Key takeaways
- Sticks are anhydrous, so they need no preservative and tolerate heat better than emulsions.
- A sunscreen stick must deliver 2 mg/cm² to reach its labelled SPF.
- Wax choice decides whether the stick glides or drags at 15 °C.
A stick is a solid suspension of powders and actives in a wax-oil matrix. It has almost no water, which makes it stable in a hot car, tolerant of freeze-thaw and free of preservatives. Those are real advantages for sunscreen, balm and spot treatments, and they come with a matching set of constraints that buyers discover after the first production run.
1. Structure and wax choice
The matrix is typically 15 to 25 percent wax and 60 to 75 percent oil, with powders and actives filling the remainder. Beeswax gives a firm stick that drags; a blend with ozokerite or polyethylene gives a smoother glide. The glide point matters: a stick that is comfortable at 30 degrees can be unusable at 15, which is why winter markets need a softer wax blend than summer markets.
2. Payload limits
Powders above 25 to 30 percent make the stick brittle and prone to breaking at the base. That caps how much mineral filter a sunscreen stick can carry, and it is the reason high-SPF mineral sticks are difficult to build. Chemical filters are liquid and easier to include, but they soften the matrix, so the wax ratio has to rise in step.
3. The application dose problem
SPF is measured at 2 mg per square centimetre. Most people apply a stick at less than half that, which means the labelled protection is rarely achieved in use. A stick can still be labelled SPF 50 if it passes the test, and it will still underperform in the real world. Communicating reapplication honestly is part of the product, not a marketing extra.
4. Heat stability
An anhydrous stick tolerates 40 degrees better than an emulsion, but it is not immune. At 45 degrees the matrix softens and the stick leans in the tube; at 50 degrees it can flow. Shipping a stick in an unventilated container in summer is the usual cause, and a simple temperature record on the container resolves it.
5. Powder dispersion
Mineral filters and pigments must be dispersed without air. A stick with visible white specks is a stick with an unmilled powder, and the defect appears only after cooling. Triple-roll milling before the wax phase is the standard fix, and the batch record should show the gap setting.
6. Fill and finish
Sticks are filled by hot pour at 70 to 85 degrees and cooled under controlled conditions. Fast cooling produces a dull, cracked surface; slow cooling produces a smooth one. The tube also shrinks away from the stick as it cools, so the fill weight must account for contraction — typically 3 to 5 percent.
7. Breakage at the base
Sticks fail at the base far more often than at the tip, because that is where the torque from the tube is applied. A stick with high powder loading needs a slightly softer matrix at the base or a shorter exposed length. Test ten sticks at 40 degrees for a week and push them against a thumb: the ones that snap at the base are the ones that will arrive broken. The fix is usually 2 to 3 percent more oil rather than more wax.
8. Where it fits
Stick formats appear in the sunscreen range; the filter question is covered in the zinc oxide entry.
Reference: Stick formulation trials and SPF application studies, 2025
