Cake Postcard tutorial via She Knows Living:
Malleable cake postcard
Make a malleable slice of cake! This 3D cake postcard is 100% malleable. The postage is around $3 per slice but the reaction from the recipient is priceless.
Gather the supplies
These supplies will make 2 cake postcards: 1 large sponge, serrated knife, X-Acto or utility knife, spray paint, 1 tube acrylic latex caulk, spray adhesive, scrapbook paper.
Cut the sponge
With a serrated knife and using a sawing motion, cut a sponge in to two, cake wedge shapes to make the postcard. Large sponges can be found at hardware stores and in the automotive departments of most big discount stores.
Cut a center groove in the sponge
Using an X-Acto or utility knife, cut a section of foam from the center of the sponge. It’s 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
Paint sponge wedges with desired color. (Brown looks the most realistic, but pink and yellow are fun too. White was probably my least favorite.)
Trace around the shape
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. 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
Spray glue the postcards to the solid, flat sides of the sponge cake wedges.
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.
Pipe the center groove
Pipe a line of caulk down the center of the cake wedge, where you removed the sponge with your X-Acto or utility knife.Top of Form
Pipe the top of the cake
Pipe 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.
Allow to dry
Allow your cake postcards to dry for 3-5 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.
Write your message
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, $1.00 stamps.
Send it off!