Thread by @nickmmark

Yesterday I shared a fun fact that black coffee cools faster than coffee with milk/cream.

https://twitter.com/nickmmark/status/1445372568152653830?s=21

Today I woke up early and decided to do an experiment. What followed was interesting & more than a little messy (🤷 that’s science!)

A short 🧵 on ☕️ science
1/

First some background:

Supposedly black coffee ☕️ cools faster for two reasons:
1. Black coffee radiates more heat because black objects have greater emissivity (due to Stefan Boltzmann)
2. Milk 🥛 increases viscosity & decrease evaporative cooling

Should be easy to test?
2/

Methods:
I made coffee & (tried to) warm the 🥛 to the same temperature as the ☕️.

I aliquoted the coffee and combined w/ or w/o 50 ml milk, bringing to the same volume (250ml).

Then I tried to pour both simultaneously into identical cups but managed to make a big mess. 🙊
3/

I monitored surface temperature of the coffee in both cups continuously using a consumer grade iPhone thermal camera 📷

I recorded temp manually every minute. If you have a free app or python code to scrape text from video, please share 🙏; this is what I whipped up at 5:30am
4/

Results:
Very interesting…🤔

I messed up the🥛temp (I think it cooled while I was cleaning up spilled ☕️ ) so the two cups started off at slightly different temperatures(45 vs 40°C)

Despite this the RATE of cooling appeared slightly faster in black☕️ (0.34 vs 0.25°C/min)🧐
5/

Limitations:
-I conceived of & did this whole experiment in 45 minutes starting at 5:30am (before my kids woke up)
-it’s very hard to watch a perfectly good cup of ☕️ get cold
-I’m clearly no barista & I messed up the🥛 temp & ☕️ pour
-an n=1 experiment isn’t very meaningful!
6/

Conclusion:
- based on a rapidly conceived & poorly executed kitchen experiment performed once while fatigued, I conclude that black ☕️ may indeed cool faster than ☕️ with milk.
- I look forward to being excoriated by reviewer #2
- please DO try this experiment at home!
7/7