Troubleshooting Rock Candy
February 16, 2023 7:44 AM Subscribe
I tried to make rock candy with my kiddo. It's failed twice. Can you help me fix it?
Right now, I have 3 cups of almost solid sugar/water mixture and 1 that appears to be 'correct' - in that crystals seem to be forming and the solution is a syrup consistency. What's going on with these solid mixtures? They're almost like fudge without the cream and butter. I'm thinking I had the solution at a high temperature for too long. Either than, or I oversaturated the solution.
First failure: After 6 days, only about a couple of milimeteres of sugar crystal formed on the bamboo sticks I had pre-coated in sugar. My ratio of sugar to water was about 2.25:1.
Second failure: I decided that I hadn't saturated the solutions enough. So I poured the sugar solution from each cup back into a pot (I did this one by one because they are all different colours), added another cup of sugar to each solution, brought it to a boil, let it cool for about 15 min, poured it back into the cup and put the bamboo sticks (the ones that had a couple of mm of crystal formation in them) back in.
Can I fix this? I don't want to have a super disappointed four-year-old, but I also don't want to start over and waste 12 or more cups of sugar.
Right now, I have 3 cups of almost solid sugar/water mixture and 1 that appears to be 'correct' - in that crystals seem to be forming and the solution is a syrup consistency. What's going on with these solid mixtures? They're almost like fudge without the cream and butter. I'm thinking I had the solution at a high temperature for too long. Either than, or I oversaturated the solution.
First failure: After 6 days, only about a couple of milimeteres of sugar crystal formed on the bamboo sticks I had pre-coated in sugar. My ratio of sugar to water was about 2.25:1.
Second failure: I decided that I hadn't saturated the solutions enough. So I poured the sugar solution from each cup back into a pot (I did this one by one because they are all different colours), added another cup of sugar to each solution, brought it to a boil, let it cool for about 15 min, poured it back into the cup and put the bamboo sticks (the ones that had a couple of mm of crystal formation in them) back in.
Can I fix this? I don't want to have a super disappointed four-year-old, but I also don't want to start over and waste 12 or more cups of sugar.
Response by poster: The bamboo sticks are held in a clothespin about 1 inch from the bottom of the cup.
posted by kitcat at 8:24 AM on February 16, 2023
posted by kitcat at 8:24 AM on February 16, 2023
Check your sugar for anti caking agents, which might interfere with recrystallization.
posted by jamjam at 8:48 AM on February 16, 2023
posted by jamjam at 8:48 AM on February 16, 2023
Best answer: So what the idea is when making rock candy this way, is that you're trying to do is make a solution of sugar in water that's 100% saturated at room temperature, let it sit and evaporate so that the sugar would have been dissolved by that evaporated water precipitates out, and make sure the only place it has to precipitate out is on the sugar coated stick you stick into it, forming nice big crystals.
It sounds like your first "failure" was doing this! You did get some crystals growing. If your sugar solution wasn't pretty much 100% saturated, nothing would have formed at all.
They just weren't growing fast enough.
So my guess would be that the problem was the water wasn't evaporating fast enough.
I did see some recipes suggest covering the solution with plastic wrap - this seemed wrong to me. It would be hard for evaporating water to go anywhere and would probably make evaporation really slow. Another recipe suggested covering things with wax paper instead. This seems more sensible since it would allow water vapor through more easily while still protecting the mixture from bus and dust.
Of course if you weren't covering it at all then clearly I'm barking up the wrong tree here.
And yes, the second failure, if you took an already saturated sugar solution and tried to add more sugar, then you probably just got a sludge of sugar crystals and water or a supersaturated solution. If your mixture was at all not perfectly transparent, that means there's microscopic sugar crystals deflecting the light, and any sugar that precipitates out is just going to stick to those and make them bigger and make the liquid sludgier until it's basically fudge. Which is what you mostly got.
I think with the one that worked, my guess is that the mixture wasn't perfectly mixed, so sugar crystally sludge was mostly sunk to the bottom with a layer of just sugar/water solution on top, so the first cup you poured was just slightly supersaturated sugar/water mixture and was OK, while the rest of them has enough undissolved sugar to sludge-ify things.
posted by Zalzidrax at 9:51 AM on February 16, 2023
It sounds like your first "failure" was doing this! You did get some crystals growing. If your sugar solution wasn't pretty much 100% saturated, nothing would have formed at all.
They just weren't growing fast enough.
So my guess would be that the problem was the water wasn't evaporating fast enough.
I did see some recipes suggest covering the solution with plastic wrap - this seemed wrong to me. It would be hard for evaporating water to go anywhere and would probably make evaporation really slow. Another recipe suggested covering things with wax paper instead. This seems more sensible since it would allow water vapor through more easily while still protecting the mixture from bus and dust.
Of course if you weren't covering it at all then clearly I'm barking up the wrong tree here.
And yes, the second failure, if you took an already saturated sugar solution and tried to add more sugar, then you probably just got a sludge of sugar crystals and water or a supersaturated solution. If your mixture was at all not perfectly transparent, that means there's microscopic sugar crystals deflecting the light, and any sugar that precipitates out is just going to stick to those and make them bigger and make the liquid sludgier until it's basically fudge. Which is what you mostly got.
I think with the one that worked, my guess is that the mixture wasn't perfectly mixed, so sugar crystally sludge was mostly sunk to the bottom with a layer of just sugar/water solution on top, so the first cup you poured was just slightly supersaturated sugar/water mixture and was OK, while the rest of them has enough undissolved sugar to sludge-ify things.
posted by Zalzidrax at 9:51 AM on February 16, 2023
Response by poster: Zalzidrax I think you're right! I read something that suggested straining the sugar solution with a coffee filter, on my second try to get rid of any stray crystals, but it didn't explain why. I just thought - well, that's way too much work.
So I think I can try boiling the three bad ones again, adding a little bit more water and making sure (as best as I can) that there are no stray crystals in the solution. Does that sound right?
posted by kitcat at 12:03 PM on February 16, 2023
So I think I can try boiling the three bad ones again, adding a little bit more water and making sure (as best as I can) that there are no stray crystals in the solution. Does that sound right?
posted by kitcat at 12:03 PM on February 16, 2023
So, I don't know anything about making rock candy, but what jumps out at me is that you seem really committed to re-using the sugar and water from your failures. Is there a reason you aren't just making a whole new batch?
posted by QuakerMel at 8:32 AM on February 17, 2023 [2 favorites]
posted by QuakerMel at 8:32 AM on February 17, 2023 [2 favorites]
This thread is closed to new comments.
How are you suspending the bamboo into the cups?
posted by EmpressCallipygos at 8:00 AM on February 16, 2023 [1 favorite]