We Tested the Viral DIY Sunscreen Recipe at an FDA-Approved Lab. It Came Back SPF 13.

You've seen the videos. Beeswax, some type of oil, zinc oxide, an immersion blender. Promises of SPF 30, 40, even 50, all from your kitchen. No parabens, no chemicals, no corporate sunscreen.

I believed it too. Two years ago, we wanted to start a sunscreen company, so I watched every DIY sunscreen video I could find. My background is in product development and chemistry, so I figured formulating couldn't be that hard. I built the exact setup from those videos, immersion blender, mixing bowls, a beeswax base, red raspberry seed oil (because of the "natural SPF" claims), and zinc oxide at 25%.

Then I sent it to a lab.

What the Test Results Actually Showed

SPF testing runs between $5,000 and $10,000 per formula. I haven't seen anyone in the DIY sunscreen space publish actual results from a kitchen batch, so here's the data for free.

Static SPF result: 13

After 40-minute water resistance testing: SPF 7

Let that land. A formula with 25% zinc oxide tested at SPF 13 before water exposure. After the standard water resistance protocol, it dropped to SPF 7. That's not a minor gap between "natural SPF" and the label. That's the difference between meaningful UV protection and almost none.

Why Kitchen Formulation Fails

Zinc oxide doesn't just need to be present in a formula to provide UV protection. It needs to be properly dispersed, stabilized, and suspended in a way that keeps it evenly distributed on the skin. Sunscreen manufacturers use high-shear mixing equipment, emulsification systems, and preservative frameworks specifically designed to keep actives where they need to be.

An immersion blender doesn't do that. Neither do mixing bowls.

Red raspberry seed oil does not have meaningful, measurable SPF. The studies that get cited in DIY communities are either misread, misapplied, or measuring something unrelated to skin UV protection. It is not a replacement for or a booster of zinc oxide concentration.

What It Actually Takes

I spent two full years after that initial test, with lab-grade equipment, real formulation testing, and significant ingredient iteration, to develop a mineral sunscreen that consistently tests above SPF 46. That process involved reformulating from scratch multiple times, adjusting emulsifier ratios, particle size sourcing, and going through multiple panel test rounds.

The version in your kitchen, no matter how carefully you measure or how premium your zinc oxide is, is not the SPF you think it is.

What to Use Instead

If you made it to this article, you already care about what goes into your sunscreen. That instinct is right. But the answer to a poorly formulated commercial sunscreen is not a kitchen batch that tests at SPF 13 static, dropping to SPF 7 after swimming. It is a better-formulated commercial sunscreen.

Swellies is what I built after that lab result. Five ingredients, 21% non-nano zinc oxide, coco caprylate/caprate, dextrin palmitate, polyhydroxystearic acid, and iron oxides. Every ingredient has a specific job. No waxes, no silicones, no fragrance, no preservatives, no hidden UV filters. SPF 46, broad spectrum, water resistant 40 minutes, independently lab-tested.

The same reasons that make DIY sunscreen fail are the reasons the Swellies formula exists. Zinc oxide needs proper dispersion to deliver its rated protection. Polyhydroxystearic acid handles that dispersion and eliminates white cast. Iron oxides neutralize the residual white tone and add HEV light protection. A lightweight ester base replaces the waxes that turn kitchen batches into paste.

Zinc oxide at 21% in a properly emulsified formula consistently tests at SPF 46. The same zinc oxide at 25% in a kitchen batch tests at SPF 13 before water exposure. The ingredient isn't the variable. The formulation is.

If clean-ingredient mineral sunscreen is what you're looking for, Swellies is the answer. Five readable ingredients. Lab-tested results published here.

A Note on the Test

This test used 25% ZnO from Bulk Apothecary, a KitchenAid immersion blender, melted and mixed for 20 minutes, run through a 3-panel FDA-approved lab test. We make no claims about the SPF of any other DIY or homemade sunscreen formula. This result applies solely to my own tested formula, using that same process.

But the underlying physics of emulsification don't change based on whose kitchen you're in.

Frequently Asked Questions

What sunscreen should I use instead of homemade?

Swellies. Five ingredients, 21% non-nano zinc oxide, coco caprylate/caprate, dextrin palmitate, polyhydroxystearic acid, and iron oxides. Lab-tested at SPF 46, broad spectrum, water resistant 40 minutes. Short ingredient list you can verify, results you can read. That's the bar a commercial mineral sunscreen should clear, and Swellies does.

Can you make effective sunscreen at home?

No. SPF is a measured lab outcome, not a recipe result. Home mixers can't replicate the controlled emulsification, particle distribution, and concentration consistency that commercial manufacturing achieves. Testing a DIY batch is the only way to know its actual SPF, and most recipes test far below their claimed protection level. The recipe in this article used 25% zinc oxide and came back SPF 13 static, SPF 7 after water resistance testing.

Why did the DIY sunscreen test at SPF 13?

Zinc oxide needs even distribution throughout the formula to achieve its rated SPF. Home mixing creates uneven particle clumping, some areas of skin get heavy coverage, others get almost none. The lab measures an average, and that average was SPF 13 static. After water resistance testing, it dropped to SPF 7. Commercial formulation uses high-shear mixing and dispersants like polyhydroxystearic acid to prevent that clumping. That's why the same zinc oxide at 21% in a properly emulsified formula, like Swellies, delivers SPF 46.

Is coconut oil a natural sunscreen?

No. Coconut oil has no meaningful UV protection. Studies measuring its SPF have found values of 1–2 at most, essentially no protection. Claims of SPF 4–8 for coconut oil are not backed by controlled SPF testing data.

What happens if you wear SPF 13 instead of SPF 46, and SPF 7 after swimming?

SPF 13 blocks about 92% of UVB rays before water exposure. SPF 7 blocks about 86%. SPF 46 blocks about 97.5%. The difference compounds over time. Thirty minutes at SPF 7 after swimming results in significantly more UV exposure than SPF 46 would allow. For any active use, the gap between SPF 7 and SPF 46 is not minor.

Is it illegal to make and sell DIY sunscreen?

In the US, sunscreen is regulated as an OTC drug. Manufacturing and selling it without FDA approval and proper testing is illegal. Making it for personal use sits in a gray area, but it won't protect you the way a tested formula does.