Behind the Formula: How We Approached Broad-Spectrum Protection for Sunbloom

Sunbloom, our in-house sun care line, started with a brief that’s harder to satisfy than it sounds: broad-spectrum protection that actually holds up, in a texture people will reapply without dreading it. Here’s a look at the formulation trade-offs behind it.

The Brief We Set for Ourselves

Sun care sits at an unusual intersection — it’s judged on both a hard, testable performance metric (SPF and UVA protection) and a highly subjective sensory one (does it feel good enough that people actually reapply it). A sunscreen that tests well on paper but sits heavy, leaves a white cast, or pills under makeup fails in the market even if the SPF number is right.

For Sunbloom, the target was broad-spectrum protection with a texture elegant enough to be worn daily, not just on beach days — because consistent, everyday use is what actually delivers real-world sun protection benefit.

Filter Selection: Balancing Protection and Feel

We evaluated filter systems against three criteria simultaneously: UVA/UVB coverage breadth, photostability, and sensory impact on the final texture. Organic filters generally offer better cosmetic elegance but require careful stabilization; mineral filters (zinc oxide, titanium dioxide) offer excellent broad-spectrum coverage and inherent photostability but can be harder to formulate into a lightweight, cosmetically elegant base without a white cast or heavy feel.

The tension is real: the filters that are easiest to stabilize aren’t always the ones people want to wear every day — and the ones people want to wear every day aren’t always the easiest to stabilize.

The approach that worked: combining filter types to cover the UV spectrum efficiently while keeping total filter load manageable for texture, then investing formulation effort into film formation and spreadability so the finished product wears lighter than its filter load alone would suggest.

Solving for Photostability

As covered in our SPF formulation mistakes post, photostability is one of the most common places sun care formulas lose real-world efficacy even when they test well initially. For Sunbloom, this meant validating not just initial UV absorbance, but performance after simulated sun exposure — testing the formula the way it will actually be used, not just as it exists in the jar.

Texture: Where Emulsion Science Meets Consumer Experience

Getting a high UV filter load into a texture that still feels lightweight required close attention to emulsion system and emollient selection — the same underlying science covered in our HLB and emulsifier blending post. A stable emulsion is the baseline requirement; a stable emulsion that also spreads evenly, absorbs at the right rate, and doesn’t pill under other products is the actual bar for a sun care product people will reach for daily.

What We’d Tell Other Formulators Tackling Sun Care

Don’t treat SPF number and wearability as separate problems — they’re solved together, and optimizing one in isolation usually costs you the other
Test photostability under real exposure conditions, not just initial absorbance readings
Invest in film formation early — an uneven film undermines both SPF performance and cosmetic feel simultaneously
Design for reapplication — a formula people are willing to reapply throughout the day delivers more real-world protection than a marginally higher SPF number that people avoid using

The Takeaway

Sun care formulation is a genuine balancing act between measurable protection and subjective wearability — and neither one can be sacrificed for the other without undermining real-world efficacy. Sunbloom’s development reflected that from the brief stage onward, treating texture and photostability as core performance requirements, not secondary polish.

Explore Sunbloom, or start a custom sun care development brief of your own with our formulation team.