# Creating Dry Ice **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [August 24, 2003, 11:12am UTC](https://boards.straightdope.com/t/creating-dry-ice/197309 "2003-08-24T11:12:27Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![mindputty](https://avatars.discourse-cdn.com/v4/letter/m/ac91a4/32.png) [@mindputty](https://boards.straightdope.com/u/mindputty)\ **Post date:** [August 24, 2003, 11:12am UTC](https://boards.straightdope.com/t/creating-dry-ice/197309/1 "2003-08-24T11:12:27Z")
The Dry Ice article was very informative and interesting. However, it still remains to be asked - how exactly is Dry Ice created? Do you simply take a bunch of CO2 floating around in a box and make it really cold - at which point it flashes into ice? What would an observer see as it was being made? The link: [http://www.straightdope.com/mailbag/mdryice.html](http://www.straightdope.com/mailbag/mdryice.html) ---
**Author:** ![Ice\_Wolf](https://avatars.discourse-cdn.com/v4/letter/i/dfb087/32.png) [@Ice\_Wolf](https://boards.straightdope.com/u/Ice_Wolf)\ **Post date:** [August 24, 2003, 11:21am UTC](https://boards.straightdope.com/t/creating-dry-ice/197309/2 "2003-08-24T11:21:00Z")
[From this site:](http://www.occc.com/abc/dry-ice.htm) Compress the CO2, remove excess heat, send through an expansion valve, then compress the flakes into a block. ---
**Author:** ![mindputty](https://avatars.discourse-cdn.com/v4/letter/m/ac91a4/32.png) [@mindputty](https://boards.straightdope.com/u/mindputty)\ **Post date:** [August 24, 2003, 8:00pm UTC](https://boards.straightdope.com/t/creating-dry-ice/197309/3 "2003-08-24T20:00:31Z")
Thanks for the reply, Ice Wolf. One thing about the explanation given at the site you recommend baffles me: how does absorption of heat by the evaporating liquid cause it to freeze? Generally, doesn’t the addition of heat do the opposite - that is, melt (or in this case sublimate) a substance? I continue to harbour a vision of a room full of CO2 in which golf ball-sized chunks of ice materialize in thin air and fall to the ground. 🙂 ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [August 24, 2003, 8:18pm UTC](https://boards.straightdope.com/t/creating-dry-ice/197309/4 "2003-08-24T20:18:58Z")
You can make your own dry ice from compressed CO[sub]2[/sub] in a tank with [this device](http://scientificsonline.com/product.asp?pn=3071533) from Edmund Scientific. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [August 25, 2003, 3:59am UTC](https://boards.straightdope.com/t/creating-dry-ice/197309/5 "2003-08-25T03:59:14Z")
**mindputty** , the outgassing CO2 is removing heat from the liquid part left behind. The standard evaporative chilling effect. Perhaps “absorbs heat” isn’t the best phrase the cited article could have used. ---
**Author:** ![mindputty](https://avatars.discourse-cdn.com/v4/letter/m/ac91a4/32.png) [@mindputty](https://boards.straightdope.com/u/mindputty)\ **Post date:** [August 25, 2003, 7:30am UTC](https://boards.straightdope.com/t/creating-dry-ice/197309/6 "2003-08-25T07:30:21Z")
Aha. Gotcha. I was confused there for a while - I got hung up on the notion that dry ice is a solid gas. In actuality, it’s the compressed liquid that is changing into the solid ice flakes, not the evaporating gas, correct? Could that ever happen? That is, a gas going directly to a solid state? That would be fascinating. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [August 25, 2003, 5:36pm UTC](https://boards.straightdope.com/t/creating-dry-ice/197309/7 "2003-08-25T17:36:49Z")
Gaseous CO[sub]2[/sub] will indeed go directly to a solid, at standard pressure and sufficiently low temperature. It’s just that the easiest way to get such temperatures involves pressurizing it first. If, say, you took a sealed container of gaseous CO[sub]2[/sub] (at STP) and dunked it into a resevoir of liquid nitrogen, the gas in the container would go directly to a solid. In this case, I imagine that it would deposit like frost on the walls of the container. For that matter, I think that ordinary water frost is also an example of transition directly from gas to solid.