Renthead Mommy Posted March 5, 2010 Share Posted March 5, 2010 As part of our crystal study, we were trying to make rock candy to see the crystal shape. Two tries and five cups of sugar later, I still don't think it's right. I used a candy thermometer. First batch hit 260 degrees like the directions said. The directions also said let it cool to closer to room temperature before pouring in the jar. It seemed to crystalize right away and before it was even close to room temperature. After scraping out that batch, we tried again. This time I looked it up in my cookbook and it said heat to 247-255 degrees. So we tried again. This time it was clear and and would make ribbons when I pulled a spoon out of it. I didn't let it cool as much, poured it into a glass jar. But it's just one solid clump at the bottom of the jar. Did I do the second batch wrong also? I thought I would be able to see through it and watch the crystals attach to the stick. Is it going to do something or in two weeks am I just going to be throwing out a jar with a stick glued into the bottom of it? Quote Link to comment Share on other sites More sharing options...
Renthead Mommy Posted March 5, 2010 Author Share Posted March 5, 2010 bump Quote Link to comment Share on other sites More sharing options...
GoVanGogh Posted March 5, 2010 Share Posted March 5, 2010 We made rock candy last year. Had to start it three times before we got it figured out. But I can't remember now what we were doing wrong. I do know we tried several different recipes. The last one had more sugar in it and cooked to a higher temp. Since I can't be of more assistance, I'll at least :lurk5: for you. Quote Link to comment Share on other sites More sharing options...
Hen Posted March 5, 2010 Share Posted March 5, 2010 we were supposed to do this project last week, but I heard people were having trouble with it, so I did it with borax soap instead, and it came out great..it was super easy. I then went and bought the candy to hand out. I just did a post on the project on my blog, with directions, Growing borax crystals, a homeschool project Quote Link to comment Share on other sites More sharing options...
JillZ Posted March 5, 2010 Share Posted March 5, 2010 The Exploratorium has a few tips on how to make rock candy. http://www.exploratorium.edu/cooking/candy/recipe-rockcandy.html# As a chemist, I would say to make sure all of the sugar dissolves completely before taking it off the heat (ignoring the temperature). Also, if you cool it down too quickly, the crystals may start to "crash out" of the solution before you're ready for them to. I've never made rock candy before, but it sounds like fun! (Full disclaimer: I'm actually a theoretical/computational chemist, so I don't really do crystallizations in real life, but I did a lot in undergrad!) Quote Link to comment Share on other sites More sharing options...
SonshineLearner Posted March 5, 2010 Share Posted March 5, 2010 It's all over our Classical Conversations Directors board how hard it is to do rock candy. We just did them a couple of weeks ago... I chose to do salt crystals.... they didn't work either. (Even though they worked at home...) Quote Link to comment Share on other sites More sharing options...
fishmummy Posted March 5, 2010 Share Posted March 5, 2010 After five students who each had this as an assignement over the years...I never had any success. I always wondered if it was akin to having bread dough rise or making divinity candy and our humidity levels just did not cooperate. We did have tremendous success with Borax...and althought you cannot eat the fruits of your labor, you can see the process and your children will be excited. wendy Quote Link to comment Share on other sites More sharing options...
Renthead Mommy Posted March 5, 2010 Author Share Posted March 5, 2010 Thanks everyone. I've got borax downstairs, I'm going to try that. I hate the thought wasting more sugar. And as for the eating, well, I doubt he'd eat it anyway, and his father (the dentist) will probably be happier anyway (less about the sugar - more of an issue with the chewing on hard stuff). I'm sure it's some sort of temperature issue. But who knows. In theory, it shouldn't be this hard. I mean it's one step past 'boil water'! LOL! But man, you've got to it right on the head with that one! LOL! Off to try the borax crystals! Thanks! Quote Link to comment Share on other sites More sharing options...
Carol in Cal. Posted March 5, 2010 Share Posted March 5, 2010 The crystals formed (they can't help it. It's a saturated solution, so when it cools or the water starts to evaporate, the sugar can't all stay dissolved.) on the bottom of the measuring cup, rather than on the cord. It was really, really annoying. Plus it was difficult to get them out, once formed. Quote Link to comment Share on other sites More sharing options...
fishmummy Posted March 5, 2010 Share Posted March 5, 2010 Good Luck with your Borax Crystals!!! Wendy Quote Link to comment Share on other sites More sharing options...
Dmmetler Posted March 5, 2010 Share Posted March 5, 2010 According to my Chemistry professor father, that happens when the solution has is supersaturated, so the crystals form on each other instead of on the string and just fall out. It's a really fine balance between a solution that takes forever to evaporate and crystalize, and one that's supersaturated. I agree that borax crystals work better. Quote Link to comment Share on other sites More sharing options...
Mom-ninja. Posted March 5, 2010 Share Posted March 5, 2010 I've never had it work Quote Link to comment Share on other sites More sharing options...
Aubrey Posted March 5, 2010 Share Posted March 5, 2010 The Exploratorium has a few tips on how to make rock candy.http://www.exploratorium.edu/cooking/candy/recipe-rockcandy.html# As a chemist, I would say to make sure all of the sugar dissolves completely before taking it off the heat (ignoring the temperature). Also, if you cool it down too quickly, the crystals may start to "crash out" of the solution before you're ready for them to. I've never made rock candy before, but it sounds like fun! (Full disclaimer: I'm actually a theoretical/computational chemist, so I don't really do crystallizations in real life, but I did a lot in undergrad!) We just did this this morning, & this is basically the thinking behind ours. A couple of differences from what our instructions said vs what I've read here: 1. Crystals will take 7-10 days to form. 2. Crystals will form on the top of the water, attached to the string, & on the bottom of the jar. 3. Put a bag over the top of the jar to slow the rate of evaporation. That said, we just finished *starting* ours less than an hr ago. *Crossing my fingers!* Oh, & we did the borax around snowflake-shaped pipecleaners at Christmas a couple of mos ago. They were BEAUTIFUL! Quote Link to comment Share on other sites More sharing options...
stormy weather Posted March 5, 2010 Share Posted March 5, 2010 (you know Alton Brown)on fudge making that could explain why you ended up without crystals. Apparently you have to stir vigorously at the right point in time to get the crystals to even begin to form. I found a sort of transcript of the program here. HTH. Looking at that makes me want to watch them all over again and use them for some sort of science curriculum. It also makes me want fudge. Quote Link to comment Share on other sites More sharing options...
Renthead Mommy Posted March 5, 2010 Author Share Posted March 5, 2010 That said, we just finished *starting* ours less than an hr ago. *Crossing my fingers!* If at this point you have something more than a large crystal chunk of sugar in your jar, you are ahead of us! Reading all these has helped me figure out some of what went wrong. The first one I think heated up too high, but then too much of the water evaporated out. It completely crystalized while still hot in the pan. I have a Classico spagetti sauce jar filled with harden sugar. Some of it looks crystal like, most of it looks like a big hunk of sugar. Exact same amount of everything in second back and I've got 2 1/2 inches of sugar glass. But it's not see through. It looks like the top of the honey jar once it's started to crystalize. The wooden skewer is stuck in there and NEVER coming out! Somebody said something about theirs being stuck in their measuring cup - I had a feeling something like that would happen, that was why I saved up the spagetti sauce jars! We'll see what happens with the borax. As for the rock candy - well, I promised my 7yo we'd get some so we could see the sugar. Even if he doesn't get to eat the rock candy, he'll still make out I'm sure! We have to go to the choclatier's to the rock candy! I know he'll con me out of something in there! LOL! Quote Link to comment Share on other sites More sharing options...
Cinder Posted March 6, 2010 Share Posted March 6, 2010 A couple of differences from what our instructions said vs what I've read here: 1. Crystals will take 7-10 days to form. 2. Crystals will form on the top of the water, attached to the string, & on the bottom of the jar. 3. Put a bag over the top of the jar to slow the rate of evaporation. Yes, this. It took at least a week to get crystals. They were at the top, on the string, and at the bottom. We covered the jar with plastic and set it in a place where it wouldn't be disturbed. Sudden jarring is bad--it sets the crystals, thus ruining your experiment. As to attaching the string, we used cotton, moistened it, then rolled it in some dry sugar before placing it in the jar of sugar water. We also tied it to a pencil, which we set over the opening of the jar. Oh and cut the string so it's not long enough to touch the bottom of the jar. HTH, Cinder Quote Link to comment Share on other sites More sharing options...
OrganicAnn Posted March 6, 2010 Share Posted March 6, 2010 First saturate the string in a little sugar water and let dry. This will make the crystal grow on the string better. It does take several days to form the crystals. Put a bag over the top of the glass or jar (especially if you have any little flies around - yuck). You can take a spoon and break the crystals that form at the top and do it several times. After you think the crystals are big enough. Take them out and allow them to dry for a day. Quote Link to comment Share on other sites More sharing options...
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