# Pizza delivery thermodynamics **URL:** \ **Category:** Factual Questions\ **Created:** [November 19, 2022, 11:39pm UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224 "2022-11-19T23:39:49Z")\ **Posts on this page:** 17\ **Page:** 4
**Author:** ![StarvingButStrong](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/starvingbutstrong/32/335_2.png) [@StarvingButStrong](https://boards.straightdope.com/u/StarvingButStrong)\ **Post date:** [November 23, 2022, 3:39pm UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/61 "2022-11-23T15:39:34Z")
> [@ZurBob](#): > > It is a run of the mill cardboard pizza box. Nobody seems to have looked at that aspect yet. There doesn’t seem to _be_ run of the mill cardboard pizza boxes. Of the two closest places to my house, the cheaper one uses a single-ply type cardboard, which is flimsier but generally works okay if you’re not too awkward in carrying it. The place that’s a little more expensive has corrugated cardboard cartons, which are stiffer and safer in handling, though a nuisance in our recycling bin. And there’s a third place also reasonably close that has boxes with triangular-walled-off corners, which maybe means less air in the box for the pizza to give up its heat too? But we don’t like their pizza for other reasons. Personally, ever since one disaster when a pizza oozed enough oil through its box to leave marks on the seat, we grab a couple of newspapers out of the recycling bin on our way out for a pizza run. One wad of paper on the seat, then the pizza, then the rest of the paper sections on top of the box. Don’t know if the extra insulation actually helps measurably, but it definitely protects the seats from the oils. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [November 23, 2022, 11:16pm UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/62 "2022-11-23T23:16:28Z")
> [@md-2000](#): > > **I think we want to stick to basic principles and first order effects.** Otherwise, too many variables Amen to that. (bolding mine) Think about it…we’ve barely entered the rabbit hole of variables. Surely, a consensus can be reached by adhering to the quote above? ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [November 24, 2022, 1:21am UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/63 "2022-11-24T01:21:55Z")
> [@k9bfriender](#): > > I should point out that the pizza doesn’t come out of the oven at 350, if it did, it would be a dried up husk. It’s usually more like 180 or so… Beg to differ. Went to a pizzeria today to pick up a few slices and inquired as to their oven temp. They said It was 500. Amazingly, I happened to have my Fluke IR in my pocket, and checked some temps. The oven was in fact 500 deg. (on average), and the pies (thin) coming out had a surface temp of appx. the same, while the thick crusts had appx. 410 deg surface temps. The few minutes it took to box them (just before closing the lid) resulted in an appx 40/50 degree drop. Do the math. The slices I purchased from under the counter heat lamp were considerably cooler, around 140 deg., bummer. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [November 24, 2022, 1:39am UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/64 "2022-11-24T01:39:15Z")
> [@StarvingButStrong](#): > > There doesn’t seem to _be_ run of the mill cardboard pizza boxes. The vast majority of pizza boxes are corrugated cardboard with a double panel led front wall - “Walker style”. Yeah there are a few that use non-corrugated cardboard, one very good pizza place near us just pack it up in a paper bag, but they are the not standard. The reason that that design is so pervasive is relevant to this exercise: you want heat retained but do not want the steam from the hot moist pie all trapped next to the pizza making the crust soggy in transit. The design allows steam to escape, traveling through the corrugated channels, condensing some on the relatively cooler outer cardboard and also some coming out of the box. Again, this raises the cooling impact of the moving layer of air above the box with fairly still cooler air under it, sucking the cooler air through the box and cooling the top of the box by way of phase change (evaporative cooling) of the moisture that gets wicked through that top cardboard layer. Even if that moving layer above is warm. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [November 24, 2022, 1:50am UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/65 "2022-11-24T01:50:26Z")
As an aside: I remember a pizzeria defunct from 30 years ago that was run by an old guy from Italy who made ONE style of pie, **SUPER THIN** … always put it in a giant thin paper bag… Never failed to be perfect when I got it home. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [November 24, 2022, 1:55am UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/66 "2022-11-24T01:55:28Z")
> [@DSeid](#): > > The reason that that design is so pervasive is relevant to this exercise: you want heat retained but do not want the steam from the hot moist pie all trapped next to the pizza making the crust soggy in transit. The design allows steam to escape, traveling through the corrugated channels, condensing some on the relatively cooler outer cardboard and also some coming out of the box. You are one who is quite the expert on pizza boxing! (meant as a compliment) ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [November 24, 2022, 3:05am UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/67 "2022-11-24T03:05:17Z")
Ya know folks, initially I was searching for a simplistic opinion and formula for the OP. I now realize that is un-obtanium here. However, there must be some middle ground concepts that lead to an educated opinion as to the OP that are not bogged down by the minutiae of (relatively) inconsequential variables, nor upon empirically derived notions. I’m looking for a rule of thumb. ---
**Author:** ![ASL\_v2.0](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/asl_v2.0/32/3525_2.png) [@ASL\_v2.0](https://boards.straightdope.com/u/ASL_v2.0)\ **Post date:** [November 24, 2022, 3:21am UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/68 "2022-11-24T03:21:11Z")
> [@ZurBob](#): > > I now realize that is un-obtanium here. Not just here. Anywhere. Take the pizza out of the box and maybe then it becomes amenable to a simplistic solution (maybe). But the box is a major complicating factor. It’s not just minutiae: it’s a whole set of confounding variables that have the potential to weigh heavily on one side of the problem or the other. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [November 24, 2022, 3:25am UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/69 "2022-11-24T03:25:35Z")
Allright, take the pizza out of the box if you prefer, what’s your notion? After all, we’re keeping all the variables the same. I feel the box is just an interim factor to the ultimate outcome ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [November 24, 2022, 11:37am UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/70 "2022-11-24T11:37:51Z")
> [@ZurBob](#): > > I feel the box is just an interim factor to the ultimate outcome Yes, but for the time involved, the box may be really key. AGain pretending we’re really talking about pizza. e.g. & total WAG: box or not-box makes a huge difference on a 15-minute drive and none on a 45-minute drive. This is really the anwnwer you seek: > [@k9bfriender](#): > > That said, two things. First, I know that it’s not _really_ about pizza, but I should point out that the pizza doesn’t come out of the oven at 350, if it did, it would be a dried up husk. It’s usually more like 180 or so. So, we are dealing with a significantly less temperature difference than originally assumed by the problem. > … > That said, we can simplify things a little bit. For instance, if the heat coming out of the air vent is 180F or higher, then it will keep the pizza warm indefinitely. If the air coming out is 50F, then it will cool rapidly, with more airflow making it cool faster. > > So, there _is_ a point where the vent temperature will be high enough to keep the pizza warmer with it blowing on it than if it were in still air. _Where_ that point is is going to be nearly impossible to calculate, and will change based on a number of factors. I would say that a 115F heater is not going to cut it, it’s going to cause more heat loss than it contributes, but that’s a WAG. The moving air needs to be a LOT hotter than the ambient air for the extra warming heat transfer from the higher temperature to make up for the extra cooling heat transfer from moving air. A pizza, or a pizza box, is nearly all surface area with very little interior volume. That makes it very sensitive to all the forms of heat transfer, and it will rapidly gain or lose heat to reach balance with the net heat / cool flux impinging on it. ---
**Author:** ![DSeid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dseid/32/20194_2.png) [@DSeid](https://boards.straightdope.com/u/DSeid)\ **Post date:** [November 24, 2022, 5:45pm UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/71 "2022-11-24T17:45:36Z")
So how about we just look at a single component with an unboxed steamy hot pizza: evaporative cooling. Dry air rapidly blowing out of the vent across the surface of the pizza, even dry air warmer than the surface of the pizza, will speed up heat transfer by way of evaporative cooling compared to hypothetically still air. The difference between those two conditions should be a tractable problem … ---
**Author:** ![mmmiiikkkeee](https://avatars.discourse-cdn.com/v4/letter/m/edb3f5/32.png) [@mmmiiikkkeee](https://boards.straightdope.com/u/mmmiiikkkeee)\ **Post date:** [November 24, 2022, 6:39pm UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/72 "2022-11-24T18:39:34Z")
> [@ZurBob](#): > > Beg to differ. … … the pies (thin) coming out had a surface temp of appx. the same, while the thick crusts had appx. 410 deg surface temps. The few minutes it took to box them (just before closing the lid) resulted in an appx 40/50 degree drop. Do the math. I’m not following what your math is supposed to prove; you measured some surface temperatures and saw that they drop quickly… so what? An IR reader doesn’t tell you internal temperature, which is different from surface temperature. You can’t have liquid water inside a pizza at 500 degrees - it can’t exist in a liquid state at that temperature in an oven. Think about the difference between a potato chip and a french fry; the former is what happens when the internal temp hits really high ranges and the moisture is driven out. A pizza is like the latter with a temperature gradient between surface and internal temp. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [November 25, 2022, 2:44pm UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/73 "2022-11-25T14:44:59Z")
> [@ZurBob](#): > > Beg to differ. Went to a pizzeria today to pick up a few slices and inquired as to their oven temp. They said It was 500. Amazingly, I happened to have my Fluke IR in my pocket, and checked some temps. The oven was in fact 500 deg. I never said differently, however, oven temp is not the same as the temp of something _in_ the oven. > [@ZurBob](#): > > and the pies (thin) coming out had a surface temp of appx. the same, while the thick crusts had appx. 410 deg surface temps. The surface is where heat enters, and it is also where heat leaves, it is not the same as the internal temperature. > [@ZurBob](#): > > The few minutes it took to box them (just before closing the lid) resulted in an appx 40/50 degree drop. Right, because it’s only a very thin layer of the surface that is at that temperature, it doesn’t take long for that to cool down. > [@ZurBob](#): > > Do the math. Water boils at 212F. If the pizza is at 410F, how much water is left in it? You ever leave a pizza in the oven for too long? The reason that it burns is because instead of 180F or so, it is getting up to the temperatures where the water is driven off. This is what a pizza that has equalized temperature with the oven looks like. [![](https://external-preview.redd.it/gm1iGh8B0gNkMyc56_augHQObNTywcnXI7xq4DaSdDQ.jpg?auto=webp&s=b93a2f92efdf60433612734e82c8412d12c65545) ](https://external-preview.redd.it/gm1iGh8B0gNkMyc56_augHQObNTywcnXI7xq4DaSdDQ.jpg?auto=webp&s=b93a2f92efdf60433612734e82c8412d12c65545) > [@ZurBob](#): > > The slices I purchased from under the counter heat lamp were considerably cooler, around 140 deg., bummer. That’s the proper holding temperature for hot foods. If they held it at 180F, the slices would dry out and be inedible in a very short period. (If they held it at a lower temp, they would be risking food borne illness.) ---
**Author:** ![TokyoBayer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tokyobayer/32/13989_2.png) [@TokyoBayer](https://boards.straightdope.com/u/TokyoBayer)\ **Post date:** [November 26, 2022, 12:50pm UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/74 "2022-11-26T12:50:36Z")
> [@LSLGuy](#): > > Yes, but for the time involved, the box may be really key. AGain pretending we’re really talking about pizza. e.g. & total WAG: box or not-box makes a huge difference on a 15-minute drive and none on a 45-minute drive. I’m not sure about the 45 minutes, but it’s certainly true over a longer period of time. The test I linked to above shows that in a normal room temperature that a pizza in a box was cooling from 51.5 C to 38.8 F in 27 minutes while a pizza in a box with an additional foil liner took 37 minues to cool to about the same tempurature. At 15 minutes, there was two degrees C of difference, which is significent, IMHO. As the OP specifies that the car is 85 F or 29.4 C, then this is the lower limit. Eyeballing the graphs I’m not sure if it that tempurature would be reached in 45 minutes, but your greater point is correct. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [December 29, 2022, 3:54am UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/75 "2022-12-29T03:54:12Z")
> [@mmmiiikkkeee](#): > > I’m not following what your math is supposed to prove; you measured some surface temperatures and saw that they drop quickly… so what? An IR reader doesn’t tell you internal temperature, which is different from surface temperature. You can’t have liquid water inside a pizza at 500 degrees - it can’t exist in a liquid state at that temperature in an oven We’re talking about a pizza consisting of appx. 1/16" crust and 1/16" toppings (total 1/8" thick). After appx 10 minutes in 500 degree convection… and considering that the heat input to the pie is coming from the bottom **and** the top, it is not unreasonable to _assume_ (more on this assumption later) that a surface temp reading would roughly equate to the internal temperature. So yes, based on circumstances, an external IR reading can reflect the internal temperature of an object. I’ve spent way too much time and effort in the last month trying to sort this out, but here’s what I found regarding my above comment. I did indeed check temps with (Fluke equipment ISO 9001 in 2022) thermocouple inserted to the best of my ability 1/2 the way into the thickness of the pie(s) equivalent to 1/16" depth, and the temps were appx 400 degrees F. Keep in mind as you make the comparisons between potato chips and french fries, there is a factor of **TIME** involved here at a given temperature, **as there is in pizza.** Just because water can’t exist as a liquid above 212 degrees F is irrevelant in baking. Water is vaporized and then sequentially condensed and then re-vaporized over and over again within a given body of material (pizza) or french fries or potato chips.Given enough **TIME** all water will be removed and temperatures will increase to boil off remaining (usually oil) volatiles after which carbonization (burning) ensues. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [December 29, 2022, 4:39am UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/76 "2022-12-29T04:39:30Z")
The boiling point of water has minimal impact on the internal temperature of pizza, nor does the boiling point of water affect the ultimate temperature of pizza in general. Per Dominos website: Dominos oven technology is used to bake their pizzas at temperatures ranging from 600 to 800 degrees Fahrenheit up to 825 degrees Fahrenheit During the bake cycle, **the internal temperature of the pizza reaches up to 370°F,** with the outer crust reaching up to 600°F. Do you understand that there is a correlation between temperature, time and mass? Boil a quart pot of water… it doesn’t vaporize the instant it reaches 212 degrees F. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [December 29, 2022, 4:56am UTC](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224/77 "2022-12-29T04:56:45Z")
> [@ZurBob](#): > > Boil a quart pot of water… it doesn’t vaporize the instant it reaches 212 degrees F. No, but nor does it reach a temperature _higher_ than 212. That is the key point. There cannot be any water in the pizza at a temperature higher than 212. It may take some time for it to all evaporate, but only when it has all gone does the temperature rise. The latent heat of evaporation of water is huge. All the time the wet parts of the pizza is sitting in the oven with water in it, it is adsorbing energy that it uses to make the transition from liquid to gas. During this time the temperature does not rise. It is important in cooking to distinguish between “moist” due to water content and “moist” due to lipids. Lots of cooked things are reliant on fat to keep them “moist”. [Previous page](https://boards.straightdope.com/t/pizza-delivery-thermodynamics/975224.md?page=3)