Prepare your double boiler. If you don't have one, you can create one by filling a saucepan with several inches of water. Bring the water to a simmer. Then place a heat-safe glass bowl over the saucepan, making sure the bottom does not touch the water.
Add the grass-fed tallow, beeswax, and mango butter to a double boiler or heat-safe glass bowl and place it over the simmering water of the double boiler. Allow the ingredients to melt slowly over low heat, stirring occasionally until everything is fully melted and smooth.
1/2 cup grass-fed tallow, 2 tbsp beeswax, 1 tbsp mango butter
Once the tallow, beeswax, and mango butter are completely melted, carefully remove the mixture from heat. Stir in the calendula-infused oil until fully incorporated. If you are using vitamin E or any essential oils, you can add them now.
1/4 cup calendula-infused olive oil
Slowly whisk in the zinc oxide, stirring continuously until fully incorporated and no clumps remain. Be sure to mix thoroughly so the zinc oxide is evenly distributed throughout the diaper balm.
2 tbsp non-nano zinc oxide (uncoated)
Place the bowl in the refrigerator for 20–40 minutes, or until the mixture begins to firm up and becomes opaque but is not completely solid.
Using a hand mixer or stand mixer, whip the mixture for several minutes until it becomes lighter, smoother, and creamy.
Spoon or pipe the whipped diaper balm into clean jars or tins. I like to use these amber jars. Store in a dark place away from direct sunlight.