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Cake postcard tutorial

I have so many friends and family members that always say “I wish you could mail me a birthday cake!”… well, now I can mail them a slice.

cake postcards

Make a mailable slice of cake

I have so many friends and family members that always say “I wish you could mail me a birthday cake!” … well, now I can send them a slice.

Imagine how happy and excited you’d be, if you went to your mailbox one day and pulled out a slice of cake. Now you can surprise friends and family (and probably even your mail carrier), with this three-dimensional, mailable postcard, cleverly disguised as cake. With only five ingredients in this crafty recipe — a large sponge, spray paint, caulk, spray adhesive and heavy paper — it’s a piece of cake. Literally. Postage is around $3 per slice, but the reaction from the recipient will be priceless.


Materials needed to make two cake postcards:

  • 1 large sponge (yellow paints the best)
  • Serrated knife
  • X-Acto or utility knife
  • Spray paint (brown, yellow, pink or white)
  • 1 tube acrylic latex caulk (brown, cream or white)
  • Spray adhesive (3M Super 77 works great!)
  • Cardboard, kraft paper or scrapbook paper



Cut sponge into wedge shape

Postcard Cake Step 1: cut the sponge

With a serrated knife, using a sawing motion, cut a sponge into two, cake wedge shapes. Large sponges can be found at hardware stores and in the automotive departments of most big discount stores.


Cut a center groove into sponge

Postcard Cake Step 2: cut center of sponge

Using an X-Acto or utility knife, cut a section of foam from the center of the sponge. It doesn’t have to be perfect. Just cut a wedge big enough so that you can add a line of caulking there later.


Paint the sponge

Postcard Cake Step 3: paint the sponge

Paint the sponge wedges in desired color. (Brown looks the most realistic, but pink and yellow are fun too. White was probably my least favorite.)


Trace the slice of cake

Postcard Cake Step 4: trace around the sponge
When the sponge wedges are dry, trace around them on a piece of cardboard, kraft paper or colorful scrapbook paper. This will be the postcard side of the cake. Heavier paper works better and will give you a sturdier wedge of cake for mailing. Cut the postcard shapes from the paper.


Attach the postcard

Postcard Cake Step 5: attach the postcard

Spray glue the postcards to the solid, flat sides of the sponge wedges.


Prep the “icing”

Postcard Cake Step 6: add caulk to piping bag

Using a caulking gun and your desired caulk, fill a plastic disposable piping bag with half of the caulk. This should be enough to do one cake wedge. I was able to pipe two cake postcards with one tube of caulk, but I recommend putting only half of the caulk in the bag at a time. Also, I tried decorating my cake wedges using the caulking gun, but it was nearly impossible to control. It’s much easier with a piping bag.


Pipe the center of the cake

Postcard Cake Step 7: pipe the caulking

Pipe a line of caulk down the center of the cake postcard wedge, where you removed the sponge with your knife.


Pipe the icing on the top

Postcard Cake Step 8: pipe caulking on topPipe dollops and swirls of caulking on the top and sides of the sponge wedge just like you’re decorating a cake. Pipe along the edge of the cake postcard to form a seal between it and the sponge.


Add the swirls

Postcard Cake Step 9: swirl with paintbrush
If needed, use a small paint brush or toothpick to swirl and adjust the thickness of the caulk on the cake top and side.

Allow your cake postcards to dry for three to five days. I placed mine on sheet of parchment paper and lifted them up periodically so that the caulk wouldn’t dry and adhere to the paper.

Postcard Cake Step 9: let dry

Write your message on the postcard side, leaving enough room for an address and postage. Sizes, shapes and weight of each cake postcard will vary, but most of mine required three, $1 stamps.

Postcard Cake Step 9: back of cake postcard

Note from the editor

This totally works! I had Sandra mail me a slice of cake so I could see it with my own eyes. It made it to me in perfect condition. I could hardly believe it. See for yourself below:

Proof that you can in fact mail a slice of cake.

mailed cake postcard

Video how-to: Cake postcard

Not into diy?

Fear not! You can still have your cake and eat it, too. Check out this Etsy shop where you can purchase your very own mailable slice of cake.

Pumpkin pie postcard


Check out our
DIY pumpkin pie postcard tutorial

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