This is what my dad used to do, dig a small hole in the back garden when the weather started getting warmer. It was about a foot deep and a foot square. Mum placed the milk bottles therein, which were always beaded with condensation, even on a warm summer's day.
What's the science behind this?
MM
Probably a combination of preventing the sun getting to it and dampness in the earth . I take it you didn't have a fridge . Stuart
yes, plus very large thermal storage and plus grass evaporating water off, which causes cooling.
NT
That just means they're relatively cooler than the air, not that they're cool in absolute terms.
Pit coolers and swamp coolers are combination of several things.
Firstly pits don't really "cool" anything, they just avoid the peak temperatures of the hottest part of the day. Overall (including the night) the average temperature is much lower. Many food-spoiling processes are more susceptible to a high short peak exceeding some threshold than to the average. If you sink the pit into a well- insulated mass with a high thermal inertia (a well-lidded soil pit does both) then a mere milk bottle will remain at the soil's seasonal average, not climb to the daytime temperature.
Make a hole the size of a shed, line it with straw and you can keep ice into the Summer. Many 18th century ice-houses still survive today.
It takes energy to evaporate a liquid, which is the principle behind the swamp cooler. Take a pool of water with a large wick in it and it will drop in temperature as the water evaporates into the passing drier air. Make a permeable terracotta pot, fill it with water and you have a traditional butter cooler. It needs airflow though, so it's more of an alternative to the pit than an addition to it. Handy for camping though.
Correct. We didn't have a fridge till the 1960s.
MM
Interesting! Especially the butter cooler idea.
MM
Same way as a pubs cellar works - it's part of the Free underground air considitioning system
=============================== Butter coolers of this type were very common at one time. Try your local church jumble sale to find one.
p.s. You can reverse the principle (i.e. keep things warm) by creating a 'haybox'. Line a large box (including a lid) with hay / straw and put a hot casserole inside and it will stay warm or even continue cooking. Slow cookers use the same principle, I believe.
Cic.
Handy for picnic wine cooling too
In S Africa, you used to see people driving around with hessian bags of beer cans tied to the door mirrors..a douse of water once every few miles kept them cool by evaporation.
I used to have a cooler which looked like a 'fridge, it was made of some kind of plaster like stuff which you soaked in a stream or with a hosepipe, it would keep milk fresh over a long weekend providing you kept it watered.
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