Crystals are formed when atoms line up in patterns and solidify.  There are crystals everywhere — in the form of salt, sugar, sand, diamonds, quartz, and many more!


To make crystals, you need to make a very special kind of solution called a supersaturated solid solution.  Here’s what that means: if you add salt by the spoonful to a cup of water, you’ll reach a point where the salt doesn’t disappear (dissolve) anymore and forms a lump at the bottom of the glass.


The point at which it begins to form a lump is just past the point of saturation. If you heat up the saltwater, the lump disappears.  You can now add more and more salt, until it can’t take any more (you’ll see another lump starting to form at the bottom).  This is now a supersaturated solid solution.  Mix in a bit of water to make the lump disappear.  Your solution is ready for making crystals.  But how?


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79 Responses to “Rock Candy Crystals”

  1. You should see some growth within 2 days. The growth can be helped along by adding the hsugar “seeds” as shown in the video. We don’t recommend adding flavors because those additional chemicals can affect how the sugar molecules bond.

  2. kristy_craig says:

    Hey, this is Liam, and I was wondering how long does it take. because in the video you said day, week, months, 6 months” witch one? Can I add flavors to it, like extracts? Like root bear, villania, almond, green apple, and others.
    Thank you!

  3. rebecca_hyink says:

    Hi, Aurora.
    This is Nina,Rebecca’s daughter. I have been doing Supercharged Science for four months,and I have really enjoyed it! I can’t wait to make some rock candy!

  4. Yes this is one of the FEW that you can! Enjoy!

  5. Brett Barkley says:

    Can you eat this stuff??

  6. My hunch would be that the second jar that you filled is forming more crystals. This is because there was probably more sugar settled into the bottom of the pan.

    You can try it again and label the jars to see if you see the same results!

  7. we made two jars full a couple of days ago and one of them isn’t growing but both jars contained the same water and sugar mixture in the same pot. what happened?????????????? :l

  8. Plus, why does it take so long for the sugar to melt into a solution?

  9. I cant wait to see them in six months but why does it take ssssooooooooo long for them to form????

  10. Coconut sugar should work! Please let us know how it turns out for you.

  11. ERICA KASSNER says:

    Hi again! Can we use coconut sugar for this experiment or does it need to be cane sugar?

  12. Hertha McLendon says:

    I’m exited to make the rock candy crystals !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! I wonder what they’ll taste like ?????????????????????????????????????????????????????????????????????????

  13. Yes you can! I accidentally left my digital thermometer probe in my sample last week that I was doing with my students so we could monitor when the temperature was below 135 degrees F, and then we got sidetracked doing other experiments and when I came back the next day, the entire metal skewer-looking probe was covered in crystals! 🙂 Just give it a try and see what happens to yours. We warmed ours up again and added more water because we had too much sugar – it crystallized way too fast.

  14. Areeg Abbasi says:

    Can we use a metal skewer?

  15. I don’t think so, but… I want you to try it and then tell me how it works for you. (It’s got a totally different crystal structure.)

  16. Paula Madigan says:

    Can we use stevia instead of sugar?

    Justine

  17. Wow – I never thought of that… try it and tell me!

  18. Michelle Stevens says:

    If you add some fruit juice to the water will your rock candy crystals be flavored?

  19. Hi Earnest! What was in your water before you added the sugar?

  20. Hi my name is Earnest
    There is a white layer that floats on above the sugar solution.Can you please tell me what it is?

  21. Irenio and Deena Mateo says:

    uuuh… is whoopsy the right word?

  22. If you just add sugar to water, you’ll get a clump of sugar at the bottom since the water’s ability to absorb the sugar is pretty low. If you heat the solution to nearly boiling and there’s still some at the bottom, then it’s super saturated. Separate out the the liquid into a clean jar and don’t let the stuff and the bottom go into your clean jar, or it will trigger massive crystals so large you will have a geode instead of a rock candy stick. 🙂

  23. Irenio and Deena Mateo says:

    is the sugar supposed to settle in the jar? My sugar has settled at the bottom.

  24. Well you can try to kill it (“die”), but coloring it (“dye”) might be more fun. 🙂

  25. Laura Swick says:

    is it okay if you die the rock candy

    Moira 8

  26. Mimi Snider says:

    pretty cool Boaz 🙂

  27. Yes, put it back on the stove and add more sugar to the heated solution. You should see crystals within 24-48 hours.

  28. Mia Rodriguez says:

    I think i did not add enough sugar to my water because it had been almost a week and i have not seen any crystals. Can i take the my solution and reheat it and add more sugar or should i start over?
    Thanks

  29. Mia Rodriguez says:

    Thanks

  30. Yes, you can halve the recipe – just be sure to add as much sugar as possible before you start cooling the solution. If it’s colder, then not all the sugar will get suspended in the solution. Hotter is better than colder.

  31. Mia Rodriguez says:

    Dear Aurora,
    Is it okay if I half the water and the sugar so that it is 1 1/2 cup of water and 4 cups of sugar? And when I put my solution in the jar does it have to be 130 degrees and can it be colder or hotter?

    Thanks

  32. No, it will be more saturated, which means that the crystals will solidify not only on the stick, but to the walls, and if you add too much sugar, it will look like all the liquid turned solid.

  33. Natasha Omdahl says:

    If you add more sugar would the process be faster?

  34. Sharon Wu says:

    How do you make it colored??
    Zach 🙂

  35. It sounds like there wasn’t enough water in your solution. You can empty out the remaining liquid back into the pan, and fill the container with plain water to dissolve the crystals (you’ll have to leave it overnight). Then come back and pour this solution also back into the pan. Add a little more of the sugar and bring it back to a boil and try again. I know you can do it!

  36. Shiralee Seerden says:

    mine turned soiled what is wrong with this

    samuel ;] ;/ ;[

  37. jennifer lutz says:

    how does it work

  38. Yes, you can certainly do it in smaller jars, but you’ll have to really make sure that solution is very saturated. Test it out before giving it the kids so you can make any adjustments ahead of time. If this is your first time doing this, you’ll want to do a run-though beforehand, since getting the solution right can be tricky.

  39. Tara Romsaithong says:

    We will be doing this in January in our co-op. We have 3 classes ranging in size from 8 to 12 children. If we want to let each child have a rock candy stick, how much do you think we should use? I was planning on using old jelly jars, to give you an idea of approximate size. Thanks!

  40. Hmmm… sounds like you have an over-saturated solution, because if none of the crystals formed on the stick and only at the bottom, which tells me that some of the sugar was at the bottom (and not dissolved in the solution) – the bits may have been super-small, but you can tell they were still there if you see the crystals growing only at the bottom. Dump the solution (with as many of the bottom crystals as you can scrape out) back into the saucepan and add a little more water, stirring until everything dissolves and then try again. You can divide the solution into smaller cups and add different amounts of water to figure out how much is the right amount – that in itself is a great way to show how to do real science!

  41. Caroline Wood says:

    The kids, for some strange reason, really want this experiment to work. Now , it is crystallising fine but all the crystals are at the bottom of the jar!! They want me to ask you why. we did make sure the stick wasn’t touching the bottom.

  42. When you dissolve sugar (or anything else) in water, the solute (that’s the sugar in this case) dissociates. That basically means it breaks apart. While the solute is breaking apart, you can still see it. This is the cloudiness you observed. Once the sugar is fully dissolved, you have a solution. A solution means the solute is evenly spread out. At that point, the water looks clear. Of course, the sugar is still there, and the solution would taste sweet if you drank it. The solute has just become invisible.

  43. Luc Pegram says:

    Dear Aurora,
    A question: Please explain why the solution looked cloudy at first so much so we couldn’t see the bottom of the pot. This was while it was heating and then after cooling for a while minutes the solution cleared and we could see the bottom of the pot. What was happening to our solution?
    Luc 11

  44. Yes as long as it’s edible-quality if you are planning to eat your creation.

  45. Sophia Pitcher says:

    Can we eat this??? ~jasmin

  46. Sophia Pitcher says:

    Can you use food coloring gel? Isabel Pitcher

  47. Sandra Sires Kraha says:

    This is a really fun project to do I love it.
    From Jasmine Kraha

  48. Sylvia Huynh says:

    Dear Aurora,

    They turned out awesome! My 8 yr old daughter and 5 yr old son thinks it’s so cool. Thank you for making science much more interesting and easy to understand for them.

    Now I noticed, I had poured out 3 separate jars, 2 tall ones and 1 shorter one. The shorter one grew the fastest and most. The 1st tall jar had big visible crystals but not too many.

    The 2nd taller jar didn’t form sign of crystals, so I decided to take it out and sprinkle more sugar on the straw (instead of a skewer.) Stuck it back in the jar and a few days later, crystals started to grow. This particular jar was more cloudy is it because too much of the sugar were in the jar and dropped from the straw? Thanks.

  49. Juliet White says:

    I’m going to try that out.

  50. No, there’s not much difference between using powdered or granulated sugar when making this project – I tried both and got the same results.

  51. Sounds like you had too much sugar and not enough water. Put everything back into the pot and add a bit of water (less than a cup) and try again. It takes patience to get this one right – however it’s completely reversible, so if you try it and nothing happens, then you know you need more sugar. If you try it and it solidifies too fast, you know you have too much sugar. Does that make sense?

  52. Sophia Poli says:

    would it have worked better if I used powetered sugar????
    thank you

  53. Sophia Poli says:

    Could you tell me what I was doing wrong?? I started with 3 cups sugar and 3 cups water and i worked up to 7 and it would not dissolve I had the stove on the entier time, and I heated it up to 200 so not boiling but cloce like you said. I split the batch in to 5 cups and they all got completly hard within 12 houres. HELP ME!!

  54. Wonderful! And yes, your crystals will continue to grow as long as there’s saturated solution in the jar. However, you might not notice the crystal growth as much when the crystals are larger than when they first started out. If you really want to speed up the process, empty out the solution and add fresh solution to the jar to continue the growth. This is especially fun to do with multiple colors layered on top of each other, darkest being in the center.

  55. Anonymous says:

    Well, it’s been 3 weeks of waiting and watching our sugar crystals and we are excited to announce that they turned out great!!! We don’t even have them in a warm spot. They are just sitting on our kitchen counter, not in the sun. We did 4 separate jars. One we left open on the top which we just used the string and paper clip. 2 in jars with the lid partially on using skewers. And one in a jar with a skewer that has been closed most of the time besides our frequent checking on it. The results show that there was little difference in the jars with the lids and skewers but the open stringed candy is kind of crazy looking as it formed bigger crystal chunks. I’m guessing the other jars weren’t getting enough evaporation going on but they look way nicer and even. Ours look almost as big as your picture of the 6 month old crystals. Will they continue to grow? It doesn’t seem like they are changing any more. Maybe we need to just move them to a warmer spot?

  56. The superfine sugar will dissolve more readily, so you’re going to get a saturated solution more quickly than with regular sugar. So good work there! The bits on the top of the jars is normal – however if they get too thick, just crack them and remove them as they form, as they keep the water from evaporating (which is what you want). It sounds like you did a great job! 🙂

  57. Anonymous says:

    I did this with 6 kids today and I’m not sure what the outcome will be. My husband came home with a 25 lb bag of superfine sugar for us to use and we used all of it!!! I think it dissolved too quickly and we couldn’t tell if there was any bits on the bottom. I had thought we would need 3 cups of water for each kids so this turned out to be a really huge batch. And as we added the sugar the water was multiplying. I didn’t expect that at all. So in the end we ended up with more than twice as much solution than we needed. If we already see bits on the top of the jars, should we add a bit more water? Also, do you think the superfine sugar versus regular sugar will make a difference?

  58. If you try to make rock candy from raw sugar or brown sugar, it’ll be golden or brown and have a different taste than made from white (refined) sugar. Brown sugar is basically white sugar with a tiny layer of molasses covering each grain of sugar.

    The amounts of sugar and water are different, so add enough sugar to mix up a saturated solution and continue as directed in the project. You should see results in 3-7 days, provided your solution is saturated enough (you’ll notice a crust forming on day 1 or 2 – this tells you that you’re on track).

    Flavoring idea: You can also pop in a lifesavers candy into the pot as you heat the solution – it will melt and flavor your rock candy.

    Note – the biggest problem people have with rock candy projects is that they didn’t add enough sugar. You need WAY more sugar than water for this experiment to work!

  59. No, humidity doesn’t play a role when the crystals are already submerged in a solution. The laundry room should work great. Let me know how it goes.

  60. Debra Thomson says:

    I just got an idea for a flavored rock candy stick. What if I replaced white sugar with brown sugar? Have you tried this before? If so, how did it turn out? Do you think this would still be successful, or not so much?
    Thanks!
    -Steph

  61. Debra Thomson says:

    You say to put the solution in a warm place while waiting for the crystals to grow…does humidity make a difference, though? I was thinking I could put it in our laundry room, since that room is typically the warmest one in the house. But it also tends to get humid, due to lack of ventilation. Would this slow the crystals’ growing time?

  62. Hmmm… sounds like your solution is not quite right. Did you ‘seed’ the stick? Drag a wet stick through a pile of sugar and then stick it in the jar (don’t worry if some fall off in the solution.

    If your solution gets cold, it will slow the crystal-growth slower than a snail’s pace. Try keeping it on a heating pad or up on a high shelf in a warm spot in your house.

    If you think you don’t have a saturated solution, dump the contents back into a pan, heat it up, and add more sugar. Keep adding sugar to your near-boiling solution until you can’t add any more… they only sit at the bottom and refuse to vanish. That’s when you know you’ve got it. Keep me posted!

  63. Amy Bowman says:

    We made a super-saturated solution the first time we triedthis and the entire jar-full of it started to crystalize so we had to reheat it and add a little more water while we could still get it out of the jar. We couldn’t get all of it out of the jar because some of the bigger crystals were stuck to the bottom. We didn’tadd much more water, maybe a third of a cup in the end (we also had to add moresugar, though) and then when we poured itback into the jars andmanaged to desolve the crystals on the bottom. Now it’s been at least 2 weeks and we can’t even see small crystals at all. We halved the recipe and Ithink weactually used MORE sugar than itsaid wewouldneed, so natrally we’reconfused. We’vebeen keepingitoveer our gas firplace because that is the only warm spotin ourhouse rightnow,andit’son mostof the time and can sometimesgetsort of hot. What have we done wrong? Couldtherebe any reason why wedon’t haveany crystals yet other than havingtoo much water in thesolution? The tempuraturebythe fireplacevariesa lot, probably from 69-85 F. Thanks! 🙂

    ~Anna,12

    p.s. Sorry about all of the typos, ourkeyboardisn’t working well.

  64. sevy keble says:

    Yea! After 3 weeks our crystals FINALLY grew. OH YEAH!
    sevy keble 🙂

  65. Yes, you should try the salt and sugar and time it. To keep your variables to a minimum, though, make saturated solutions of each one (dissolve as much solids as you can into each one until you see little undissolved bits at the bottom). The amount of salt-to-water and sugar-to-water will not be the same, but that’s okay.

  66. Some plastics leech out chemicals when you add certain liquids to them, especially if they’re hot – not good if you plan to eat these crystals. Watch out for the cracking with glass, though – wait until it reaches hot tap water temp before pouring it into the jar.

  67. Too much sugar means that you’d get crystals sprouting immediately and overnight the liquid turns rock-solid. Sort of like a geode.

  68. Debra Thomson says:

    Really sorry, but is is me, Stephanie, again. I am just curious as to whether sugar will grow crystals faster than salt, or vice-versa? (I think I should try this and experiment with it…) THANK YOU!

  69. Debra Thomson says:

    Also, why does it make a variable whether you use a glass or plastic container? How do the results change? Thanks!

  70. Debra Thomson says:

    What would be the problem with having too much sugar in the solution? Just curious.
    -Stephanie 13 yrs. old

  71. Sounds like you have too much water in your solution. These solutions needs to be prepared very carefully, and it will take time to fiddle with the right sugar-to-water ratio. Dump your solution in a pot, warm it up and add more sugar… until you can’t dissolve any more into the liquid. Let it cool and stick it back int he jar and wait impatiently for a few days… 🙂

  72. sevy keble says:

    We did everything as the video said and the crystals have been standing for about a week and no one has been touching them, but they aren’t growing?!
    Why?
    sevy keble

  73. Hi Andrew & Lois,

    It sounds like you had too much sugar in your solution if you saw crystals that fast. Just add a bit of water, stir, wait, and watch. If you still see crystals zooming out of the solution, you need more water. Most kids see teensy crystals in about a day or so. Does this help?

  74. Andrew McClintick says:

    Dear Aurora,
    I do not think we did the rock candy crystals right. But we still saw crystals about 20 minutes later. Do you now why?
    Lois 8