Shampoo Base: Dilution, Fragrance Effects & Troubleshooting
Working with a shampoo base is straightforward, but viscosity can change depending on how you customise it. This guide explains how to thin a thick shampoo base, what to do if your fragrance makes it too thin, and how to correct over-thickening so your final product stays easy to use and easy to pump.
Why Shampoo Base Thickness Varies
Shampoo bases contain surfactants, conditioning agents, and stabilisers.
When you add water, essential oils, or fragrance oils, these ingredients interact in ways that may temporarily or permanently shift viscosity.
This is normal and easy to manage once you know what to look for.
How to Thin a Thick Shampoo Base
If your base is too thick to pump or pour, dilution is the simplest method.
Recommended Dilution Rate
Use 3–10% distilled water, depending on how fluid you want the final shampoo to be.
Steps:
- Add 3% distilled water
- Stir slowly to avoid foaming
- Let it rest 12–24 hours
- If still too thick, increase to a maximum of 10%
This does not impact cleansing ability or foam when kept within the recommended range.
How Fragrance and Essential Oils Change Viscosity
The most common cause of unexpected thickening or thinning is actually the fragrance or essential oil added.
Fragrance oils that thicken:
- Vanilla
- Cinnamon and clove blends
- Some florals
- “Warm” and “gourmand” blends
Fragrance oils that thin:
- Citrus oils
- Spearmint and peppermint
- Eucalyptus
- Light, top-note blends
These changes occur due to the surfactant/fragrance interaction, not due to a fault in the base.
If Your Shampoo Becomes Too Thin
This can be corrected using a simple salt-thickening method.
Salt Thickening Method
- Dissolve 1 tsp table salt in 100mL warm distilled water
- Add 1–2mL of this solution into the shampoo
- Stir gently
- Wait several hours for the final thickness to develop
Salt adjusts viscosity in most surfactant systems and gives you back control when a fragrance thins the base too much.
If Your Shampoo Becomes Too Thick
Thickening is usually caused by floral or spicy scent oils.
To fix it:
- Add distilled water in small increments (3–5%)
- Stir slowly
- Allow at least 12–24 hours for the shampoo to settle
Avoid adding more than 10% total water unless you are comfortable adjusting preservatives.
How Much Fragrance or Essential Oil to Use
For best results:
- 0.5%–1% total fragrance load is ideal
- Essential oils should not be added in carrier oils
- Allow the shampoo to stabilise for 12–24 hours before making further changes
This prevents over-correction and keeps the base balanced.
Final Tips
- Mix slowly to minimise bubbles
- Always record your percentages for easy repeat batches
- Allow resting time — viscosity often changes overnight
- Test small batches before scaling up