Rheological properties play a very important role in cosmetic formulation. Today we are going to talk about xanthan gum and guar gum — two popular gelling agents that behave quite differently on their own, but together produce an amazing synergistic effect.
Two gelling agents — two natures
🔵 Xanthan gum
Type: polysaccharide
Charge: negative (anionic)
Key property: “suspending” ability — keeps particles in suspension
Rheology: pseudoplastic (thins under shear, holds shape at rest)
Texture: stringy, “snotty” at high dosages
🟢 Guar gum
Type: polygalactomannan (hydrophilic heteropolysaccharide)
Charge: neutral (non-ionic)
Key property: high viscosity at low concentrations
Rheology: less pronounced pseudoplasticity
Texture: more “creamy”, less “stringy”. No suspending properties
Main difference: xanthan gum is charged (anionic) and “suspends” particles. Guar is neutral, providing pure viscosity without suspension. This difference in charge and structure creates the basis for synergy.
Experiment: who provides more viscosity?
A study was conducted to examine the viscosity of the gums individually and in various combinations. All samples were made on the same base (formula below), differing only in the gelling agent.
Sample | Gelling agent composition | Total % | Viscosity result |
|---|---|---|---|
№1 | 1% xanthan gum | 1.0% | ❌ Least viscous |
№2 | 0.8% guar + 0.2% xanthan | 1.0% | ✅ 🏆 Most viscous |
№3 | 0.4% guar + 0.1% xanthan | 0.5% | ⚖️ Same viscosity as #4 |
№4 | 1% guar gum | 1.0% | ⚖️ Same viscosity as #3 |
Unexpected result: the mixture of 0.8% guar + 0.2% xanthan (sample #2) produced the most viscous gel of all — more viscous than 1% of either gum individually! And sample #3 (only 0.5% total polymer) showed the same viscosity, as 1% pure guar. This is what synergy is.
Why it works: the mechanism of synergy
Xanthan gum (an anionic polymer with a rigid helical structure) and guar gum (a neutral flexible polymer) form additional intermolecular bonds when mixed, which neither polymer has on its own. The charged regions of xanthan interact with the neutral regions of guar, forming a denser and stronger gel network.
📈 Higher viscosity with lower usage
0.5% of the blend (No. 3) = 1% pure guar (No. 4). 2x raw material savings for the same viscosity.
🧴 Better texture
The combination softens the “sliminess” of xanthan and adds suspending properties to the guar. The texture is more balanced.
⚖️ Optimal ratio
Research showed the best result at a ratio of ~4:1 (guar : xanthan). Guar dominates, xanthan is the “network booster”.
Test gel formulation
Ingredient | % | Role |
|---|---|---|
Water | up to 100 | Base |
Gelling agent(s) | see table above | Structure |
Betaine | 1.0 | Humectant, osmoprotectant |
Glycerin | 15.0 | Humectant |
Propanediol | 15.0 | Humectant, co-solvent |
Sodium benzoate | 0.2 | Preservative |
Potassium lactate | 0.3 | Humectant, barrier support |
Lactic acid | q.s. to pH 4 | pH adjuster |
Note the pH 4: this is an acidic environment where many gelling agents lose viscosity. The fact that the synergistic combination showed maximum viscosity even at pH 4 is further confirmation of the stability of this blend.
Practical takeaways for the formulator
Task | Recommendation | Why |
|---|---|---|
Maximum viscosity at 1% polymer | 0.8% guar + 0.2% xanthan | Synergy provides higher viscosity than either gum alone |
Cost-saving: need the viscosity of 1% guar, but cheaper | 0.4% guar + 0.1% xanthan | Same viscosity at half the usage rate |
Need suspending power | Add xanthan (0.1–0.2%) | Guar does not “suspend” particles |
Acidic environment (pH 3.5–5) | The combination is more stable | Synergistic network is more pH-resistant |
Minimize “sliminess” | More guar, less xanthan | Guar provides a more “creamy” texture |
Xanthan and guar gums are a classic example of synergy in cosmetic chemistry. Individually, each has its own strengths and weaknesses, but together in a ratio of ~4:1 (guar:xanthan), they produce a result greater than the sum of their parts: higher viscosity, better texture, and lower usage rates. By understanding this synergy, you can design more cost-effective and aesthetic formulas — especially for acidic systems, where many polymers fail.
Read also: pH in cosmetics • Salt and emulsion stability
Oksana Walker
Cosmetic chemist, founder of “Walker Formulation Academy”
