Two kinds of frosting are used, both the same color. A message is written with the Baking soda infused frosting, then regular frosting is poured in place to fill the spaces between.

To reveal the message, you spray it with lemon juice, it reacts to the written message with the baking soda, foams up and shrinks revealing the message which might be "It's A Boy!" or "It's A Girl!" "Happy Birthday!" or whatever.
-- doctorremulac3, Feb 27 2023

Ripped off from this idea. Wildfire_20inspired...20cake_20decoration
And wrecked just a little bit. [doctorremulac3, Feb 27 2023]

Baking soda might make the icing a little bitter.

Colourings that change according to the pH are however widely known to exist, so you could just have your special reveal icing change colour in reaction to the acidity of the lemon juice spray.

Not as spectacular as the foaming up maybe, but still allows the message to be revealed...
-- prufrax, Feb 27 2023


Yea, I know baking soda goes into certain, well, baking products, but there'd definitely need to be some experimentation to get the taste to be palatable.

And yea, anything that would work and not taste gross.
-- doctorremulac3, Feb 27 2023



random, halfbakery