{"items": [{"author": "Mac", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113514622622", "anchor": "fb-10100113514622622", "service": "fb", "text": "There are wide mouth thermi designed for solid foods. But the bigger lid is a worse heat leak. Another tack is to prepare the food such that most of the harmful bacteria are killed. I have had long simmered chili go most of a day without adequate cooling or heat retention.
Also, if you have the hardware, immersed thermal couples make for better data capture.", "timestamp": "1569851256"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113514622622&reply_comment_id=10100113515046772", "anchor": "fb-10100113514622622_10100113515046772", "service": "fb", "text": "→ Walker can you give an example of a thermos designed to keep dry foods safely hot? Everything I'm finding says insulation alone isn't enough for this because dry foods don't have enough heat capacity.", "timestamp": "1569851554"}, {"author": "Mac", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113514622622&reply_comment_id=10100113519572702", "anchor": "fb-10100113514622622_10100113519572702", "service": "fb", "text": "→ My experience is years old. Your current Google search is likely more accurate. I had not considered the issue of low specific heat in dry foods.
Perhaps have a section of brass or copper pipe, heated in the oven, and then inserted as a lining into the Thermos. There are houses that will tin plate it for you. \"Copper shot\" also exists. Of course, not suitable for food contact. But high spec heat metals rapidly become a weight issue.
You can also oversize the Thermos and insert an insulating disk under the lid. Does there exist a Thermos with a vacuum-insulated lid?
My best guess is an oversized container with added internal foam insulation. But that's apt to be a gallon container with a pint of food. Her friends will laugh.
Nesting vacuum bottles, or flasks?
Increase insulation or increase heat packed into the container. Right, duh. MREs with flameless ration heaters? Mebbe not. :)", "timestamp": "1569853673"}, {"author": "Peter", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113519727392", "anchor": "fb-10100113519727392", "service": "fb", "text": "Joulies are a product which contain a substance which undergoes a phase change. Unfortunately the target temperature is too low for your purpose and they take up a lot of volume.", "timestamp": "1569853785"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113519727392&reply_comment_id=10100113520795252", "anchor": "fb-10100113519727392_10100113520795252", "service": "fb", "text": "→ I'm not too worried about volume, but yes if we wanted to use a phase-change material we'd need one above 140F. https://en.wikipedia.org/wiki/Phase-change_material lists many options.", "timestamp": "1569854456"}, {"author": "Danner", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113523814202", "anchor": "fb-10100113523814202", "service": "fb", "text": "It seems like ceramics would be a good material to add extra heat to a thermos. Heat a pottery brick to 300F in the oven, then drop it in with the rice? The idea would be to let out the heat slow enough to not burn the rice, and not injure the thermos too bad.
Glass would be another idea, it holds more heat than ceramics. Marbles? I'd be worried about shattered glass.
Apparently they make soapstone for this purpose, http://www.ctsoapstone.com/soapstone-trays.htm", "timestamp": "1569855726"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113523814202&reply_comment_id=10100113524088652", "anchor": "fb-10100113523814202_10100113524088652", "service": "fb", "text": "→ Danner good ideas! Marbles would be dangerous to include in a kid's lunch, though!", "timestamp": "1569856049"}, {"author": "Jillian", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113523814202&reply_comment_id=10100113947679772", "anchor": "fb-10100113523814202_10100113947679772", "service": "fb", "text": "→ A small glass bowl maybe?", "timestamp": "1570056602"}, {"author": "Danner", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113524253322", "anchor": "fb-10100113524253322", "service": "fb", "text": "I also like the idea of a ziplock bag of rice, surrounded by boiling water in the thermos. It would be easy to pull out the rice, and hell, you could use another liquid food instead of water as the thermal mass. These indian meals are amazing, and you could heat them in the morning, put the bag of rice in, and then combine them at school.
https://www.amazon.com/dp/B002JF62GU/", "timestamp": "1569856125"}, {"author": "Ruthan", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113524253322&reply_comment_id=10100113524597632", "anchor": "fb-10100113524253322_10100113524597632", "service": "fb", "text": "→ If there is anyone is willing to bother figuring out exactly how hot curry needs to be in order for it to be warm enough to eat but not so hot it will burn your fingers, I believe it is Jeff. However, it sounds like a bit of a mess, especially for a five year old.", "timestamp": "1569856513"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113524253322&reply_comment_id=10100113524912002", "anchor": "fb-10100113524253322_10100113524912002", "service": "fb", "text": "→ Yeah, this would not work for many kindergarteners", "timestamp": "1569856626"}, {"author": "Danner", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113524253322&reply_comment_id=10100113525401022", "anchor": "fb-10100113524253322_10100113525401022", "service": "fb", "text": "→ Yep, totally right. But I put it out there, since this is Jeff we're talking about.
I think I'd rather seek a totally different avenue than this, but like Jeff, I enjoy thinking of all the possible options before honing in on something that would actually work. Brainstorming!", "timestamp": "1569856816"}, {"author": "Kitty", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113524253322&reply_comment_id=10100113575859902", "anchor": "fb-10100113524253322_10100113575859902", "service": "fb", "text": "→ I would also be wary of plastic leeching in the case of a bag in boiling water.", "timestamp": "1569878273"}, {"author": "Hollis", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113524253322&reply_comment_id=10100114038707352", "anchor": "fb-10100113524253322_10100114038707352", "service": "fb", "text": "→ Kitty they're usually advertised for that purpose, and my friend the food process engineer told me a while back that the plastics they use for those things don't leach anything until they reach way hotter temperatures than 100C.", "timestamp": "1570077075"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113524253322&reply_comment_id=10100114052509692", "anchor": "fb-10100113524253322_10100114052509692", "service": "fb", "text": "→ Hollis on the other hand I think maybe we've had several rounds now of \"this plastic is effectively inert and safe for food\" and then years later moving away from it?", "timestamp": "1570098085"}, {"author": "Hollis", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113524253322&reply_comment_id=10100114077973662", "anchor": "fb-10100113524253322_10100114077973662", "service": "fb", "text": "→ True fact, and I asked that question and got an answer that seemed well-considered and rooted in skeptical inquiry rather than press-release puffery. That being said, of course, we can't know everything, but my friend was unconcerned about the plastics his company had access to. Not sure what that means for the broader context.", "timestamp": "1570112695"}, {"author": "Frederic", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113524253322&reply_comment_id=10100114155603092", "anchor": "fb-10100113524253322_10100114155603092", "service": "fb", "text": "→ A lot of places recommend using ziplock bags for sous vide cooking. This seems analogous.", "timestamp": "1570147588"}, {"author": "Ruthan", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113525241342", "anchor": "fb-10100113525241342", "service": "fb", "text": "I get decent mileage (probably not good enough for this purpose, but it does help) from putting thermal mugs inside an old sock, twisted at the top and then doubled over. But maybe one could wrap the thermos in a hot pack of some kind?", "timestamp": "1569856683"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113525515792", "anchor": "fb-10100113525515792", "service": "fb", "text": "There are substitute ice cubes that should work for heat as well:", "timestamp": "1569856892"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113525515792&reply_comment_id=10100113525525772", "anchor": "fb-10100113525515792_10100113525525772", "service": "fb", "text": "→ https://www.amazon.com/.../B07N.../ref=asc_df_B07NZV5LP1/...", "timestamp": "1569856898"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113525515792&reply_comment_id=10100113525815192", "anchor": "fb-10100113525515792_10100113525815192", "service": "fb", "text": "→ https://www.amazon.com/.../B008.../ref=asc_df_B0085VOERQ/...", "timestamp": "1569857060"}, {"author": "Evan", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113525515792&reply_comment_id=10100113533215362", "anchor": "fb-10100113525515792_10100113533215362", "service": "fb", "text": "→ Yeah, they ought to have more heat capacity than a stone.", "timestamp": "1569860645"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113525515792&reply_comment_id=10100113537102572", "anchor": "fb-10100113525515792_10100113537102572", "service": "fb", "text": "→ Evan aren't they stones?", "timestamp": "1569862239"}, {"author": "Evan", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113525515792&reply_comment_id=10100113538604562", "anchor": "fb-10100113525515792_10100113538604562", "service": "fb", "text": "→ Oh, I didn't actually look at the links, I thought these were the phase-change \"stones\". Like these:
https://smile.amazon.com/Kollea-Stainless.../dp/B00EWAWZAC/
These have a glycol/water solution in them (or something like that; I assume details vary a little), basically the same as ice chest freezer pack things, but in a metal case. The important part for this purpose is that they're mostly water in a sealed container, which is better than actual stone.", "timestamp": "1569862983"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113525515792&reply_comment_id=10100113542277202", "anchor": "fb-10100113525515792_10100113542277202", "service": "fb", "text": "→ Evan phase change is good, but then you need something designed for hot food temperatures", "timestamp": "1569864702"}, {"author": "Evan", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113525515792&reply_comment_id=10100113543634482", "anchor": "fb-10100113525515792_10100113543634482", "service": "fb", "text": "→ You're not making use of the phase change here, merely the higher heat capacity of water vs your rocks.", "timestamp": "1569865308"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113525515792&reply_comment_id=10100113572651332", "anchor": "fb-10100113525515792_10100113572651332", "service": "fb", "text": "→ Evan I don't know about this brand, but another one I looked at had terrible reviews for leaking.", "timestamp": "1569877110"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113525515792&reply_comment_id=10100114131177042", "anchor": "fb-10100113525515792_10100114131177042", "service": "fb", "text": "→ I was suggesting the stone I've cubes as a way of getting \"rocks\" in a convenient and easy to clean form, and under the delusion that soapstone would be better than, say, steel. This was before I looked up the specific heat chart.", "timestamp": "1570138844"}, {"author": "David Chudzicki", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113532072652", "anchor": "fb-10100113532072652", "service": "fb", "text": "I sometimes use whiskey stones for cooling drinks. Could be used for the reverse? I dunno, maybe needlessly expensive, etc. But easier to clean than a rock.", "timestamp": "1569860248"}, {"author": "Danner", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113532072652&reply_comment_id=10100113535795192", "anchor": "fb-10100113532072652_10100113535795192", "service": "fb", "text": "→ Are whiskey stones soapstone? I linked a thing where they were used to keep food warm as a tray to put under your dish.", "timestamp": "1569861639"}, {"author": "Bill", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113536229322", "anchor": "fb-10100113536229322", "service": "fb", "text": "The problem is not with the insulation of the thermos, but with the specific heat of the food. Water, and food that is mostly water, has a specific heat of 1 Btu per lb-F. This is the highest of common substances, and certainly the highest of edible substances. This is why a hot rock doesn't help much (http://zeus.phys.uconn.edu/.../heating-10-2004/heatcap.html).
Dry food just can't hold as much heat, so in the same thermos, at the same ambient conditions, it will cool more quickly.
A phase-change material is a good general solution to the problem, as the latent heat of melting/solidification is usually much higher than the specific heat of the substance without phase change. But the substance has to be selected so that it changes phase at about the desired temperature, say 150 to 200 F. Some of the salts used in thermal energy storage for solar power would be good choices, if they were affordable and non-toxic.
More insulation is also a good general; wrap the thermos in a fiberglass blanket and put it in a styrofoam cooler. But this may not be practical for a child's lunch box.
The best solution for this problem is food that does not require refrigeration to stay wholesome for several hours - like peanut butter, cheese, or cured meat (with no mayonnaise).", "timestamp": "1569861840"}, {"author": "Danner", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113536229322&reply_comment_id=10100113538305162", "anchor": "fb-10100113536229322_10100113538305162", "service": "fb", "text": "→ I'm pretty sure thermal salts are for liquid salts, at like 500-1000F. Also, the specific heat doesn't look at some other practical issues, like total heat capacity and density and conductivity. Cork has a high specific heat capacity, but not enough density for it to be useful in storage.
Here's a better link, and you can sort by Volumetric heat capacity and see that yes, water is on top, followed by some useful solids that don't phase change to steam, steel and iron. Glass and Granite are about half as good as water, but still on the table if you're ok with double the volume or double the temperature.
https://en.wikipedia.org/.../Table_of_specific_heat...", "timestamp": "1569862875"}, {"author": "Bill", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113536229322&reply_comment_id=10100113538923922", "anchor": "fb-10100113536229322_10100113538923922", "service": "fb", "text": "→ Of course. (And this is actually my professional field, so I can easily go into too much detail)", "timestamp": "1569863162"}, {"author": "Danner", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113536229322&reply_comment_id=10100113539078612", "anchor": "fb-10100113536229322_10100113539078612", "service": "fb", "text": "→ Bill Cool! Like, materials science, or cooking and insulating, or...", "timestamp": "1569863237"}, {"author": "Bill", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113536229322&reply_comment_id=10100113539213342", "anchor": "fb-10100113536229322_10100113539213342", "service": "fb", "text": "→ BTW, thanks for bringing the extra lights to BIDA last night. I have a few ideas to turn over for the next techno, I'll friend you if I haven't already.", "timestamp": "1569863285"}, {"author": "Bill", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113536229322&reply_comment_id=10100113539647472", "anchor": "fb-10100113536229322_10100113539647472", "service": "fb", "text": "→ mechanical engineering, with a concentration on thermal engineering, heat transfer and fluid mechanics. The cooking of a turnip was a sample problem in a grad school class, as an example of transient heat transfer.", "timestamp": "1569863485"}, {"author": "Danner", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113536229322&reply_comment_id=10100113540166432", "anchor": "fb-10100113536229322_10100113540166432", "service": "fb", "text": "→ I do worry about the conductivity of a chunk of stainless steel at 300F burning the rice instead of keeping it warm. We're looking for a good volumetric heat density object, with low thermal conductivity. Maybe steel with a insulator around it?", "timestamp": "1569863707"}, {"author": "Bill", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113536229322&reply_comment_id=10100113542152452", "anchor": "fb-10100113536229322_10100113542152452", "service": "fb", "text": "→ Yes, the problem here is the low conductivity of the dry rice. the heat stored in the steel can transfer swiftly to the surface, keeping it hot, but the heat transfer into the rice would be slow. Consequence, rice at the near surface would dry out and be crunchy, but rice at the far surface would be much cooler, perhaps cool enough to cause a problem.", "timestamp": "1569864580"}, {"author": "Mac", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113536229322&reply_comment_id=10100114139051262", "anchor": "fb-10100113536229322_10100114139051262", "service": "fb", "text": "→ Objection! I think mass specific heat is most important for consideration of the amount of weight (right -- not equal to mass) one has to lug around.", "timestamp": "1570141365"}, {"author": "Carl", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113541393972", "anchor": "fb-10100113541393972", "service": "fb", "text": "...
Maybe a chunk of stainless steel, heated with the pre-heat water.", "timestamp": "1569864190"}, {"author": "Danner", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113541393972&reply_comment_id=10100113541773212", "anchor": "fb-10100113541393972_10100113541773212", "service": "fb", "text": "→ I think this is worth an experiment. The steel will be about 50% better than stone of the same size. 212F is low enough to keep the steel from burning the rice. And the steel can be made into an easily cleanable shape that fits in the thermos.
Volumetric Heat Capacity
Water: 4.2 cm^3*K
Steel: 3.7 cm^3*K
Granite: 2.2 cm^3*K
It's a good improvement, much closer to water.", "timestamp": "1569864316"}, {"author": "Bill", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113541393972&reply_comment_id=10100113541987782", "anchor": "fb-10100113541393972_10100113541987782", "service": "fb", "text": "→ Even better, divide the steel into two cylindrical tablets, OD as the ID of the the thermos. Place one in the bottom, place the rice, place the other on the top. This would keep the rice more evenly warm.", "timestamp": "1569864495"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113541393972&reply_comment_id=10100113542212332", "anchor": "fb-10100113541393972_10100113542212332", "service": "fb", "text": "→ Bill one on top of the food would get in the way of eating it", "timestamp": "1569864642"}, {"author": "Bill", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113541393972&reply_comment_id=10100113542791172", "anchor": "fb-10100113541393972_10100113542791172", "service": "fb", "text": "→ Jeff Kaufman Of course! Take the top cylinder out first; perhaps with a bit of string on the backside so it can be grabbed with the bare fingers.", "timestamp": "1569864942"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113541393972&reply_comment_id=10100113542905942", "anchor": "fb-10100113541393972_10100113542905942", "service": "fb", "text": "→ Bill I'm not sure that's something a kindergartener will reliably do unassisted", "timestamp": "1569865056"}, {"author": "Carl", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113541393972&reply_comment_id=10100113543045662", "anchor": "fb-10100113541393972_10100113543045662", "service": "fb", "text": "→ Jeff Kaufman , lunch comes with pliers?", "timestamp": "1569865125"}, {"author": "Bill", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113541393972&reply_comment_id=10100113543120512", "anchor": "fb-10100113541393972_10100113543120512", "service": "fb", "text": "→ Jeff Kaufman She'll only make the mistake once - and she'll have hot, wholesome, tasty food all year.", "timestamp": "1569865160"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113541393972&reply_comment_id=10100113573354922", "anchor": "fb-10100113541393972_10100113573354922", "service": "fb", "text": "→ Danner A few 1\" ball bearings seem like a good place to start. No machining needed.", "timestamp": "1569877364"}, {"author": "Danner", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113541393972&reply_comment_id=10100113577032552", "anchor": "fb-10100113541393972_10100113577032552", "service": "fb", "text": "→ Guess those would be hard to swallow... Spherical is good.. checks out! Biggest ball bearing that fits in the thermos.", "timestamp": "1569878700"}, {"author": "Bill", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113542491772", "anchor": "fb-10100113542491772", "service": "fb", "text": "Another good solution is the \"tiffin-wallah\". Cook the food at home, at lunch time, and hire a low-wage gig worker to deliver it swiftly to the child at school. (A mixed blessing!)
https://en.wikipedia.org/wiki/Dabbawala", "timestamp": "1569864782"}, {"author": "Carl", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113542706342", "anchor": "fb-10100113542706342", "service": "fb", "text": "Oily food?
Young brains need fat...
http://www2.ucdsb.on.ca/.../Specific_Heat_Capacity_Table...", "timestamp": "1569864885"}, {"author": "Bill", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113542706342&reply_comment_id=10100113543055642", "anchor": "fb-10100113542706342_10100113543055642", "service": "fb", "text": "→ The problem as stated is for dry rice. But myself, I think something like jambalaya, curry-raisu, or biryani would be a better meal that would also have enough moisture to stay hot.", "timestamp": "1569865128"}, {"author": "Julia", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113542706342&reply_comment_id=10100113591548462", "anchor": "fb-10100113542706342_10100113591548462", "service": "fb", "text": "→ This is rice with quite a bit of butter mixed in, but still most of the space is taken with rice and air.", "timestamp": "1569885004"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113542706342&reply_comment_id=10100113598215102", "anchor": "fb-10100113542706342_10100113598215102", "service": "fb", "text": "→ I tested with plain rice because it was easier and more conservative, but yes when I do it for real there's quite a lot of butter", "timestamp": "1569888086"}, {"author": "Alex", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113546663412", "anchor": "fb-10100113546663412", "service": "fb", "text": "I'm thinking about a https://en.wikipedia.org/.../Radioisotope_thermoelectric...... Plutonium would keep it nice and hot for a long time, but might be tricky to work with for a kindergartner", "timestamp": "1569866994"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113546962812", "anchor": "fb-10100113546962812", "service": "fb", "text": "This table suggests that something like a small stainless steel or tin container filed with water will give you the most heat capacity, both by volume AND by added weight. Steel would be the next best by volume, but would add more weight.
https://en.m.wikipedia.org/.../Table_of_specific_heat...", "timestamp": "1569867176"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113546962812&reply_comment_id=10100113547097542", "anchor": "fb-10100113546962812_10100113547097542", "service": "fb", "text": "→ Soapstone wasn't on that table, but here it is. It's not as good as water or steel, but not a terrible choice by volume.
\"The specific heat capacity of soapstone is about 1 J/gK and its density about 3 g/cm\u00b3, making its volumetric heat capacity 3 J/cm\u00b3K. The mineral magnesite has good thermal conductivity and heat capacity. The specific heat capacity for natural stone is usually 0.84 J/gK, making the value for soapstone about 20% greater than average.\"", "timestamp": "1569867265"}, {"author": "Danner", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113546962812&reply_comment_id=10100113553240232", "anchor": "fb-10100113546962812_10100113553240232", "service": "fb", "text": "→ Michael cool, I was looking for those details. Added to my list:
Volumetric Heat Capacity
Water: 4.2 J/cm\u00b3K
Steel: 3.7 J/cm\u00b3K
Soapstone: 3 J/cm\u00b3K
Granite: 2.2 J/cm\u00b3K", "timestamp": "1569869590"}, {"author": "Bob", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113569263122", "anchor": "fb-10100113569263122", "service": "fb", "text": "lydia: Jeff's post raises concerns for the takeway box strategy (at least for me, with multiple hours after some meals).", "timestamp": "1569875872"}, {"author": "opted out", "source_link": "#", "anchor": "unknown", "service": "unknown", "text": "this user has requested that their comments not be shown here", "timestamp": "1569878103"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113575330962&reply_comment_id=10100113598389752", "anchor": "fb-10100113575330962_10100113598389752", "service": "fb", "text": "→ Justin there's a link to one in the post! But it's targeting 136F which is too cool", "timestamp": "1569888160"}, {"author": "Kiran", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113590939682", "anchor": "fb-10100113590939682", "service": "fb", "text": "I'm guessing that a travel Crock-Pot or Hot Logic cooker won't work because she wouldn't be allowed to plug them into wall power.", "timestamp": "1569884617"}, {"author": "opted out", "source_link": "#", "anchor": "unknown", "service": "unknown", "text": "this user has requested that their comments not be shown here", "timestamp": "1569889685"}, {"author": "Mac", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113663833602", "anchor": "fb-10100113663833602", "service": "fb", "text": "Maybe volumetric heat capacity is not what needs to be optimized, but rather mass heat capacity, ie, Joules per gram that ya gotta lug around. While paraffin and polyeth are surprisingly high heat capacity, aluminum is probably the best non-phase change solution. Get a section of aluminum tube from McMaster-Carr. Put it in a wide mouth vacuum container. Get it food-safe hard coat/anodized like a fry pan. Let it contact the food. Wash it after. Avoid using plastic bags for separation.", "timestamp": "1569901559"}, {"author": "Michael", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113663833602&reply_comment_id=10100113669113022", "anchor": "fb-10100113663833602_10100113669113022", "service": "fb", "text": "→ Mac I also expected aluminum to be the answer, but water seems to be best for both volume and weight, and steel if you don't care about weight and don't want to use water.", "timestamp": "1569903811"}, {"author": "Mac", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113663833602&reply_comment_id=10100113705854392", "anchor": "fb-10100113663833602_10100113705854392", "service": "fb", "text": "→ Learned something. Thanks", "timestamp": "1569939411"}, {"author": "Aaron", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113667097062", "anchor": "fb-10100113667097062", "service": "fb", "text": "A slightly related problem: recently, I've been spending a lot of time at the library. I like to bring beans and rice for my lunch. The problem is, the library doesn't have a microwave. The thing I settled on is this object: https://amzn.to/2oHqAnw
The rough idea is that you plug it in for about 1.5-2 hours before you'd like to eat the food and it will have brought the food up to a comfortable, safe eating temperature.", "timestamp": "1569902499"}, {"author": "Aaron", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113667097062&reply_comment_id=10100113667481292", "anchor": "fb-10100113667097062_10100113667481292", "service": "fb", "text": "→ By comfortable temperature I mean, the cheese I put at the top of the container has thoroughly melted, steam is released as I open the container and there are no cold spots. I use the 12oz glasslock containers.", "timestamp": "1569902677"}, {"author": "Jeff Kaufman", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113667097062&reply_comment_id=10100113687640892", "anchor": "fb-10100113667097062_10100113687640892", "service": "fb", "text": "→ That makes sense for your situation, but isn't something that would work in an elementary school", "timestamp": "1569926859"}, {"author": "Kiran", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113667097062&reply_comment_id=10100113704452202", "anchor": "fb-10100113667097062_10100113704452202", "service": "fb", "text": "→ That's the device I mentioned above. Crock-Pot also makes one.", "timestamp": "1569938670"}, {"author": "Aloysius", "source_link": "https://www.facebook.com/jefftk/posts/10100113510311262?comment_id=10100113692181792", "anchor": "fb-10100113692181792", "service": "fb", "text": "Also depends on where the thermos will be sitting what\u2019s the temperature of the room could it be placed in direct sunlight if I put stuff in my stainless thermos stuff that I want to keep cold if I put it in the refrigerator It will extendthe cold time", "timestamp": "1569930231"}, {"author": "Kenny", "source_link": "https://www.lesswrong.com/posts/JCEpS5WGkgNiCXdbR#iQeo2gBDoGizK2pQC", "anchor": "lw-iQeo2gBDoGizK2pQC", "service": "lw", "text": "I was disappointed that Jeff didn't conclude, based on the detailed evidence he found, that it's probably fine to just pack the rice in a regular un-modified thermos.\n
Or am I way off in summarizing his evidence this way?\n", "timestamp": 1571419186}, {"author": "jkaufman", "source_link": "https://www.lesswrong.com/posts/JCEpS5WGkgNiCXdbR#367vcgxGG3pCPKwYC", "anchor": "lw-367vcgxGG3pCPKwYC", "service": "lw", "text": "→ See the follow-up where I conclude that this is overkill for 4hr: https://www.lesswrong.com/posts/44jR8GD6ofKWvxq9D/what-is-the-real-danger-zone-for-food\n", "timestamp": 1571431437}, {"author": "Kenny", "source_link": "https://www.lesswrong.com/posts/JCEpS5WGkgNiCXdbR#QvAzfd6qJb8JL7xr5", "anchor": "lw-QvAzfd6qJb8JL7xr5", "service": "lw", "text": "→ → My bad \u2013 I read that follow-up and was disappointed in the last sentence:\n\n
To be safe, though, I'm going to keep using the thermal mass thermos approach.\n\n
It doesn't seem like the thermal mass thermos is strictly necessary \"to be safe\", but I understand your extra abundance of caution.\n", "timestamp": 1571677287}]}