# Why do the cubes from the bottom ice cube tray never come out as easy as the ones from the top? **URL:** \ **Category:** Factual Questions\ **Created:** [June 7, 2014, 11:12pm UTC](https://boards.straightdope.com/t/why-do-the-cubes-from-the-bottom-ice-cube-tray-never-come-out-as-easy-as-the-ones-from-the-top/690302 "2014-06-07T23:12:18Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Revtim](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/revtim/32/1042_2.png) [@Revtim](https://boards.straightdope.com/u/Revtim)\ **Post date:** [June 7, 2014, 11:12pm UTC](https://boards.straightdope.com/t/why-do-the-cubes-from-the-bottom-ice-cube-tray-never-come-out-as-easy-as-the-ones-from-the-top/690302/1 "2014-06-07T23:12:18Z")
I alternate which tray is on the bottom each time, with the bottom cubes always breaking and shattering, so it’s not a physical difference in the tray. This was actually asked here before, 12 years ago: > **[Ice-cube tray question...](https://boards.straightdope.com/sdmb/showthread.php?t=127934)** > > We recently got a new fridge, without an icemaker :eek:, luckily, I found the recipe for ice cubes on the 'net, and have been making them in plastic trays. My question is, when I fill two trays with water and stack them, the cubes in the bottom tray... No definitive answer. Perhaps the top ones freeze quicker? Would that make a difference? ---
**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:** [June 7, 2014, 11:56pm UTC](https://boards.straightdope.com/t/why-do-the-cubes-from-the-bottom-ice-cube-tray-never-come-out-as-easy-as-the-ones-from-the-top/690302/2 "2014-06-07T23:56:59Z")
Maybe the bottom try is a bit colder. The top one therefore is just a few degrees ahead in warming up as you take it out creating a small amount of melt between the cubes and the tray while the colder lower tray is more solidly frozen? Try waiting an extra minute or so before taking cubes out of the bottom tray and let us know if it makes a difference. ---
**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:** [June 8, 2014, 12:03am UTC](https://boards.straightdope.com/t/why-do-the-cubes-from-the-bottom-ice-cube-tray-never-come-out-as-easy-as-the-ones-from-the-top/690302/3 "2014-06-08T00:03:55Z")
However a quick search gives [this answer](http://physics.stackexchange.com/questions/21942/why-do-ice-cubes-come-out-easier-from-top-trays), which makes more sense than my WAG: > [@](#): > > Ice expands as it freezes. So, if freezing starts at the top surface of the water, the liquid water below it allows the cube to edge gently upwards as it freezes, without much stress on it. This same upwards edging effect also keeps the ice from every gaining a solid hold on the entire surface of the tray. Result: The top surface of the ice cube stays flat, and the cube comes out of the tray easily without cracking. > > Conversely, if freezing starts from below at the tray surface, the freezing water has the time and opportunity to lock itself tightly to all parts of that surface. But as the ice continues to grow inward, it tries to expand from all sides at once into the internal space. This creates a lot of stress in the ice, and causes the cube to form a peak at the top due to the internally expanding ice having no place else to go. So, since the ice has both had ample opportunity to freeze tightly to all of the tray surface, and because it was stressed internally as the freezing progressed, the ice cube becomes a disaster when you try to get it out. Much of it sticks to the tray, and the parts that do come out are often cracked. > > How is all of this connected to whether a tray is stacked on top or bottom? > > It’s because stacked trays almost always impedes the cold air of the freezer from getting between the trays. That causes the stacked trays to behave largely like a single unit, with freezing occurring from the outside of that two-tray unit. The top tray therefore freezes mostly from the top down, producing ice cubes that have flat surfaces and come out easily. The bottom tray freezes mostly from the bottom up through the surface of the tray, and so ends up producing peaked ice cubes that stick to the tray and crack when you try to remove them. Check to see if the bottom tray’s cubes are peaked compared to flat-topped upper tray cubes. ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [June 8, 2014, 12:32am UTC](https://boards.straightdope.com/t/why-do-the-cubes-from-the-bottom-ice-cube-tray-never-come-out-as-easy-as-the-ones-from-the-top/690302/4 "2014-06-08T00:32:27Z")
> [@Revtim](#): > > I alternate which tray is on the bottom each time, with the bottom cubes always breaking and shattering, so it’s not a physical difference in the tray. I alternate which tray is on the bottom each time, with the **top** cubes always breaking and shattering, so it’s not a physical difference in the tray. In this case I only have 2 trays (I suppose I could expand it) and they’re in the bottom left front of a top freezer. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [June 8, 2014, 1:41am UTC](https://boards.straightdope.com/t/why-do-the-cubes-from-the-bottom-ice-cube-tray-never-come-out-as-easy-as-the-ones-from-the-top/690302/5 "2014-06-08T01:41:14Z")
some of the cracking is the cube not releasing from the tray and fracturing. warming the tray and dividers might help. ---
**Author:** ![Tim\_R.Mortiss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tim_r.mortiss/32/142_2.png) [@Tim\_R.Mortiss](https://boards.straightdope.com/u/Tim_R.Mortiss)\ **Post date:** [June 8, 2014, 2:25am UTC](https://boards.straightdope.com/t/why-do-the-cubes-from-the-bottom-ice-cube-tray-never-come-out-as-easy-as-the-ones-from-the-top/690302/6 "2014-06-08T02:25:21Z")
I don’t have an answer, but my observation agrees with that of **revtim** : the bottom tray is always harder to get the ice out, while the cubes in the top tray pop out nice and clean.