Natural Sunscreen Ingredients: What DIY Formulators Need to Know

Making your own body butter, lotion or facial moisturiser can be a rewarding way to learn cosmetic formulation. Sunscreen, however, belongs in a very different category.

Although ingredients such as zinc oxide and titanium dioxide are available to home formulators, simply adding one of these powders to a lotion does not automatically create a reliable sunscreen. Effective sun protection depends on the complete formulation, including the UV filter grade, concentration, particle dispersion, film formation, stability and the amount applied to the skin.

Most importantly, the finished product must undergo recognised laboratory testing before its sun protection factor, UVA protection or water resistance can be known.

This guide explains how mineral UV filters work, what “nano” and “non-nano” mean, why homemade SPF cannot be calculated from an ingredient percentage, and what South African formulators should consider before developing or selling a sun-care product.

Important: This article is intended for cosmetic formulation education only. It does not provide a tested sunscreen formula or replace professionally manufactured, laboratory-tested sun protection.

Why Sun Protection Matters in Southern Africa

Sun exposure across South Africa, Namibia, Botswana and neighbouring countries can be significant throughout much of the year. Reliable sun protection should therefore be part of an everyday routine rather than something reserved only for holidays or summer.

People interested in natural skincare may be drawn to mineral sunscreens because they would prefer to avoid fragrance or particular organic UV filters. Others may want greater control over the oils, emollients and sensory ingredients in their skincare products.

That interest is understandable, especially once you have gained experience with a simpler product such as a natural body butter recipe. However, sunscreen is substantially more technically demanding than a body butter or ordinary moisturising lotion.

A body lotion can be evaluated for properties such as appearance, skin feel, viscosity and emulsion stability. A sunscreen must also produce an even and sufficiently protective film over the skin and demonstrate verified performance against ultraviolet radiation.

Can You Make a Reliable Sunscreen at Home?

Zinc oxide and titanium dioxide are established mineral UV filters. However, having a recognised UV filter in a formulation does not tell you the SPF of the finished product.

Sun protection depends on factors including:

• The type and grade of UV filter used
• The filter’s concentration
• The size, shape and surface treatment of its particles
• Whether the particles are properly dispersed
• Whether particles clump together or settle during storage
• The oils, emulsifiers and film-forming ingredients in the formulation
• How evenly the product spreads over the skin
• How much product is applied
• Whether the formulation remains stable over time
• Whether the protective film is disrupted by water, sweat or rubbing

These variables cannot be assessed by looking at a lotion or checking whether it leaves a white cast.

Professional sunscreen testing uses standardised methods to evaluate the finished formula. South African testing providers refer to ISO 24444 for in-vivo SPF determination, ISO 24443 for UVA photoprotection and SANS 1557 in relation to sunscreen products in South Africa. Water-resistance claims require additional testing. [sgs.com], [futurecosm…tics.co.za], [futurecosm…tics.co.za]

For this reason, a homemade product should not be relied upon as a replacement for a commercially manufactured and appropriately tested sunscreen.

Benefits and Limitations of DIY Mineral Sun-Care Formulation

Experimenting with mineral dispersions can be educational for experienced formulators. It may help you learn about wetting powders, managing viscosity, creating stable emulsions and improving the skin feel of products containing insoluble particles.

However, an experimental mineral lotion is not automatically a sunscreen.

What DIY formulators can do

A formulator can:

• Learn how zinc oxide and titanium dioxide behave in different oils
• Compare coated and uncoated cosmetic grades
• Evaluate white cast and skin feel
• Practise pre-dispersing powders
• Conduct preliminary emulsion-stability checks
• Measure and adjust pH where appropriate
• Send a professionally developed formulation for laboratory testing

What DIY formulators cannot determine at home

Without suitable testing, a formulator cannot reliably determine:

• The product’s SPF
• Its level of UVA protection
• Whether it qualifies as broad spectrum
• How long protection will last
• Whether it is water resistant
• Whether any particular percentage of zinc oxide will produce a specific SPF
• Whether the product provides even protection across the application area

There is no dependable home calculation that converts a percentage of zinc oxide or titanium dioxide into an SPF number. Recognised testing evaluates the finished formulation, not only the amount of UV-filter powder included. [sgs.com], [futurecosm…tics.co.za], [scienceinsights.org]

Natural Sunscreen Ingredients – How Mineral UV Filters Work

Zinc oxide and titanium dioxide are commonly described as “physical blockers” that sit on the skin and reflect sunlight like tiny mirrors. This popular explanation is incomplete.

Mineral UV filters protect the skin primarily by absorbing UV radiation, while also scattering and reflecting a portion of incoming light. Their behaviour depends partly on particle size and the formulation in which they are dispersed.

Organic UV filters, sometimes casually called “chemical filters,” also protect largely by absorbing UV radiation. Using “mineral” and “organic” is therefore generally more useful than implying that one category absorbs UV while the other only reflects it.

It is also worth remembering that every cosmetic ingredient is a chemical substance, including water, zinc oxide, botanical oils and naturally occurring minerals. The word “chemical” does not automatically mean unsafe or undesirable.

Zinc Oxide in Sun-Care Formulation

Zinc oxide can provide protection across UVA and UVB wavelengths when used in a properly designed and tested formulation. This broad coverage is one reason it is frequently used as the principal filter in mineral sunscreens.

However, zinc oxide can introduce several formulation challenges:

• A visible white or grey cast
• A thick or draggy skin feel
• Particle agglomeration
• Settling or uneven distribution
• Increasing viscosity over time
• Interactions with emulsifiers and other ingredients
• Difficulty obtaining an even film on the skin

A lotion that appears smooth to the naked eye may still contain microscopic areas of uneven particle distribution. Professional sunscreen manufacturers use suitable raw-material grades, dispersion technology and controlled manufacturing processes to achieve more uniform results.

Titanium Dioxide in Sun-Care Formulation

Titanium dioxide is another established mineral UV filter. It is particularly effective across UVB and shorter UVA wavelengths, while zinc oxide generally provides broader UVA coverage.

Some professionally formulated mineral sunscreens use both zinc oxide and titanium dioxide. This allows the formulator to balance UV coverage, appearance, texture and the overall amount of mineral material in the formula.

As with zinc oxide, titanium dioxide must be a cosmetic grade intended for the selected application. Its presence does not allow the formulator to predict the finished product’s SPF or broad-spectrum performance.

Nano and Non-Nano Zinc Oxide

The terms “nano” and “non-nano” relate to particle dimensions, but product descriptions do not always tell the complete story. Powders may contain a distribution of particle sizes, and individual primary particles can form larger aggregates or agglomerates.

Smaller mineral particles can reduce visible whitening, which is why some commercially formulated mineral sunscreens are more transparent on the skin. Larger particles are generally more visible and may produce the characteristic white or grey cast associated with mineral products.

Many natural-product customers prefer non-nano zinc oxide because they wish to avoid nanomaterials. However, it is better to present this as a formulation and consumer preference rather than claiming that non-nano zinc oxide is universally safer or more effective.

When sourcing zinc oxide, ask the supplier for documentation relevant to the grade, which may include:

• INCI name
• Intended cosmetic application
• Certificate of analysis
• Safety data sheet
• Particle-size information
• Purity specification
• Surface-treatment information
• Microbiological or heavy-metal specifications where applicable
• Guidance regarding dispersion and recommended processing

Avoid industrial grades intended for rubber, paint, ceramics or other non-cosmetic applications.

Does a White Cast Prove That a Product Is Working?

No. A visible white cast shows that mineral particles are present and interacting with visible light. It does not prove that the product has a particular SPF, provides sufficient UVA protection or has formed an even protective film.

An unevenly dispersed lotion may look very white while leaving microscopic gaps in coverage. Conversely, a professionally formulated product may appear relatively transparent because of the selected particle grade and dispersion technology.

Appearance cannot replace efficacy testing.

Can Carrier Oils Provide Natural SPF?

Online recipes sometimes claim that coconut oil, raspberry seed oil, carrot seed oil or other botanical oils have substantial natural SPF values.

These ingredients may be useful as emollients or antioxidant-supporting components in cosmetic formulations. They should not, however, be treated as standalone sunscreen actives or relied upon to provide predictable sun protection.

The composition of natural oils can vary according to cultivar, growing conditions, extraction method, refining and storage. Even where laboratory measurements suggest some UV absorbance, that does not establish a dependable SPF for the oil when applied to human skin.

Carrier oils should therefore be selected for properties such as:

• Oxidative stability
• Skin feel
• Spreadability
• Compatibility with the UV-filter dispersion
• Suitability for the intended user
• Contribution to the final product’s sensory profile

If you are learning to select suitable emollients, our guide to jojoba oil in skin formulation provides a useful starting point.

Why an Emulsifier Alone Is Not Enough

A water-containing mineral lotion needs a suitable emulsification system to combine its oil and water phases. The emulsifier helps create an emulsion, but it does not automatically guarantee that zinc oxide or titanium dioxide will remain uniformly dispersed.

UV-filter powders may require:

• Pre-dispersion in a suitable compatible medium
• Appropriate wetting agents
• Suitable dispersants
• Controlled mixing or homogenisation
• Viscosity management
• Suspension support
• Compatibility testing
• Stability testing in the final packaging

A stable-looking emulsion can still contain poorly distributed mineral particles. Likewise, a lotion that does not visibly separate may still undergo settling, agglomeration or performance changes during storage.

Our guide to choosing an emulsifier for stable lotions and creams explains the general role of emulsifiers. Formulators should nevertheless avoid assuming that an emulsifier suitable for an ordinary moisturiser will automatically be suitable for a sunscreen formulation.

An oil-to-milk product made with an ingredient such as Durosoft PG4-O oil-to-milk emulsifier may offer an appealing cleansing or rinse-off sensory profile, but it should not be assumed to create a water-resistant sunscreen film. Product format, wash-off behaviour and sun-protection performance are separate considerations.

If you are new to emulsion formulation, work through our beginner’s guide to skincare formulation before attempting advanced mineral dispersions.

Preserving a Water-Containing Mineral Lotion

Any formulation containing water requires an appropriate preservation strategy.

Vitamin E is an antioxidant. It can help delay oxidation in oils, but it is not a broad-spectrum preservative and does not protect a water-containing product against bacteria, yeast and mould.

When choosing a preservative, consider:

• The supplier’s recommended usage rate
• The effective pH range
• Whether it is added during heating or cool-down
• Compatibility with the emulsion and mineral ingredients
• The amount of water in the formula
• Packaging and expected consumer use
• Whether the formulation contains ingredients that may increase microbial risk

Statements such as “add 1% preservative” are not universally appropriate. Preservatives have different usage ranges and processing requirements.

The finished product’s pH should be measured using a calibrated pH meter and adjusted only where necessary and compatible with the complete formulation. The target pH must fall within the preservative’s effective range while remaining suitable for the product and its other ingredients.

You can review DIY Naturally’s available preservative options for cosmetic formulation, but always follow the documentation for the specific preservative selected.

For a product intended for sale, professional microbial testing should form part of product development. Depending on the product and intended market, this may include microbial quality testing and preservative efficacy or challenge testing.

Safe Handling of Zinc Oxide and Titanium Dioxide Powders

Fine cosmetic powders should be handled carefully to minimise airborne dust.

Good handling practices include:

• Working in a clean area with suitable ventilation
• Avoiding actions that create airborne powder
• Wearing appropriate respiratory protection where required by the supplier’s safety documentation
• Using suitable gloves and eye protection
• Keeping powder containers closed when not in use
• Cleaning spills without sweeping dry powder into the air
• Following the supplier’s safety data sheet
• Avoiding the use of spray or aerosol formats

A finished lotion presents a different exposure pattern from loose airborne powder, but safe raw-material handling remains essential during manufacturing.

Testing Required for a Sunscreen Product

Visual checks, pH readings and home stability observations are useful during development, but they cannot establish sunscreen efficacy.

Depending on the product and the claims being made, professional evaluation may need to address:

• SPF performance
• UVA protection
• Broad-spectrum performance
• Water resistance
• Formula stability
• Packaging compatibility
• Microbial quality
• Preservative efficacy
• Relevant safety and tolerability considerations

South African sunscreen testing services identify recognised methods including ISO 24444 for SPF, ISO 24443 for UVA photoprotection and standards for water-resistance assessment. SANS 1557 is also referenced for sunscreen products in South Africa. [sgs.com], [futurecosm…tics.co.za], [futurecosm…tics.co.za]

An untested formula must not be assigned an SPF based on its zinc oxide percentage, a supplier’s theoretical estimate or the SPF of another product containing similar ingredients.

Selling Sun-Care Products in South Africa

Claims such as “SPF 30,” “broad spectrum,” “UVA protection,” “all-day protection” and “water resistant” require appropriate substantiation.

Rather than describing every SPF product as automatically becoming a medicine or therapeutic product, the more reliable practical principle for South African small businesses is this:

Do not place an SPF number, broad-spectrum claim, water-resistance claim or equivalent sun-protection promise on a product unless the finished formulation has been appropriately tested and the labelling and marketing have been reviewed against the requirements applicable to that product.

Calling an untested product “sun protective,” “sun shield,” “UV defence” or “mineral sun lotion” may still communicate an efficacy claim. Avoiding an SPF number does not necessarily remove the need to substantiate what the marketing implies.

The product’s name, imagery, instructions, website description, social-media advertising and customer communications should all be considered, not only the words printed on the label.

Anyone planning to commercialise a sun-care product should obtain current regulatory guidance and work with an experienced cosmetic formulator and suitable testing laboratory. Our guide to starting a natural beauty business in South Africa provides broader business-planning information, but sunscreen-specific testing and compliance should be addressed separately.

What Should You Use for Dependable Daily Sun Protection?

Where dependable protection is needed, use an appropriately tested, correctly labelled sunscreen and follow its application instructions.

Sun protection should also include sensible exposure-management measures, such as:

• Seeking shade
• Wearing protective clothing
• Using a broad-brimmed hat
• Protecting the eyes with suitable sunglasses
• Limiting unnecessary exposure during periods of intense sunlight
• Reapplying sunscreen as directed on the tested product
• Reapplying after swimming, sweating or towelling where directed

No homemade product should be assumed to be water resistant. Water-resistance is a performance claim requiring specific testing. [sgs.com], [futurecosm…tics.co.za]

Extra caution is appropriate for babies, children, people using photosensitising medication and anyone with a history of skin cancer or a medical condition affected by sunlight. Advice for these individuals should come from a qualified healthcare professional.

Frequently Asked Questions

Can I calculate SPF from the percentage of zinc oxide?

No. The percentage of zinc oxide alone cannot determine the SPF of a finished product. Dispersion, particle grade, film formation, application thickness, stability and the rest of the formulation all influence performance. SPF must be established through recognised testing of the finished formula. [sgs.com], [futurecosm…tics.co.za], [scienceinsights.org]

Does 10% zinc oxide equal a particular SPF?

No dependable SPF can be assigned to a formula solely because it contains 10% zinc oxide. Rules of thumb that convert zinc oxide percentage into an SPF number should not be used for product labelling or consumer protection decisions.

Is zinc oxide better than titanium dioxide?

Neither ingredient is automatically “better” in every formulation. Zinc oxide generally provides broader UVA coverage, while titanium dioxide is particularly useful across UVB and shorter UVA wavelengths. A formulator may use one or both, depending on the desired performance, texture and appearance. The finished product must still be tested.

Is non-nano zinc oxide safer than nano zinc oxide?

It is not appropriate to make a universal safety comparison based only on the words “nano” and “non-nano.” Many consumers and natural-product formulators prefer non-nano grades, while smaller particles may reduce visible whitening. Use cosmetic-grade material, review the supplier’s documentation and choose a grade appropriate to the intended product and applicable requirements.

Does a white cast mean the product provides good UV protection?

No. White cast is a cosmetic and optical effect. It does not establish SPF, UVA protection, broad-spectrum performance or even particle distribution.

Can raspberry seed oil, carrot seed oil or coconut oil replace sunscreen?

These oils can be useful cosmetic emollients, but they should not be relied upon as alternatives to a professionally tested sunscreen.

Is vitamin E a preservative?

No. Vitamin E is primarily used as an antioxidant in the oil phase. It does not provide broad-spectrum antimicrobial preservation for a water-containing product.

Can I label an untested product “sun protective” if I leave off the SPF number?

That wording may still imply UV-protection performance. Product names, descriptions, images and instructions can all create claims. Obtain appropriate regulatory advice before marketing an untested product using sun-protection language.

Can I sell a mineral sunscreen in South Africa?

A sun-care product intended for sale requires a properly developed formula, substantiated claims, appropriate testing and compliant labelling. South African testing providers offer SPF, UVA and water-resistance assessment using recognised methods. [sgs.com], [futurecosm…tics.co.za], [futurecosm…tics.co.za]

Final Thoughts

Zinc oxide and titanium dioxide are legitimate mineral UV filters, but access to these ingredients does not make reliable sunscreen simple to manufacture at home.

The most important lesson for DIY formulators is that sunscreen performance belongs to the finished, tested formulation, not to a single ingredient. A mineral powder’s percentage, white cast or presence on a supplier’s product list cannot reveal the SPF of the final lotion.

DIY Naturally supports learning, responsible ingredient sourcing and evidence-based formulation. We stock cosmetic ingredients and emulsifiers for lotion development, but we encourage formulators to recognise when a product moves beyond ordinary DIY skincare and requires professional development and testing.

Experiment with lotions and mineral dispersions to build your formulation skills, but rely on an appropriately tested sunscreen when genuine sun protection is required.

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