Sciencemadness Discussion Board

How to grow crystals & Why do they form?

Yttrium2 - 3-7-2020 at 14:25

I faintly remember way back in science class we had grown sugar crystals on a string.


I am wondering, how does one grow crystals?


I want to try this with sugar, also, how can I grow them on a string and why do they form as opposed to granulated sugar touching itself without the water present?


Is this how all or most crystals are formed?




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I'm guessing you have to form a super saturated solution, and allow it too cool, but will this work?


How can I form crystals instead of a scum film around the crystallization dish?

I'd like to make big crystals, instead of tiny little ones

[Edited on 7/3/2020 by Yttrium2]

Abromination - 3-7-2020 at 15:45

You will waste much less time using google then asking to be spoonfed trivial questions. Few here have the patience to answer these questions. The process is extremely simple and will be more educational if you do the research yourself.

Bedlasky - 3-7-2020 at 16:53

This website is good source of informations about crystal growing:

https://en.crystalls.info/Welcome

Yttrium2 - 3-7-2020 at 17:34

I think I got it right, form the supersaturated solution and let it cool.


I noticed a difference in the crystal shape of the stuff made in 4 hours, from the crystals that took time to develop over several days.

Can't you make the nicer looking crystals quickly aswell?


What happens when the supersaturated solution of sugar cools? It forms a precipitate, but is it in a good, nice looking, crystalline form?

Ubya - 3-7-2020 at 18:41

Quote: Originally posted by Yttrium2  
I think I got it right, form the supersaturated solution and let it cool.


I noticed a difference in the crystal shape of the stuff made in 4 hours, from the crystals that took time to develop over several days.

Can't you make the nicer looking crystals quickly aswell?


What happens when the supersaturated solution of sugar cools? It forms a precipitate, but is it in a good, nice looking, crystalline form?


under the microscope they are good or perfect crystals? but most of the time you want big crystals.

the difference in shape can be caused by different crystal structures more stable at different temperature, like sulphur.

DraconicAcid - 3-7-2020 at 18:44

No, you can't make nice-looking crystals quickly. The more slowly they grow, the better crystals you get.

B(a)P - 4-7-2020 at 01:19

There are huge amounts of information on the web about this subject.
One tip is to use changes in concentration at a constant temperature rather than temperature changes to grow larger crystals.
Make a near concentrated solution then place a seed crystal in it and let the crystal develop as the solution evaporates. This is much slower and as a result grows much larger crystals.

Eddie Current - 4-7-2020 at 04:39

Quote: Originally posted by Yttrium2  
Why do they form?


Whoever can answer this correctly, will probably win the Nobel Prize.

Yttrium2 - 4-7-2020 at 09:05

What about melting the stuff down, will this produce a crystal that can then be chipped out of the beaker?


With sugar my guess is no, since it turns into carmel, but does it have a melting point?

[Edited on 7/4/2020 by Yttrium2]

SWIM - 4-7-2020 at 09:41


No, but It'll make your desserts look dramatic.



[Edited on 4-7-2020 by SWIM]

yttriumcrystals.jpg - 8kB
The melting point, for sucrose, at least, is very close to the decomposition point.
It's hard to melt it in any quantity without decomposition.



[Edited on 4-7-2020 by SWIM]

Cou - 4-7-2020 at 13:38

Wikipedia is also a good resource.
https://en.wikipedia.org/wiki/Crystal

Twospoons - 4-7-2020 at 14:09

Another method: Hydrothermal

Good for growing large crystals quickly. Another advantage is that you don't get a 'crust' forming at the top of the liquid - which can sometimes break off and mess up an otherwise nice crystal.

Also good for systems where the solvent is expensive, or toxic, or stinky, as its a closed system.

Growth rate can also be readily controlled by changing the temperature differential.

Yttrium2 - 4-7-2020 at 14:26

that is a beautiful crystal two spoons, I was also thinking of growing the copper salt crystals.


I didnt understand what the hydrothermal method was based on your post though, by the sounds of it, it sounds like one needs pressure.

Twospoons - 4-7-2020 at 18:16

No pressure isn't a requirement, at least for most ionic salts. The idea is to create a thermal gradient, with bulk material at the warm end. This results in a concentration gradient, and a steady diffusion of dissolved material to the cool end where it deposits on the growing crystal.

The reason pressure was mentioned is because growing quartz crystals requires the solution to be very hot (~250 to 300 C), which can only be achieved under high pressures (~10bar).

[Edited on 5-7-2020 by Twospoons]