Living in a dorm, I am severely limited by my cooking options. I have a non-microwave safe bowl, which I'm using for the noodle soup (that will be accompanied by said egg), and a highball glass.

There's a water dispenser which pours out hot water of exactly 70 degree C. If I fill up the glass with that, then after putting the egg in that glass, how long do I need to keep it there to make sure it's hard-boiled? (Note that I have no way to heat the water, so once it's poured into the glass and placed on the counter it'll start losing heat)

If a hard boiled egg isn't possible, a soft boiled will do. (as long as the egg doesn't remain gross in the whites or get me sick, I'm good)

  • Just wanted to comment that you can pour out the cooled water and replace them with new 70° water. Commented Oct 11, 2019 at 12:53
  • Good point. hadn't thought of that. So 70 is the highest I can go
    – rigel
    Commented Oct 11, 2019 at 12:54
  • Consider buying a portable hob, It can be as small as 20x20 cm, and will give you a lot of cooking options when combined with a single small pot. Hint: if a recipe is intended for a pan, it can usually be made in a pot too.
    – rumtscho
    Commented Oct 11, 2019 at 19:09
  • 1
    A sous vide circulation cooker might be an option? Get a bowl or pot, fill it up with water of any temperature, and insert the circulation cooker and plug it in. There's no flame, or exposed heating element. -- Also, consider you can buy pre-made hard-boiled eggs at most warehouse-style grocery stores pretty cheaply.
    – SnakeDoc
    Commented Oct 11, 2019 at 23:12
  • 2
    At least buy a microwave safe bowl (or microwave in the glass you've got). That will open up a lot of options
    – Chris H
    Commented Oct 12, 2019 at 11:56

2 Answers 2


In theory you should be able to reach your goal, sort of, borrowing from the Japanese Onsen egg and the Sous Vide technique. Serious Eats has an article detailing the results of slow-cooking eggs at different temperatures just around your given 70 C for further reference. You should aim to keep the water around the egg as high as possible and do so for the better part of an hour.
But let’s be honest - even with constant re-filling of 70C water you won’t end up with a solid egg and every degree lower will give you more and more watery whites - which I suspect you mean when you write “gross”. So while you can safely eat the egg, it remains to be seen whether you want to. And it’s a huge hassle, just for a soft egg.

But let me suggest an alternative, using the microwave you mentioned. Eggs in a microwave are doable, if you take the egg out of the shell. If you are really limited to a glass - assuming it’s a plain and reasonably heatproof one, otherwise it shouldn’t be used in your original setup either - use the glass. Pour about half a cup of water into the glass (or small bowl, if you can find one, for a nicer shape), add a generous sprinkle of salt. Crack your egg into the water and microwave the whole thing for about a minute to the desired doneness - no need to actually boil the water, actually you want to rather avoid boiling, but it’s not the end of the world if you do get bubbles. This should give you a nice poached egg. Zapp it a bit longer for a solid yolk. Of course, each microwave is different, so a bit of experimentation is in order, but this method should get you closer to your goal than the water dispenser one you were considering.


You cannot. 65 degrees Celsius is needed for sof boiled egg. I omitt the time as it don't play a role. For hard boiled you need higher temp to affect the yolk.
Now, you can't even make a soft boiled egg the way you describe as your water temparature will drastically drop after introducing egg (with assumed much lower temperature. Could be even 4 degrees if from fridge).
For boiling an egg you need constant supply of certain temperature. When you put an egg into water with a certain temperature without suppling the heat to keep that temp then the water temperature drops until it will be in equilibrium with surrounding one.

  • 1
    If the water is 70 degrees (and can be refreshed to keep it around that temp), and you only need 65 degrees for a soft boiled egg, then why is this impossible? It might take a long time, but it seems like it'd get there eventually.
    – Kat
    Commented Oct 11, 2019 at 20:40
  • @Kat Yes, eventually. That time might be after the egg becomes unedible.You might be able to make soft boiled with temp around 70. For hard boiled the transfer of energy might be not enough. Commented Oct 12, 2019 at 16:07

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