Materials Needed:

1. Empty Size 00 Capsules:These capsules contain the foam shapes and the fizzing solution.
2. 1/2" Low-Density Foam:Available at many craft or fabric stores, or other stores that specialize in upholstering supplies. This can either be bought as colored or plain white sheets. Be sure to get the spongy type of foam you would use for upholstery, not the dense craft foam sheets that are often used in scrap-booking. (Note...1" sheets may be easier to find than 1/2" sheets of upholstery foam...I used 1" foam and cut out 2" foam squares, then cut them in half with scissors to create two 2" x 1/2" foam squares.) 
3. Citric Acid:Citric acid is the natural chemical that makes foods such as lemons and limes taste sour. It is available for flavoring at many candy and baking supply stores. It also can be found in grocery stores and pharmacies. This is used to create the fizzing solution. One teaspoon will be needed for this recipe.
4. Baking Soda:Available at any grocery store. This is also used to create the fizzing solution. One tablespoon will be needed for this recipe.
5. Essential Oils:Used to give your capsules a unique aroma. About 6-10 drops are needed for this recipe (which makes between 50 and 100 capsules, depending on how much powder is used in each capsule).
6. Other Materials Needed:straw (used to help put the foam shapes in the capsules—the larger diameter ones like they give with drinks at many fast-food locations such as Sonic or McDonald's fit perfectly in the size 00 capsules), small dowel (used to help compact the foam shape into the capsule—just needs to be smaller in diameter than the straw), cutting materials (used to cut the foam into shapes—I used scissors, craft knives, paper-punches, and die-cutting machines to make the foam shapes and letters used in the photos on this page), a small bowl (to mix the fizzing powder in), a small wooden stick (to stir the fizzing powder), and food coloring (optional—to color the foam shapes if desired).

	Use scissors, an Exacto knife, paper-punches, or die-cutters to cut shapes or letters out of the foam. Solid shapes up to about 1-1/2" in diameter will fit easily into the capsules. Many craft and scrap-booking supply places sell paper die-cutting tools and systems that work really well to cut out intricate small shapes from the foam (I used ones available locally made by Sizzix, but other brands may be available in different locations—I also cheated a bit and just bought the dies (such as the green moon-shaped die at left) and used a rubber mallet to pound the dies through the foam on a cutting mat. This was much less expensive than buying the complete die-cutting tool). I also had success using large paper-punches (such as the yellow star punch shown at left) to punch shapes from the foam. If you do this, fold an index card in half, flatten a small square of foam between the two sides of the card, then insert the folded edge of the card (with the foam in the middle) into the paper punch and punch out the shape. Remove the card and foam, then remove the shape. If you don't have access to either of these types of tools, a good pair of scissors or a sharp Exacto knife can be used as well to create your shapes. If desired you can color your foam shapes by dipping them in a small cup containing 3-5 drops of food coloring mixed in 1 tablespoon of water. Compress the foam a few times until the foam is saturated with the colored liquid, then lift the foam and squeeze out the excess liquid (this can be messy, so you may want to use gloves or a plastic back to lift and squeeze the foam shape). Allow the foam shape to dry overnight.
	Create the fizzing powder by mixing 1 tablespoon of baking soda with 1 teaspoon of citric acid until well combined. Add 6-10 drops of your desired essential oil or blend and mix thoroughly. Open a capsule and fill the larger half about 1/4 to 1/3 of the way full with the fizzing powder.
	Starting with the narrowest side of a shape, squeeze and insert a foam shape into one end of a large drinking straw. Twisting and pushing the shape into the straw at the same time can make it easier to insert some larger shapes. When the shape is mostly inside the straw, insert the other end of the straw into the larger-half of the capsule that has the fizzing solution in it.
	Use a small dowel or stick to push the foam shape into the capsule. Hold the shape in the capsule with the dowel while you remove the straw. Hold the shape in the capsule with your fingers, and place the small half of the capsule over the larger half and push the two halves together until the capsule is closed. (If desired, and if you have enough room, you can also add a bit of the fizzing powder to the small half of the capsule before you close it...the more fizzing powder you add, the more fizzing action you'll get when the capsule opens, but you'll also have to use smaller shapes to accommodate more powder).
	Repeat the steps above to create more capsules. To use the capsules, place in warm water and wait for a few minutes. The capsule will be dissolved by the water and begin to open soon. Caution: Do not swallow capsules. Do not allow children three and under to play with the capsules or the foam shapes contained within them. If desired, package your capsules in small plastic bags or bottles to give away as gifts. Create a label, card, or tag for your capsules listing the scent and directions for use. Be sure to include the caution above.

 

Extra Ideas:

For a fun gift, create capsules containing the letters of the alphabet that spell the name of the recipient. Create capsules with letters of the alphabet that create a word that someone must unscramble. Make capsules with clues inside them that will lead an individual or group on a treasure hunt (great for kids parties!). Make the scent part of the clue for an even greater challenge.