Tween vs Span: How to Choose and Blend Emulsifiers
<strong>Span</strong> grades are sorbitan fatty acid esters (low-to-mid HLB). <strong>Tween</strong> grades are polysorbates — ethoxylated sorbitan esters with high HLB. Formulators rarely choose one in isolation: they blend Tween and Span to match the required HLB of the oil phase for stable O/W or W/O emulsions. Venus Ethoxyethers manufactures polysorbates and sorbitan ester chemistries for cosmetic, pharma, food, and industrial use.
Quick definition
- Span (sorbitan esters): Non-ethoxylated; lipophilic; HLB roughly 1.8–8.6 depending on grade
- Tween (polysorbates): ~20 EO moles on sorbitan esters; hydrophilic; HLB roughly 14.9–16.7
Deep dives: sorbitan esters guide and polysorbate 20/40/60/80 comparison. HLB math: HLB scale guide.
Grade map
| Fatty acid | Span | Tween | Notes |
|---|---|---|---|
| Lauric | Span 20 | Tween 20 | Higher HLB pair; solubilization |
| Palmitic | Span 40 | Tween 40 | Mid chain; food/ointments |
| Stearic | Span 60 | Tween 60 | Creams, bakery body |
| Oleic | Span 80 | Tween 80 | Liquid pair; pharma/food |
When to lead with Tween
Choose polysorbates when you need O/W emulsification, fragrance/oil solubilization, or aqueous pharmaceutical systems. Tween 20 for light oils and washes; Tween 80 for biologics, injectables support, and many food emulsions; Tween 60 when waxy body helps creams.
When to lead with Span
Choose sorbitan esters for W/O emulsions, pigment wetting in oil phases, and as co-emulsifiers that pull system HLB down. Span 80 is common in oil-rich industrial and cosmetic W/O systems; Span 60 builds structure in creams.
Worked HLB blend
Target required HLB ≈ 11 for a mineral-oil cream oil phase:
- 70% Tween 60 (HLB ~14.9) + 30% Span 60 (HLB ~4.7) → blend HLB ≈ 11.8
- Total emulsifier 3–5% on formula; adjust ratio if heat-age separation appears
- Match fatty acid family where possible (stearate with stearate) for cleaner interfaces
Decision checklist
- Emulsion type O/W or W/O?
- Required HLB of oil blend?
- Need liquid process or waxy body?
- Regulatory lane (cosmetic / food / pharma)?
- Blend Tween + Span rather than forcing a single grade
Contact Venus for polysorbate and sorbitan ester sampling. Related: what is an emulsifier, emulsifiers hub.