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Name: Annette
Status: other
Grade: 3-6
Location: LA
Country: USA
Date: Winter 2012-2013


Question:
I am helping my grandson with an experiment on growing crystals from granulated sugar, brown sugar and powdered sugar. We found that the granulated sugar worked best. I cannot find out why this sugar works best. We found that brown sugar and powdered sugar contain additives. Could this be why?



Replies:
Annette,

Yes, you are correct in thinking that the additives in brown and powdered sugar have something to do with the additives. Brown sugar is un refined evaporated juice extract - so it contains other substances that were in the plant extract. Powdered sugar has some kind of starch (usually corn starch) to give it the desired consistency. In both these cases the extra ingredients will inhibit crystal growth either by reducing the amount of sugar that can be dissolved in the water - the same amount placed into water will contain less sugar, or by disturbing (changing the crystal pattern, adding impurities to the crystal, reducing the crystallization temperature, etc.) the crystallization pattern.

Greg (Roberto Gregorius) Canisius College


Hi Annette,

Thanks for the good question. Granulated sugar and powdered sugar should work (roughly) the same for growing crystals. Could you please let me know what additives your brown sugar and powdered sugar contain? Generally speaking, the purer the sugar you start with, the better quality of crystals you obtain. By "quality", I am referring to size and clarity of the crystals. Impurities and additives will interfere with the crystal growing process by becoming trapped in the crystal. This trapping causes the crystal to grow smaller and have lower clarity. The same concepts also apply to the formation of diamonds, by the way.

I hope this helps. Please let me know if you have any other questions. Thanks Jeff Grell


Brown sugar and powdered sugar contain additives – molasses in the case of brown sugar and some type of anti-caking sugar in the case of powdered sugar. If you do a Google search on these types of sugar you will find sites that discuss the additives in detail. “Regular” sugar contains relatively small amounts of additives. That is why it forms crystals more readily. The topic is too complicated to discuss in detail here, but the web sites go into detail.

Vince Calder


I think you have discovered the reason, but not the mechanism. Brown sugar and powdered sugar do contain additives. What additives and how much differs in either case. Brown sugar contains molasses. Powdered sugar contains anti-caking agents (see:

http://en.wikipedia.org/wiki/Anti-caking_agent

). You can find details by doing a Google search on each type of sugar. In any case, crystallization is a very sensitive complex process affected by many factors, especially by the presence of additives.

Vince Calder


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