Name: Alicat8
Original Inspiration: http://offbeatfamilies.com/2011/06/rainbow-themed-baby-shower
What I Did: This was for my rainbow themed baby shower. I insisted on making my own cake, because I thought this was so cute. It seemed easy. Well I spent a few hours the night before baking all the cakes, then 15 minutes before the shower decided to start stacking them. I got to about the 3rd layer before they collapsed and fell into a mess. Luckily my husband ran out and bought a cake. This one ended up being served out of a huge bowl.
My Result:
Next Time I Will: Next time I would level off the layers. The rounded tops made the stacking impossible.

Oh my gosh! I tried a rainbow cake too - what a disaster! I tried the “cook it in a jar” style SEVERAL times! I tried it in the oven, in the microwave, in the oven with less cake mix - they were all unmitigated disasters. I finally made it in a pyrex bowl and made a sunshine cake!
I have made a 3 level cake a few times and they trun out just fine. Maybe add more icing to make sure they are level before you add another row of cake.
This kind of cake disaster happened once, just minutes before my daughter’s birthday party (and there was no time to run out to the store and get another) — so I dumped the cake, frosting, and sprinkles into a big mixing bowl — stirred it all up and called it “Birthday Stew”! We served it up with ice cream and it was a gigantic hit with the kids. So we made birthday stew a family tradition after that!
Did you freeze the cake layers overnight before assembling the cake?
i didn’t freeze them-i should have, and i did think of it as they were falling. when i did it, i swear i was at the height of pregnancy brain and party planning stress.
we basically had shower cake stew too-it was still pretty and delicious.

Try using 3 to 4 wooden craft dowels cut to height of each layer, and place smaller than cake diameter card board round to create a sturdy structure. Not really wise to just stack layers of cake with no foundation.
You might want to invest in an oven thermometer (~$10) to be sure you’re getting the temperature right.
http://media-cache-ak1.pinimg.com/192x/44/b1/d1/44b1d12031d0a27f0f929b7b41c2334e.jpg
Even if you pre-heated the oven properly, sometimes the oven’s gauges are just incorrect. I have to add about 25 degrees F with my oven. A quick visual sort of on topic - temp makes a big difference:
http://www.chef-in-training.com/blog/wp-content/uploads/2012/05/cooking+insight+cupcake1.jpg