Not Martha

experiments in Rainbow Cakes

the original rainbow cake

This past St. Patrick’s Day I made a Leprechaun Trap Cake, shown above, which revealed a nice rainbow shape inside each slice. I created the rainbow by pouring colored cake batter into an angel food cake pan one color on top of the other and it came out surprisingly well. (More details on the amounts of colored batter I used are in the original post.) At the time I wondered if doubling the recipe or using different cake pans would result in the same effect and I’ve made a half dozen cakes over the past month to find out. The results are below and it turns out the answer is “nope”.

For each of the following cakes I used the same boxed white cake mix, the same gel food colorings and the same technique to layer the batter.

cross section of a rainbow cake

Two boxes of cake mix in an angel food cake pan. For my original cake I used one box of cake mix in this same angel food cake pan. Doubling the amount makes a big difference and the cake almost spilled over the top of the pan while baking. If I’d leveled this one I would have had a swoopy and uneven rainbow, but it would have been there.

cross section of a rainbow cake

Half a box of cake mix in a 6 inch round cake pan. This was my most successful test variation. The cake shown has been leveled and turned out onto a plate, each slice had half a rainbow.

cross section of a rainbow cake

One box of cake mix in a 6 inch round cake pan. I was hoping that the flat bottom of the cake pan with lots of batter would result in a tall rainbow, but instead I got something that looks more like a volcano. I didn’t level this cake.

cross section of a rainbow cake

Half a box of cake mix in a 4.5 x 8.5 inch loaf pan. I hoped the flat bottom of a loaf pan would give me similar results to the bundt pan but the batter didn’t quite behave the same way. I leveled this cake before cutting into it and didn’t realize that the leveled top held all the blue and purple colors, so I put it back on for the sake of the picture.

cross section of a rainbow cake

One box of cake mix in a 4.5 x 8.5 inch loaf pan. Another loaf pan experiment this time with twice the batter, and another volcano like result.

cross section of a rainbow cake

Two boxes of cake mix in a round mixing bowl. Here again I was hoping a tall cake would result in a nice tall rainbow. I didn’t get that but I did get some very impressive swirling down the center of the cake and back up around the sides of the bowl. The center of this cake never quite baked. A failure all around but it’s pretty cool to see how the batter moves while it’s baking.

My conclusion is that using less batter in a flat bottomed pan will more likely result in the rainbow arch I was hoping for. And that I got very, very lucky for the first version of this cake that I made to come out so nicely. Call it the luck of the Irish?

· comments [42] · 04-11-2011 · categories:food ·

42 responses so far ↓

  • 1 M // Apr 11, 2011 at 9:20 am

    Thanks for posting the experiment results – this is fascinating!

    I’m wondering what would happen if you baked one in a water bath or with cake magic strips – whether that might reduce the volcano-ing? (of course, it might cause other problems!)

    With wedding cakes, one uses those even-bake strips (or a lower oven temp, or strips of wet toweling, and water baths for cheesecakes) to help the cake bake more evenly, rather than baking outside-to-inside (which, I think, might be the force expanding the batter on the edges of the pan and squashing the unbaked batter on the center parts up the volcano spout). In regular cakes, this reduces doming, cracking, and unbaked-center-overdone-crust-syndrome, and it might also result in a less-disturbed cake rainbow?

    Also, I’m glad you were lucky! :-) I would also note that you were very clever, not just lucky – the choice of the cake pan was lucky, but the rest was you being very smart about how to make rainbow cakes turn out beautifully!

  • 2 Meridith // Apr 11, 2011 at 9:36 am

    I am wondering how much gel coloring you used for each color. I am making a rainbow cake next week for my 5 year old and I’ve seen some cakes where the colors look washed out. Yours came out so beautifully vibrant! Thanks!

  • 3 megan // Apr 11, 2011 at 9:59 am

    M – I did think about all the fancy baking gadgets and water baths and, you got it right, decided it was a whole different level of complicated that I didn’t really want to get in to. I am curious how it would effect how the batter moves around though. I did bake all my cakes at 350 when I knew they would dome less if baked at a lower temperature, but I was being stubborn about using the same conditions as the initial cake (those being, the box directions). And thank you!

    Meridith – My only answer is that I eyed it. I divided the batter into small bowls and added food coloring until the batter was as bright as I could get it. It does turn your tongue funny colors! Especially if you color the frosting as intensely as I did in the first rainbow cake — I actually suggest less food coloring in the frosting if you can. I also admit that all the food coloring was sort of ridiculous!

  • 4 Kelly // Apr 11, 2011 at 12:30 pm

    WoW! Thanks for the scientific analysis!! Will definitely give your original a try. YOu’ve saved us all so much work.

  • 5 Katharina // Apr 11, 2011 at 12:32 pm

    I wonder if using glass instead of metal loaf pans changed up another significant variable in your experiment…your initial cake was baked in a metal pan, no? Just a thought.

  • 6 Seanna Lea // Apr 11, 2011 at 12:46 pm

    While these didn’t produce the rainbow effect you were looking for, they are still awesome looking (well, some of them). I especially like the 1 box of cake mix in the loaf pan. It is a lovely volcano!

  • 7 Meridith // Apr 11, 2011 at 12:47 pm

    Thanks, Megan. I think I might just stick with white frosting and rainbow non pareils. I can’t wait to try it. Thanks for the inspiration!

  • 8 megan // Apr 11, 2011 at 12:50 pm

    Katharina – I considered that but at this point I cannot bring myself to bake one more rainbow cake, at least not until next year.

  • 9 Ev // Apr 11, 2011 at 1:54 pm

    Megan, I just wanna know what you DID with all of that cake??!! Are all the songbirds in your neighborhood pooping rainbows?

  • 10 megan // Apr 11, 2011 at 2:24 pm

    Ev – Sadly we had a slice of each and tossed the rest. Since I needed to get a photo of the cross section I didn’t think giving an already cut into cake away seemed all that appealing!

  • 11 Leah Z // Apr 11, 2011 at 3:44 pm

    We were so inspired by the rainbow cake you made for St. Patrick’s Day, my sister and I decided to make a rainbow-ish cake for her birthday. We used a double recipe of white cake and a basic butter cream frosting (with about 1/2 a cup of cream cheese added to cut the sweetness) and gel food coloring to get just the right hues of pink and purple that Amy wanted. We were so excited with the outcome we didn’t even mind that the cake was far more beautiful than it was delicious. Thanks for the inspiration! check out our cake:

  • 12 Nina // Apr 11, 2011 at 6:07 pm

    This is empirical research at its best.

  • 13 Hypothetical Woman // Apr 12, 2011 at 2:35 pm

    Wow, that’s quite a colourful experiment! That last one was fascinating, it’s a pity it didn’t bake all the way through but it’s interesting to see how the heat moves through the cake during baking.
    I think the cake batter I generally use is a bit thicker than this; I wonder what sort of results I’d get? Hm, you’ve got me thinking now…

  • 14 Nat@ dear little house // Apr 12, 2011 at 10:43 pm

    What a marvelous experiment! Thanks for sharing :)

  • 15 Therese // Apr 12, 2011 at 11:35 pm

    This post is fantastic! Thanks for a colorful start to my day!! I need to get a hold of some food coloring ;-)

  • 16 Loretta // Apr 17, 2011 at 9:03 pm

    I made a rainbow cake for my sons 1st birthday. )I used the angel food pan.) It was a SMASH! I found, though, that if you don’t mix the cake batter enough it won’t rise properly and you won’t get the rainbow. It was a good thing I tried the cake before the birthday!

  • 17 hikerlola // Apr 25, 2011 at 1:22 pm

    Mine wasn’t quite as fabulous as yours, but sooo much fun! All of my coworkers were seriously impressed. Thanks for the inspiration!

  • 18 Wishful thinking « Five Things // May 11, 2011 at 8:45 pm

    […] 1. another rainbow cake […]

  • 19 Meister @ The Nervous Cook // Aug 7, 2011 at 4:49 pm

    I’m sort of charmed by these “failed” rainbows, and would probably be delighted if any one of them wound up on my table! Call me easy to please…

    (Good thing I’m not a Leprechaun, I guess; I’d be wicked easy to trap.)

  • 20 Lana // Oct 9, 2011 at 6:04 am

    Love this! Just tried it for my daughter’s birthday! It was a hit!

  • 21 Nejla // Oct 11, 2011 at 8:55 am

    Hi Martha,

    I`m a big big big bigg! fan of you from Turkey.. Since I saw your rainbow cake I knew I must make it!! I couldn`t even sleep of thinking about it.. It was just sooo amazing… First I made it with a round bottomed pan and it was very different.. check it out Then I finally found a flat bottomed pan at IKEA and finally I made it!!! Thanx for the inspiration!!!!. Here is my cloudy rainbow cake on my Turkish blog!!!.

  • 22 Shantel // Feb 12, 2012 at 3:06 pm

    I’m just wondering if you tried a bundt pan. I didn’t see it in your list of tries.

  • 23 megan // Feb 12, 2012 at 5:38 pm

    Shantel – I didn’t try it in a bundt pan so I’m afraid I cannot say how the effect would work out.

  • 24 Amanda Meehan // Mar 7, 2012 at 7:07 pm

    Hi Megan,

    What size was your angel food cake pan?

    I am entering in a silly bake-off and I think I can pull this off, but in order to not mess with what you’ve tried, I ordered an angel food cake pan since all I have is a bundt cake pan.

    I got my pan today and it’s much smaller than I expected 8 x 3 3/4″.

    Since you so brillantly gave us the ratios for the batter I don’t wanna screw it up by having too much batter in the pan.


  • 25 megan // Mar 8, 2012 at 12:07 pm

    Amanda – My pan is a 10×4, the bottom interior section is about 2.75 inches wide and I only filled the pan about half way full. So maybe your pan will work? I had no idea angel food cake pans come in three different sizes!

  • 26 Adrienne // Mar 10, 2012 at 6:22 pm

    You know, one of the loaf pan experiments took on a Peacock feather flair…could be lovely in shades of purple, blue, and green…

    What I am really curious to know is how much the food coloring affects the taste of the cake, if at all. Any thoughts from anyone? I want to make a rainbow cake for St. Patty’s Day next week, but I can’t help but wonder.

    Thank you for all the pan research you did – very helpful!

  • 27 Erika // Mar 14, 2012 at 3:57 am

    Thanks so much for all the experimentation! I covered mine in tinted coconut which was faster and easier for me:

  • 28 Alainna DePoalo // Mar 14, 2012 at 11:17 am

    I prepared this cake for the first time with a bundt because I don’t have an angel food cake pan. I’m excited to see the results. Though, my lines were squiggled all around. No matter, it will be cute! Thanks for the baggy idea for dying the cake colors.

  • 29 Amanda Meehan // Mar 16, 2012 at 12:37 pm

    Hi Megan, Well, mine didn’t come out the same in the smaller pan. I’m going to use smaller portions tonight when I make mine for the contest. With the remaining frosting I am going to make a few cupcakes on the side with just the batter layered. Anyway, I posted my pics on FB to share. I didn’t do the “trap” and I changed the frosting to just white. I have to admit, I do like the green for the color balance effect though. So excited I found your blog! Thanks for sharing all your techniques and tips!

  • 30 Amanda Meehan // Mar 16, 2012 at 12:37 pm

  • 31 Leprechaun Trap Cake // Jan 25, 2013 at 1:22 am

    […] baked rainbow cakes in a bunch of different shapes of cake pans and took photos of the results. Turns out? The rainbow arch effect works best in the angel food […]

  • 32 Lynette // Mar 12, 2013 at 8:26 am

    thank you so much. I appreciate all your trouble. I can’t wait to do this for my daughter. She will be 33 and will love it as much as she would have at the age of 13. Its just terrific.

  • 33 Lori Beth // Mar 14, 2013 at 9:56 am

    Hi, I have a donut cake pan, that comes out in a perfect dome. Have you tried this at all? I wonder if this would turn out or not. I might have to give it a try.

  • 34 Lucy // Mar 16, 2013 at 9:35 am

    I love this idea…and my daughter wants it for her 6th birthday which is also St Patty’s day theme. I bought a bundt cake pan for it, as I found your site last week, and did not read it closely enough to see that it was an angel food cake… I think I will return and buy the right one today. I cannot mess up my daughter cake. Your site it great.

  • 35 Sarah D // Mar 20, 2013 at 7:23 pm

    I bake a lot of cakes, a trick I learned from my mother in law who bakes cakes professionally is to put a baking dish of water in your oven as you preheat it. Leave the dish with water on your bottom rack and bake your cake like normal. It keeps it from doming up on top and it doesnt effect the baking.

  • 36 D // Sep 15, 2013 at 2:33 pm

    One reason for the volcano effect may be the pouring from height that you did, zen-like. It’s used when pouring soaps to get the colours to reach down into the batter for swirling, but in this case has apparently (because of no swirls) just buried some of the colours into the others = volcano

  • 37 megan // Sep 15, 2013 at 4:47 pm

    D – Huh. This needs further investigating. I’m going to have to do a high-pour and a low-pour version and see if they differ. Thanks for the insight!

  • 38 Jackie @ LovingLunches // Feb 6, 2014 at 3:22 pm

    I’ve been wanting to try this for some time now and with my little one’s birthday a week away she’s asked for Rainbow Dash cakes to take to Kindergarten – perfect excuse!
    Have you tried this in a cupcake? I’m thinking as you don’t upturn them and level off, if you kept the proportions but reversed the pour order would that work?
    Thank you!!!

  • 39 megan // Feb 6, 2014 at 3:29 pm

    Jackie – I have not tried these in a cupcake, but please report back on what your findings are!

  • 40 Jackie @ LovingLunches // Feb 9, 2014 at 6:10 am

    My first go I think they turned out OK
    I just spooned the mix in, and eyeballed the quantity. I think if I’d piped it in neatly they would have worked out much more rainbow-y. All the more excuse to try again!
    (These were made in mini-muffin size)

  • 41 Leigh Anne // Mar 14, 2014 at 9:34 pm

    Have you ever tried laying the colors down backwards? Same quantities but laying them down purple first? Then if you bake at 325 for a small mound in theory the rainbow will be right side up and you can use the rounded top of the cake as the round of the hill, rather than a flat topped hill? Just a thought, I may give it a try for the heck of it.

  • 42 megan // Mar 16, 2014 at 11:16 am

    Leigh Anne – I see what you’re saying but I think the rainbow would be upside down in that scenario. Or am I missing something?

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