If you're a DIY natural-beauty type, sunscreen is probably on your make-it list, or about to land on it. You can take a class to learn to make your own mineral sunscreen with zinc oxide (a highly effective natural physical UV filter), or search the Internet for recipes. But -- and this shouldn't be a surprise -- there are risks with a homemade formula.
A good mineral sunscreen is about more than the amount of zinc oxide you use, says Alain Ménard, co-founder of Green Beaver, a Canadian natural body-care line that includes UV protection. "Seemingly similar formulations with the same percentage of zinc oxide gave us very different SPF levels," he says of the company's early prototypes. Mineral sunscreen efficacy is affected by all sorts of factors, including its pH balance, its ability to cover skin evenly, and how well its ingredients stay together. A texture you like is also important.
the float factor
Zinc oxide is a weighty mineral that likes lazing around on the bottom of containers. Keeping it suspended and stable in your formula is key to achieving even coverage. "If the zinc is unstable, the sunscreen won't be effective at all," says Alain. "If the zinc is badly dispersed, you could end up with burn spots, or with an extremely low SPF that would give you, say, only 30 minutes of protection." To get it right, you need a base cream or lotion with a pH balance between 7.0 and 8.5.
the protection factor
If you manage to solve the sinking/instability issues, you still have another obstacle: unless you have your final product tested, you just don't know the level of SPF you're getting.
the cheat factor
Still determined to make your own mineral sunscreen? Okay. If you find a natural sunscreen recipe that calls for a cheat – as in using a zinc diaper cream as your starting point – Alain says you might be all right. Look for a formula that is at least 40% zinc oxide (try Zincofax or Desitin Maximum Strength), and dilute it using only oils or waxes. "Don't put water in the formula," cautions Alain. "Water can change the pH, which could de-stabilize the zinc."
Make sure the diaper cream is 50 percent of the overall mixture. You'll be left with a 20-percent zinc content, which should deliver decent UV protection. As well, mix the formula thoroughly to ensure even coverage. "You'll be able to see whether it's mixed well because zinc diaper cream is quite white. You'll see bare spots on your skin if your blending is uneven," says Alain. Obviously, achieving an utterly transparent DIY mineral sunscreen is a bit tricky. And good luck on the texture.
the damage factor
One more thing to remember: sunburn may be the most obvious sign of sunscreen fail, but a tan, even if acquired without a trace of redness or discomfort, is sun damage too.
As for me, although the make-your-own-mineral-sunscreen idea is interesting, I prefer the safety assurance that comes with properly tested formulas.
Have you ever made your own sunscreen? Would you?