as aluminium foil) to reflect radiant heat from the pot back to it.
A simple, lightweight haybox can be made from a 60 by 120 cm sheet of rigid foil-faced insulation and aluminium tape. Haybox cookers can also be constructed as a box-in-a-box with the intervening space filled with any good insulating material. The required thickness of the insulation will vary with how efficient it is (see below).
| Good Insulating Materials | Suggested Wall Thickness |
| Cork | 5 cm |
| Polystyrene sheets/pellets/drinking cups | 5 cm |
| Hay/straw/rushes | 10 cm |
| Sawdust/wood shavings | 10 cm |
| Wool/fur | 10 cm |
| Fiberglas/glass wool | 10 cm |
| Shredded newspaper/cardboard | 10 cm |
| Rice hulls/nut shells | 15 cm |
The inner box should have a reflective interior: aluminium foil, shiny aluminium sheeting, old printing plates, other polished sheet metal’ or silver paint will all work. The box can be wooden, or a can-in-a-can, or cardboard, or any combination; a pair of cloth bags might also work. Be inventive. Always be sure the lid is air tight.
INSTRUCTIONS FOR USE
There are some adjustments involved in cooking with haybox cookers:
Less water should be used since it is not boiled away.
Less spicing is needed since the aroma is not boiled away.
Cooking must be started earlier to give the food enough time to cook at a lower temperature than over a stove.
Haybox cookers work best for large quantities (over 4 lifers) as small amounts of food have less thermal mass and cool faster than a larger quantity. Two or more smaller amounts of food may be placed in the box to cook simultaneously.
The food should boil for several minutes before being placed in the box. This ensures that all the food is at boiling temperature, not just the water.
The boxes perform best at low altitudes where boiling temperature is highest. They should not be expected to perform as well at high altitudes. One great advantage of haybox cookers is that the cook no longer has to keep up a fire or watch or stir the pot once it’s in the box. In fact, the box should not be opened during cooking as valuable heat is lost. And finally, food will never burn in a haybox.
Thermal Cooking
January 18, 2008 — thermalcookerWelcome to my thermal cooker thermo cooking web blog where I hope to collect and share information on the methods and functions of using slow cooking for what ever need you might have.
I plan on pulling information in on haybox cookers, vacuum flask cooking, thermos and wonderboxes that use the process of an insulated container to store the heat and cook the food we eat daily or in emergency situations. Along with the how to’s and what for’s and recipes for these non-electric slow cookers.
January 18, 2008 — thermalcooker
http://www.survivalblog.com/2007/12/time_and_energy_efficient_cook.html
Time and Energy Efficient Cooking, by KBF (Dec 12 2007)
I wish to share some valuable information on my personal experiences with the use of two cooking devices which I incorporate into daily homemaking practice when I am attempting to conserve on water and on fuel usage. Both of them are extremely time and energy efficient.
The two kitchen products which have earned their weight in silver in my home are my pressure cookers, and my newest kitchen toys, which come from an old Asian origin and cooking concept, the thermo cooker pot.
I have and use several sizes of pressure cookers. I chose the pot size for use for the job I’m performing based on the fill capacity of the product I am cooking in it. The pot capacity should never be over 2/3rds full. The food is liquid pressure cooked on the basis of requiring very little water or liquid and a minimal amount is lost and released as pressurized steam, thus it cooks evenly, thoroughly, and quickly. Time savings average about one half compared to the usual on the stove top methods. Fuel savings are dependant on the time required for the recipe. I use this method for large vegetable batches, and large cuts of meat, like roast cuts or several chickens and get a finished product that is tender to cut with a fork. My very large pressure pots are mostly used for canning purposes to put up jars of volume batches of seasonal produce, meats, and jellies. Using the pressure cookers overall cuts my actual cooking and canning time by one third, compared to using the open pot boil methods. When you are putting up hundreds of jars, this time efficiency becomes necessity. I have had a few mishaps however over the years. They were character building learning experiences of what not to cook in a pressure cooker. Beans, rice, and whole grain cereals need to be constantly monitored, as the small needle outlet from which the pressurized steam escapes becomes easily clogged, and when it does you have now created a bean bomb! If you’re like me and are multitasking in or out of the household, constant sitting to a pot is not time efficient or possible. I have discovered my next favorite device as a result of this need to cook my one pot meal favorite dishes and also to simultaneously free myself to leave to do other equally important jobs. This device allows me to leave the house and come home hours later to a safe, hot cooked meal.
The thermo cooker pot is actually two pots, one (the cooking pot) is inserted into a second thermo insulated pot and is sealed with a hermetic seal lid. The pots can be found in Asian market stores, online, and from high end kitchen and industrial supply houses and are sold by numerous makers. Some makers sell their pots to other distributors who stick their retail labels on them. More expensive in this case is not necessarily a better pot. Key points of its success for your needs are to consider the following issues when searching to procure one. The pot set needs to be constructed of excellent quality stainless steel in order to maintain heat conductivity and easily clean and withstand staining. The floor of the pot must be constructed of no less than two air-insulated layers. The inner pot’s volume size needs to be one that will compromise and accommodate the majority of food dishes you normally prepare, if you desire to own just one size. Think in volumes of servings somewhere between how much soup, stew, arroz con pollo [rice and chicken], or how much hot grain cereal you make in one batch. Waste is non productive and expensive ultimately in time and money. Thermo cooker pots work on the principals of applying fast radiant energy cooking to your prepared dish by using the inner cooking pot on the stovetop. The recipe chosen must be able to be brought up to and kept to a boiling temperature for at least 5 minutes, the longer you can boil it the better. Secondly, this inner pot is covered and then immediately placed inside the slightly larger external thermo chamber pot, it is tightly sealed, and taken off the radiant source to finish the cooking process over the next hour on its own kinetic heat requiring no external fuel source. I leave mine in the warmest location in the house. The food contained inside the thermo chamber continues to cook by conductant heat for the next hour or so at a heat temperature gradient loss of kinetic energy which gradually decreases over 6 hours of time and maintains itself at a warming temperature up to 8 hours. The food will then remain warm to +/- 160 degrees up to 8 hours, this being dependant on normal external ambient room temperatures. I have tested my unit with a thermometer after 8 hours, and it made the grade in 65 degree ambient room temperature. This can be a boon to use in fuel and time conservation modes during TEOTWAWKI. It can also be used inversely chill perishable foods safely for consumption for 6 to 8 hours. Think summer mayonaise and egg based salads or cool fruit salads or transporting fresh farm pot cheeses without ice.
I have now mastered my pots usage to include making yogurt, soft goat cheeses and tofu successfully by not boiling the milk or soybean curd but by bringing it slowly up to incubation temp for the culture I am using, and then using the thermo pot to finish the process of maintaining the heat source. In the past I used an old wide mouth thermos bottle to do this method but it did not hold enough volume for my family’s consumption or barter needs. We also now wake up to fresh hot maple wheat berry cereal in the morning by preparing this before retiring for the night. I have used the thermo pot now on different stove and fuel sources, including wood burning and get pretty consistent result. I have used it even away from home to travel and on hunting trips using the butane camp stove. I have boiled the recipes required water, and dumped in our packaged dehydrated camp food, to either wake up to warm eggs and sausage or to come back from the hunt to eat a great hot meal.
I hope this info will help all the cookies create more efficiency in their survival preparations and also to help them find more enjoyment time to read JWR’s great postings and books!
Have a blessed and bountiful New Year!
January 18, 2008 — thermalcooker
The Haybox: Why Every Household Needs One
http://www.talkingleaves.org/node/142
“Revolutionary Kitchen Device Guarantees
If the above were an actual ad, it would likely provoke a few questions:
(1) Is this just a lot of hype, a quick-sell con job?
(The answer is, fortunately, no. This essential kitchen device is not a fraudulent marketing ploy but an easy-to-build item, and it actually performs as described.)
(2) If such a device exists, why doesn’t everyone have one?
(I don’t know. Everyone should have one. We live in a commercial culture where do-it-yourself ecological practices are not promoted because they don’t make anyone a fast buck or increase the GNP. More education is necessary.)
(3) How can my household or community get one?
(It’s easy: make it yourself.)
The device I’ve described is a haybox, also known as a retained-heat cooker, insulated cooker, or wonder box. Of all the sustainable technologies I’ve encountered in my years of living in community, it’s the one that is the most universally applicable and appropriate. In short, every community and household should have one–or ideally, more than one. We at Lost Valley Educational Center have five; Aprovecho Research Center (which has led the way in educating about them) has at least half a dozen; other intentional communities, urban cooperatives, co-housing and activist groups are discovering them; and some eco-pioneers are even whispering about installing hayboxes in the White House once it is recaptured from its current occupiers in 2004. Good for people, good for the earth, and good for our country, hayboxes are the essence of patriotism. In fact, only terrorists wouldn’t like them.
Hayboxes work on the simple principle that if the heat applied to food in the cooking process can be retained within that food, rather than lost to the environment, no “replacement heat” is needed to keep the food cooking. In conventional cooking, any heat applied to a pot after food reaches boiling temperatures is merely replacing heat lost to the air by the pot. In haybox cooking, food is brought to a boil on the stove, simmered for a few minutes (5 minutes for rice or other grains, 15 minutes for large dry beans or whole potatoes), then put into an insulated box, where it completes its cooking. Food will be ready in anywhere from one to one-and-a-half times the “normal” completion time, with no tending needed and no danger of burning, and will stay piping hot for many hours, allowing maximum flexibility in the cook’s and the eaters’ schedules. For grains or beans, water is reduced by one-quarter, because water is retained within the food rather than simmered away into the air (it’s important to use pots with tight-fitting lids in haybox cooking). The larger the quantity cooked, the more effective this technique is (the hotter the food will stay, for longer), because increased thermal mass holds more heat. And because most of the cooking occurs in the 180 degrees F-212 degrees F range, rather than at a constant 212 degrees , more flavor and nutrients are preserved.
As in conventional cooking, presoaking and draining beans makes them easier to cook and to digest. A few particularly long-cooking foods, such as garbanzo beans, may need reboiling part-way through the cooking process. For health reasons, meat dishes should always be reboiled before serving–but all other foods should be safe to eat straight out of the haybox. (However, don’t put a partially-eaten pot of lukewarm food back into the haybox without first reheating it, since hayboxes are not only excellent cookers but also ideal incubation chambers for yogurt and other bacteria-rich food.)
Hayboxes are easy to construct through a variety of methods. The haybox itself is any kind of insulated container that can withstand cooking temperatures and fits relatively snugly around the pot. Effective insulation materials include hay, straw, wool, feathers, cotton, rice hulls, cardboard, aluminum foil, newspaper, fiberglass, fur, rigid foam, and others. The insulation is placed between the rigid walls of a box, within a double bag of material, or lining a hole in the ground. Campers have created “instant hayboxes” by wrapping a sleeping bag, blankets, and/or pillows around a pot. The most effective insulating materials create many separate pockets of air, which slow down the movement of heat. Two to four inches of thickness, depending on the material, are necessary for good insulation. Some materials, such as aluminum foil or mylar, actually reflect heat back toward the pot.
Any material used must withstand temperatures up to 212 degrees F without melting (exposed styrofoam won’t work), and without releasing toxic fumes or dangerous fibers (rigid foam and fiberglass both need to be covered). The insulation also must be dry, and be kept dry (an inner layer of aluminum foil or mylar can help prevent cooking moisture from entering the wall of the box). The box should be as snug-fitting as possible around the pot, with a tight seal so that heat does not escape from the cooking cavity. Build your haybox to fit your largest pot; for smaller pots in the same box, you can increase performance by wrapping towels, blankets, or pillows around the pot.
Hayboxes used on a regular basis or in a group setting need to be durable: I’d recommend constructing a wooden box, with a “hat” type lid (so that the opening is at the bottom, to minimize heat loss). Attach handles to make lifting this upper section easier, and line the inner walls with mylar if possible (it can be salvaged from used food storage containers, balloons, etc.). If you can’t find mylar, be prepared to replace your aluminum foil lining periodically. Depending on where you are using the haybox, you may want to attach casters to the bottom of your base. Find a good place to store and use your haybox, within or easily accessible to the kitchen.
One final guarantee: once you’re a haybox devotee, you will never willingly go back to conventional methods of preparing pots of grains, beans, or long-cooking soups again, especially if you’re feeding a group. Happy cooking!
A different version of this article first appeared in the Summer 2002 issue of Communities: Journal of Cooperative Living (see www.ic.org).
For further information, contact Aprovecho Research Center, 80574 Hazelton Rd., Cottage Grove, OR 97424, (541) 942-8198, apro@efn.org, www.efn.org/~apro.
Chris Roth is a haybox devotee living at Lost Valley Educational Center.
©2003 Talking Leaves
Spring 2003
Volume 13, Number 1
Communication & Eco-Culture
Haybox
January 18, 2008 — thermalcookerhttp://www.lostvalley.org/haybox1.html
Hayboxes
Haybox cooking (also called retained-heat cooking) is an age-old method that can be used to conserve energy not only during times of crisis, but anytime. Depending on the food item and amount cooked, the use of a haybox or insulated cooker saves between 20% and 80% of the energy normally needed to cook a food. The longer an item usually takes on a stovetop, the more fuel is saved. For example, with a haybox, five pots of long-cooking dry beans will use the same amount of fuel to cook to completion as just one pot cooked without a haybox.
The principle of retained-heat cooking is simple. In conventional cooking, any heat applied to the pot after it reaches boiling temperature is merely replacing heat lost to the air by the pot. In haybox cooking, food is brought to a boil, simmered for a few minutes depending on the particle size (5 minutes for rice or other grains, 15 minutes for large dry beans or whole potatoes), then put into the haybox to continue cooking. Since the insulated cooker prevents most of the heat in the food from escaping into the environment, no additional energy is needed to complete the cooking process. The hayboxed food normally cooks within one to two times the normal stovetop cooking time. It can be left in the haybox until ready to serve, and stays hot for hours. “Timing” is much less important than in stovetop cooking: stick a pot of rice, beans, or stew in at lunch time, and it will be ready when you are, and steaming hot, at dinner time.
The haybox itself is any kind of insulated container that can withstand cooking temperatures and fits relatively snugly around the pot. Hayboxes have been made using hay, straw, wool, feathers, cotton, rice hulls, cardboard, aluminum foil, newspaper, fiberglass, fur, rigid foam, and/or other suitable materials as insulation. The insulation is placed between the rigid walls of a box, within a double bag of material, or lining a hole in the ground. “Instant hayboxes” have been created by wrapping a sleeping bag, blankets, and/or pillows around a pot. The most effective insulating materials create many separate pockets of air, which slow down the movement of heat. 2 to 4 inches of thickness (depending on the material) are necessary for good insulation. Some materials, such as aluminum foil or mylar, actually reflect heat back toward the pot. Important characteristics of any insulating material incorporated into a haybox include:
- It must withstand cooking temperatures (up to 212 degrees F or 100 degrees C) without melting.
- It does not release toxic fumes (any kind of foam insulation needs to be covered with aluminum foil or mylar) or dangerous fibers (fiberglass also needs to be covered).
- It can be fashioned to be as snug-fitting as possible around the pot. A little pot in a big box will not cook as effectively; it’s better to wrap pillows, towels, or blankets around it to fill up the space.
- It can be made to form a relatively tight seal, so that heat does not escape from the cooking cavity. Since hot air rises, a container designed to open at the base rather than the top will retain more heat.
- It is dry, and can be kept dry, since wet materials don’t insulate as well. An inner layer of aluminum foil or mylar helps keep cooking moisture from entering the walls of the box. Mylar, which can be salvaged from used food storage containers, balloons, etc., tends to be a more durable inner layer than aluminum foil.
Cooking containers, too, should have tight-fitting lids, to prevent the escape of heat and moisture.
Since water is not lost in haybox cooking the way it is during extended stovetop simmering, the amount of water used to cook grains and beans is normally reduced by one-quarter. Instead of adding 2 cups of water per cup of dry rice, try adding 1 1/2. Also, the larger the amount cooked, the more effective haybox cooking is, since a full pot has more mass and therefore more heat storage capacity than a half-full pot. Haybox cooking is ideally suited for a family or large group, or anytime there’s a reason to cook in quantity. If you’re cooking alone, try cooking full pots of food using a haybox, then reheating small portions for individual meals–this too can conserve fuel.Retained-heat cooking has many other advantages in addition to energy and water conservation. As mentioned, it makes “timing” less critical, since it keeps meals hot until serving time. Once the initial boil-and-short-simmer stage is past, it also eliminates the danger of burning the food on the bottom of the pot (the sad fate of too many pots of grains, beans, or other foods left simmering too long without stirring on the stove). Hayboxed food can actually be better for you, and tastier, than food prepared exclusively on a stovetop, because most of the cooking takes place in the 180 degrees F to 212 degrees F range, rather than at a constant 212 degrees F (lower temperatures preserve more flavor and nutrients, as they also do in crockpot cooking and solar cooking).
If you want to prepare multiple items for a meal but have only a limited number of flame sources, hayboxes can also greatly facilitate the logistics of food preparation. For example, you can bring your beans to a boil, simmer them 15 minutes, put them in a haybox; then bring your rice to a boil, simmer it 5 minutes, put it in another haybox; then prepare your vegetable stir-fry or soup, etc. At the end, you’ll have a uniformly hot, unburnt, multi-dish meal, all off a single flame, probably consuming less total fuel than you would have used simply to cook the longest-cooking item alone without a haybox. You’ll also have used one-quarter less of your drinkable water supply in preparing the food.
Presoaking and draining beans always makes them easier to cook, as well as to digest. A few particularly long-cooking foods, such as garbanzo beans, may need reboiling part-way through the cooking process. For health reasons, meat dishes should always be reboiled before serving.
Hayboxes are second only to solar cookers (which, however, are dependent on sunshine) in their potential to conserve resources. They’re easy to build, easy to use, and have many other advantages. Y2K or no Y2K, they deserve a place in every home.
Retained Heat Cooking
January 18, 2008 — thermalcookerhttp://solarcooking.org/heat-retention/ret-heat.htm
Once food is heated to boiling, cooking can continue in an insulated box
Daily cooking [on a stove or over a fire] frequently includes a long simmering period which is required for many beans, grains, stews, and soups. The amount of fuel needed to complete these cooking processes can be greatly reduced by cooking with retained heat. Even today, in some parts of the world, a pit is dug and lined with rocks previously heated in a fire. The food to be cooked is placed in the lined pit, often covered with leaves. Then the whole thing is covered with a mound of earth. The heat from the rocks cannot [easily] escape and the food is cooked very slowly.
Another version of this method consists of digging a pit and lining it with hay or another good insulating material. A pot of food which has previously been heated up to a boil is placed in the pit, covered with more hay and earth, and allowed to cook slowly with the retained heat.
This latter method is the direct ancestor of the “Haybox Cooker,” which is simply a well-insulated box or basket lined with a reflective material into which a pot of food previously brought to a boil is placed. The insulation greatly slows the loss of conductive heat, and the shiny lining reflects the radiant heat back into the pot. This works best when the pot fits snugly into the insulation with no air in between.
Such a box or basket can easily be made of inexpensive, locally available materials. It can be wooden, or cardboard, or any combination. Hay, straw, rushes, feathers, sawdust, rags, wool, shredded paper, etc. are all good insulating materials.
Principles to be kept in mind are these:
- Insulation should cover all six sides of the box.
- The box should be airtight.
- The inner surfaces of the box should be of a heat-reflective material.
There are some adjustments involved in cooking with haybox cookers:
- Less water should be used since it is not boiled away.
- Less spice in needed since the aroma is not boiled away.
- Cooking must be started earlier to give the food enough time to cook at a lower temperature than on the solar cooker or over a fire.
- The food should boil for several minutes before being placed in the box. This ensures that all the food is at boiling temperature, not just the water.
- Haybox cookers work best for large quantities, as small amounts of food have less thermal mass and cool Preheated stones could always be put in together with the pot to prove the additional thermal mass needed to keep the temperature up over a long period of time.
(This above portion of this article was excerpted from Cooking with the Sun, State Technical College, Altötting, Neuötting Str. 64 c, 84503, Altötting, Germany)
