[balaruman]

Complete chemistry noob here, but really curious about the stuff that inadvertently grown in my fridge.

It started when somebody gave me some advice on how to get rid of unpleasant smells in the refrigerator - a friend suggested some baking soda (sodium bicarbonate). I wasn't paying too much attention at the time, so I got it wrong - instead of dry baking soda I used baking powder dissolved in a glass of water. Then I put it in the fridge and forgot about it for ~4 weeks.
When I found it again, my glass looked really interesting : there were large (~3cm long, 5mm wide) transparent crystals grown along the inner side of the glass. There was other stuff too : fine white powder at the bottom (probably starch), needle-like transparent crystals in the water, and white small crystals along the rim of the glass.

So, what happened there ?

I did some research and by the looks of it the large crystals are sodium acetate. However, the powder I used was supposed to contain sodium bicarbonate and some acid (phosphate acid?) in the exact proportion required to react - so how could it also react with the traces of acetic acid in the fridge to produce the crystals ?
Again, I'm a complete noob, so maybe I got it wrong.

Is there any (simple) way to test using only stuff already present in my kitchen ? And to optimize growth (bigger, clearer crystals).

Thank you.
(see attached photo of the crystals)

[Arkcon]

The label on the can of baking powder will let you know the chemicals  -- mine has sodium bicarbonate , sodium aluminum sulfate and calcium phosphate.  They all react to make mixed salts, and even if separate, the initially pure crystals may have grown together into each other in a small container.  Growing them slowly in the cold is a great way to get large crystals, which is nice.  I doubt your refrigerator is so saturated with acetic acid vaporizing from jars of other stuff that it grew noticeable crystals in the mix.

[balaruman]

Thanks for the reply !

The baking powder I used contains : sodium bicarbonate, disodium diphosphate, corn starch.

New development : after a few days the crystals are no longer shiny and transparent, they turned dull white and crumbly. In fact, they look and feel like chalk now 

I'm going to repeat the experiment, using 2 glasses - one with the original baking powder and the other with pure sodium bicarbonate.

[Borek]

they turned dull white and crumbly. In fact, they look and feel like chalk now 

That probably suggest high water content (http://en.wikipedia.org/wiki/Hydrates#Inorganic_chemistry). Once you took them out of water they started to dry.

[billnotgatez]

I know that this is an old post but I am adding some information that may be of interest should someone doing a search.
The way typical refrigerators work is not necessarily just holding a constant temperature.
This link may be of interest

http://www.ehow.com/how-does_4699952_frostfree-freezer-work.html