My wife use to put her insulated lunch bag in the refrigerator an hour or so before she left for work. I told her that the besides keeping the cold in, the bag also keeps the cold out and the stuff in her bag wasn’t going to get much colder. I proved this by putting a room temperature thermometer in the bag and putting it in the frig. In one hour, the temperature went from 72 degrees to 68. After 3 hours, it was down to 55. She started leaving the bag open, which helped some.
Is it true I shouldn't put a paper bag in the refrigerator because it will create a pocket of warm a
This reminds me of something that my wife says that always makes me raise an eyebrow.
I often stored things in the refrigerator that didn’t necessarily need to be stored there. But there was room and I wanted as little food in cabinets as possible.
When I got married, my wife would complain that there was no room to store things in the fridge because I had put ketchup bottles or other things that didn’t need to be there. I said, well, go ahead and take them out then.
Her reply is always “No, once something has been stored in the refrigerator, it has absorbed so much moisture that if you then move it to room temperature, it will spoil/grow fungus right away.”
That always sounded crazy to me, but she believes it so strongly that I can’t argue with her about it any more.
My guess is that this misconception arose in her family because when you open the refrigerator door, the difference between warm air outside and cool air inside causes some condensation on the packaging and they believed that this was proof that things in the fridge absorbed moisture.
What say you?
Put an open paper bag in the freezer overnight.
The next morning place it over your head and wear it all day as a portable air conditioner. After all, the paper is an excellent insulator and the cold air should last a long time. A well-known fact.
If you put something in a tupperware container, AND put the tupperware container in a paper bag, it will take longer to chill down than in just the bag, or just the tupperware (simply because two layers of insulation are more effective than one).
This might just possibly be a factor in cases where warm, high-risk food (let’s say half a container of leftover chinese takeaway) is placed in the fridge to chill down - if it’s double-insulated, it will stay in the warm ‘danger zone’ for longer.
Another factor is that, say, three containers of warm food, stacked together in *any *bag, will cool slower than if they were spread apart separately, but that’s not really the fault of the bag.
Finally, I guess some paper bags have more of a tendency to ‘tent’ than flimsy plastic, so the additional trapped air will increase the insulating effect.
However, I doubt any of these factors are very significant; certainly not enough to warrant a rule.
I’d have figured a closed paper bag would have some insulation value, but not a lot. Last time I was brown bagging, I had a small 6 pack sized cooler and 2 blue ice bricks. I’d put a brick and my lunch and beverage in the cooler and keep it in my locker till lunch time. When I got home, I’d put the brick in the freezer and use the other one the next day.
To pick on the particular example you offered, ketchup should be refrigerated after initial opening, but no need to do so when you bring it home from the grocery store. But as you described, “moisture absorption” has nothing to do with it; items that do not need refrigeration (but have been refrigerated anyway) can be safely removed from the fridge and stored at room temperature. Depending on ambient conditions they may temporarily develop condensation, but once they’ve warmed up, it’ll be like they were never refrigerated at all.
I’m sorry I just spent $ on a couple of lightweight frost blankets for the garden, when all I needed to do was pop a paper bag over tender plants to create a warm air “pocket”.
Could be a moneymaking idea there - sell paper bags painted green as frost protectors for those cold spring nights. The “Bag O’Hot Air” will make millions!
Not sure if this is snark or not but you COULD use paper bags! Milk Jug Hot Capsare a tradition in some parts of the country.
It’s not a bag of hot air and it’s not so much about insulation. It’s a contained volume that allows a small amount of heat to radiate from the earth and not be dispersed by winds. It works.
AIR is an excellent insulator and cold air will fall out of the inverted bag. A scientific fact. Tie it tighty around your neck and breathe through a straw 
Unfortunately, she’s partially right. It is true that a random object left in the refrigerator is probably growing fungus very very very slowly (at levels so low that you can’t even see it or smell it) and, when you move the item to a warm environment, the growth will speed up and the fungus will become visible relatively soon. This creates the illusion that taking it out of the refrigerator caused it to suddenly go bad. But the truth she’s overlooking is that it would have gone bad much sooner if you had never put it into the refrigerator in the first place.
But this has nothing to do with moisture. In fact, refrigerators tend to suck moisture out of things. When left in the open air in on a refrigerator shelf, bread gets hard and veggies wilt because they are losing moisture, not gaining it.
God NO!!!
You’ll let the bag’s warm air out into the rest of the refrigeration. You might as well take everything in the fridge and store them in the oven at 350.
Hmmm. What happens when you put a small oven into a large fridge, or vice versa?
Hmmm. A small oven OR a small air conditioner of the same wattage completely inside a large fridge would have the same effect!
Oddly enough, bread gets stale because it absorbs moisture. Yes, you can have dry bread, but stale bread and dry bread are two different things.
This is why stale bread can be rescued by toasting it–drive out the moisture and you get something edible.
The inside of your fridge is damper than your kitchen counter. But there’s the confounding effect that cold air doesn’t hold as much moisture as warm air. When I used to run a dehumidifier in the basement the bucket would fill up quickly on hot days, and very slowly on cold days, even though the cold days felt damper than the hot days.
So talking about how damp one environment is vs another can be tricky, because temperature makes a huge difference. But if you put damp rag in the fridge and one on the counter, the rag in the fridge will be damp days later, while the one on your counter will be dry. That isn’t to say that things can’t dry out in the fridge, veggies wilt because they dry out. But they would have dried out a lot faster on the countertop.
I’d think there could be an effect, especially on poorly sealed items. Going from cold to hot and the ensuing surface condensation could accelerate spoilage once being removed from the refrigerator.
I had a crazy as a loon supervisor a few years ago who used to wake up at 4AM and go to Walmart to do her family shopping. She’d then drive on into work and bring all the perishables inside and stick big bags of groceries in the break refrigerator. You’d go to put your lunch in there and there’d be a rump roast, 2 gallons of milk, and two dozen eggs taking up all the room. I’d’ve told her this tale (changing it to plastic bags) in a heartbeat if I thought she’d believe it. It would have worked if I’d had someone else tell her. She was pretty stupid, but she wouldn’t believe me if I said the sun was shinning in August.
The cold vs warm rag example as laid out here is a bit misleading. Yes, the countertop rag will be dry a day later while the fridge rag will take many days to dry out to a similar degree… but that’s got more to do with the relative volumes of open air around each rag than the temperatures of those air blocks. A better comparison would be if you put the rags in same-sized sealed containers - one in the fridge on and one the counter. Or put the second rag in an unplugged fridge to make the volumes of air around each rag available for moisture exchange to be the same. Sure the warm rag will dry out more and faster, but the differences in time would be a lot less dramatic than when the cold rag is in a small confined area while the warm rag has a much larger area for it’s moisture to evaporate into.
A well known fact:
People get the dumbs when discussing thermodynamics and refrigerators.
My teacher friend didn’t believe me that the covered butter compartment was warmer than the remainder of the fridge. This is the same person who insisted that there was benefit in putting a room temperature beer in a room temperature cooler. If you’re bad at imagining a complete system, you’re going to be bad at predicting heat’s movements.
Yes, but we’re discussing how damp your fridge is. The fridge is a confined environment that traps moisture, agreed. Your countertop isn’t, agreed. But that’s te point! Any moisture in your fridge is going to be tapped inside and stay there and moisten stuff. Bread in the fridge doesn’t get stale because the fridge is so dry, it gets stale because the fridge is moist, and moisture causes staleness. The same bread left on the counter will get stale more slowly, because it is drier.
So you’re right that there are two factors involved here, the temperature and the sealed fridge.
Yep. Thermo is cool. Some of my favorite college courses. Everything works out.
!st Law of Thermodynamics - You can’t win. 
2nd Law of Thermodynamics - You can’t even break even!!
If one doesn’t see the truth in this you don’t really know thermo… 