Okay, you all probably know by now that I like simple recipes with as few ingredients as possible. That way, it's easier to tell if any of the ingredients is causing problems / clogs. This recipe has two ingredients: hemp oil and zinc oxide.
To make 2 ounces of sunscreen with 20 SPF:
Approximately 2 ounces of hemp oil
0.4 ounces of zinc oxide (measured on a kitchen scale)
Mix together in a non-metal vessel and then pour the sunscreen into a PET container. Keep in the fridge!
You can adjust the measure of zinc oxide in the recipe according to your desired SPF. The percentages are of the total weight of the final product.
For SPF 2-5: Use 5% zinc oxide
For SPF 6-11: Use 10% zinc oxide
For SPF 12-19: Use 15% zinc oxide
For SPF >20: Use 20% zinc oxide
Choosing the Zinc OxideThe most important factor to consider when choosing your zinc oxide is the size of the particles. A lot of products use Nano or Micronized zinc oxide, which is an ultrafine powder that turns clear when applied. Unfortunately, nanoparticles have been found to cause health problems because they are so small that they can enter the body through the skin.You want a particle size of MORE THAN 100 nm.
How it worksZinc oxide is a physical barrier sunscreen. This means that it creates a barrier on your skin that blocks UVB and UVA rays (Murphy 1999).
Here's a great article explaining the mechanisms of sunblocks:
Sunblocks: Mechanisms of action