Alum Update

While we're waiting for the lemon battery do-over (and possibly other redox experiments), I thought I'd take another look at what the alum crystals are doing.

John had to stop growing the clear crystal when the string broke before Christmas. Anthony is still growing his green crystal, but it's getting ... kind of mushy. I think it has to do with the new solution we put it in.

We tried to make more "alum juice" by taking all the grains of alum we saved after siphoning off the liquid from time to time. Anthony warmed the juice in the microwave so that the alum would dissolve, but I think he let it get too hot. We left the cup of juice to cool to room temperature and went out for the day. (If we had put the big crystal back in the juice when it was still warm, it would have dissolved, because the warmer liquid could take more alum into solution.)

When we got back we found the big chunks of alum you see here. They're sort of deformed, I believe because they formed too fast for the crystal structure to develop nicely. It's interesting that they kept the green food coloring as well, which the slower growing crystals didn't (once they had dried). We may dissolve them and try again.

Still growing

The alum crystals are slowly getting bigger. But a lot of the alum in solution in the cups crystalizes out into separate tiny little crystals. Whenever there are too many little crystals in the cup, we decant the solution into a clean cup. And I put the little crystals into a third cup I started.

At first nothing grew. I figured there wasn't enough alum in the solution. But little by little I added more crystals and let the water in the cup evaporate.

Then the other day, I glanced in the cup and saw these, lying on the bottom:

Without the food coloring, they look like diamonds waiting to be put in rings. So cool! All the crystals are flat on the bottom, though. I tied one on a string to see if it would grow, and if it would even out on the flat side. Updates in a few days.

Big Alum Crystal Update

After a gravelly start, our alum crystals are growing nicely.

Just leaving the solutions sitting in clean cups for a couple days before we could get back to them allowed some good-sized seed crystals to grow. Each kid picked one and tied it to a string. By day two you could see the crystal bulging around the string, and by today, day three, the crystal had swallowed the string and kept growing around it.

Because the boys put food coloring in their water, the strings can be seen clearly. (The string picked up more of the coloring than the crystal, which shows just the slightest tinge of color.)

Oh, I did end up saving the tiny crystal grains, re-melting them in hot water, and putting a leftover seed crystal into a third cup to see if I could get it growing. But I think I put too much water in for the amount of alum, because the seed just disappeared in the solution. I keep adding more alum as the kids clean out the little grains from the cups (by decanting the solution into a clean cup). Eventually, I figure, it should evaporate enough to become saturated and start to form crystals.

Crystal Update

The salt crystal gardens continued growing, without any additional ingredients for several days. Eventually, they began to wilt a little.
Here again is the progression:

Which stage do you think is the best?

As for the big alum crystal...

our seed crystals came out SO small that we couldn't work with them.

So we're going to try melting them down (just that little spice container was three bucks)

and start over. I found, and then lost, a link to tips for growing better crystals.

When I find it again I'll add it here.

What is alum used for?

Long-Haired Hare

We're trying another crystal project from About.com, growing giant crystals of alum. Alum -- or hydrated aluminum potassium sulfate, KAl(SO₄)₂^.12H₂O -- is sold in outrageously expensive little containers with the spices. It's used to make pickles crispy.

The kids wanted to know more, so we looked it up on Wikipedia.

You'll find alum in styptic pencils to staunch the bleeding from shaving, and underarm deodorant, because of both its antibacterial and anti-wetness properties.

Oh, and it's an astringent, which is why they can use it in Looney Toons cartoons to shrink heads. And you thought the only thing kids learned from watching Bugs Bunny was classical music!

It's Alive!

By this morning Anthony's crystal garden was trying to climb out of the bowl.
As the day progressed, the turquoise food coloring stopped spreading,
and the bulbous projections sprouted white tips.

John's garden sprouted nicely overnight as well.
Tonight it looks like a bunch of miniature multicolored Afro wigs.

How does your crystal garden grow?

Very well, thank you!

We changed the ingredients...
Mixed them together BEFORE pouring them over our sponge bases...
And in just a few minutes...

Crystals!
Anthony used double the amount of bluing, so his salt solution is more dilute.
(You can see a crystal formation climbing up the side of the bowl.)

John put some dots of food coloring on his.
(Note that the red spots grew the least.)
(I am very happy.)

Crystal Garden continued

Day 2 Day 4

Our damp blue piles of salt are not as garden-like as I hoped. I knew there were different versions of this project, but I wanted to try the easiest first. Now that we have proved it's not so simple (at least not for us), I've done some searching and found some areas to fiddle with:

• We can use distilled water instead of tap water.
• We can use un-iodized salt.
• We can add ammonia to the mix.
• We can combine the ingredients first, letting the salt dissolve in the liquid, before pouring over the base.
• We can use less stuff or a bigger base.

Barring major snowstorm, we will try to get ahold of some distilled water, un-iodized salt, and some aluminum pie pans and give this another go on Monday. Maybe I'll also pick up one of these:

Amazing Christmas Tree

Crystal Garden Day 1 (if we're lucky)

My next Hands-On Learning column for Home Education Magazine will be a crystal-growing project, and there are several versions I want to try. The one we started today comes from The Joy of Chemistry and uses Mrs. Stewart's Bluing. (You can also find the directions, an explanation -- and anything else you ever wanted to know about this old-fashioned, non-toxic laundry product -- on their website.)

We combined aspects of both sets of directions. Per JoC, we used an ordinary kitchen sponge, cut into cubes, as the base. But we left out the ammonia they recommend to see if it would work without, since MSB's website said it was helpful but not necessary. The sponge bits were sprinkled with water, salt and bluing.

As you can see, it really is BLUE. Prussian Blue, to be exact. According to Wikipedia, the chemical formula of PB is Fe₇(CN)₁₈(H₂O)_x where 14 ≤ x ≤ 16.

The PB is insoluble. The Mrs. Stewart's liquid is not a solution, but a colloidal suspension in which very tiny particles of the dye are floating. These small crystallites serve as seeds for the salt crystals that (hopefully) will be growing over the next few days.

Hah! I love it when I sound like I know what I'm talking about!