Homemade Sunscreen

Step 4: SPF Table

If using the zinc oxide or titanium dioxide separately, use the following table to determine your measurements.
I don't have a chart for using the blended powder, but it starts off with SPF35 on its own.  

For example, 8oz. (weighed) of lotion + .8oz of titanium micronized dioxide (weighed) = SPF20+
The Micronized TD is 10% of the original amount of lotion used (not the finished weight).

If you used 8oz of lotion + .8oz of Micronized ZO, the SPF would be 11-12.

If it's still too confusing, ask!

Concentration of Sunscreens & SPF	Low (SPF 2-5)	Moderate (SPF 6-11)	High (SPF 12-19)	Ultra High (SPF >20)
Titanium Dioxide	<4 %	8 %	12 %	20 %
Titanium Dioxide, Micronized	2 %	4 %	6 %	10 %
Zinc Oxide	5 %	10 %	15 %	25 %
Zinc Oxide, Micronized	3 %	7.5 %	12 %	20 %

_{This chart is to provided by my supplier. I can not do any testing internally. Just to be used as a guideline.}

Comments

[Roxanne_b]

Thank you for this instructable I'm very excited to try it!!

However I'm very confused . . . is the percentage the percentage of the lotion? so for example use 25% of the overall weight of the lotion zinc oxide and that would be SPF 20?

[Heptron]

I did some quick math in Excel and it seems that this table of data generates curves with exponential growth.
Do you know how well this hold true outside the data set?