Color Stability in Layered Anhydrous Stick

When creating an anhydrous stick formulation with oil-soluble colors and layering different colored formulas, encountering issues like color phasing (sedimentation or separation) and color bleeding/mixing between layers is common. This problem often arises from the nature of the colors used and the structure of the anhydrous stick base.

Oil-soluble dyes tend to migrate easily within an oil or fat base, especially if the formula is relatively soft. Pouring layers before the previous layer has fully solidified, or if the overall formula is too soft, can cause color from one layer to move into and mix with another.

Here are some approaches to address this issue:

• Adjust the Product Structure: Increase the amount of hardening agents (such as Waxes, Solid fats) to make the product structure stronger and more stable. A stronger structure helps reduce the migration of color between layers.
• Consider Using Pigments Instead of Dyes: Pigments are solid particles that do not dissolve in oil or other solvents. Using pigments instead of oil-soluble dyes may help reduce color bleeding issues, as pigments are dispersed within the formula but do not dissolve and move around like dyes. However, using pigments requires careful consideration of color dispersion to ensure uniformity.
• Control Temperature and Pouring Time for Each Layer: Ensure that each layer poured has completely cooled and solidified before pouring the next layer. Pouring a new layer while the previous one is still warm or soft will increase the chance of color bleeding or mixing.
• Select Appropriate Waxes or Polymers: Certain hardening agents may create structures that better trap colors or form barriers that help prevent color migration.

In summary, resolving color phasing and bleeding issues in layered anhydrous stick formulas typically involves strengthening the product's structure and potentially considering a change from dyes to pigments.