Fill a quart sized Ziploc bag with shaving cream. (We get ours from the dollar store. They're one size bigger than sandwich bags).
Add the cornstarch to the bag.
Then add 5 - 10 drops of food colouring to the bag.Pink, green, and blue should be fine with fewer drops. Red and yellow require more drops to create vibrant colours.
Seal the bag, taking out as much air as possible, and begin kneading it.Keep squishing the bag around until the contents are completely mixed and there aren't any dark spots of colour.
Step 3: Add paint to a squeeze bottle (optional)
Cut a small hole in a bottom corner of the bag and transfer the paint into a squeeze bottle.Note: You can also squeeze the paint right out of the plastic bag onto the pavement and skip the plastic bottle!
Cut off part of the plastic lid to make a bigger opening. The bigger the opening, the easier (and puffier!) it is to paint.Repeat for as many colours as you'd like to make. A plain white paint is also fun!
Step 4: Enjoy your puffy sidewalk paint
Go outside to paint on the sidewalk or driveway. Choose your first colour and squeeze the bottle to apply the paint.
Depending on the size of the opening in your bottle, your lines may be thinner than you'd like. You can use the tip of the bottle or a popsicle stick to spread out the paint if needed.