Thread: Anyone make Crystals? I need help.

I try to have a project for my Grandkids and I to do frequently. The latest choice was making crystals for fun and would also be educational regarding molecules. I bought a five pound tub of Alum and 5 large flat bottom, glass globes.

The sites I found online sounded very easy. Well, I have used about 3 cups of the Alum and have been unsuccessful with each attempt. Nothing forms on the glass after two days. The 'Seed' crystals form on dental floss but when added to a new batch to 'grow' - - they just dissolve. The water is supersaturated with alum and will hold no more. What am I doing wrong?
Sue

I can see this ending badly.

One of the grandkids is going to brag about their newfound knowledge of chemistry at school one day and casually remark, "My grandma showed me how she makes 'crystal' in her basement!" as a teacher walks by.

Then protective services will be alerted and the DEA will storm your house looking for meth.


*Ahem*


Just kidding?

Try using distilled water, by the way.

Try filling the jar with the ultra saturated water, then weight the end of the floss and drop it in so that it's about halfway down. Wait 24+ hours, and it should be good.

EDIT: Have you been told to use the floss? The wax on the floss could be inhibitive, but that's just a guess.

Originally Posted by Sue

The 'Seed' crystals form on dental floss but when added to a new batch to 'grow' - - they just dissolve. The water is supersaturated with alum and will hold no more.

If the crystals dissolve instead of grow that means that the solution is not saturated, or at least not saturated at the vicinity of the crystals. The same thing with no precipitations at the bottom altogether.
One thing I can think off the top of my head is that the water may warmed up since you dissolved the alum, and even if it was a saturated solution at the lower temperature it isn't going to be at the higher one.

Try heating the water to almost boiling.It will dissolve more chemicals that way and they should precipitate out better. If you could slowly cool the solution it should be even better. Even better use sugar and then you can eat the results.

Originally Posted by thebigspendur

Try heating the water to almost boiling.It will dissolve more chemicals that way and they should precipitate out better. If you could slowly cool the solution it should be even better. Even better use sugar and then you can eat the results.

Now that's an idea!
The kids would just not like that!! ........( load them up on sugar and send them home).

I make a living growing crystals. What salt is your alum, this can make a difference as alum refers to a number of chemical compounds. Normally people call aluminum ammonium sulfate alum but that is not always the case. You may want to chose a salt that increases solubility at high temperature, NaCl would not be the best. If you do that, supersaturation, already mentioned, would work for you. Having a thread that promotes nucleation of the crystals would increase your success as well. I remember growing stalactites using 2 jars filled with salty water and a piece of yarn connecting them. Distilled water would not help in most cases, on the contrary, it would make it harder. This page would provide some of the fundamentals:

Grow Crystals - Crystal Growing Projects Recipes and Information

I have an idea for you, why not try to make rock candy? This way, you can eat the end product.

Science of Candy: Rock Candy Recipe

If you have questions about the chemistry etc, please do not hesitate to ask. As for the alum, i will take some if you want to get rid of it.

Al raz.

Yeah, make rock candy- it's so tasty!

Al raz, how do you make a living growing crystals? If someone around here said they were growing crystals, I'd probably call the cops

Go ahead, make my day ;-). I thought this quote would be funny in this context. There is nothing exciting about growing the crystals I grow, plus I do not grow them at home. I think they would be pretty disappointed. ;-)

Al raz.