Possible spoiling oil-based mixture?

Benz3neBenz3ne Member
edited February 12 in Advanced Questions
Background: [the company] makes a heavily-pigmented, oil-based mixture that is not typically sold in shops but directly to end user(s).
The mixture is predominantly vegetable oil(s), natural waxes (e.g. beeswax/rice bran wax/other), mineral pigments (approx 1/3 of mixture), some emulsifiers to aid wash off (polysorbate 80 and oleyl alcohol) and methylparaben as preservative.

Issue: Have noticed 'leaching' of something oily from one of the colours of a batch that has been in stock for circa 18mo. To me there is a slightly stronger, waxy/oily odour than normal but not overwhelming or particularly rancid. Under the 'leached' oil-stuffs the top layer is now spongy and not spreadable. The top layer is not combinable with the leached oil-stuffs either at room temp or under heat (as per manufacturing of product). The leached oil-stuffs is stringy, tacky, sticky unlike any of the raw materials or combinations thereof.

Question: Am I on the right lines that it is spoiling in this one instance? There are other colours that have not exhibited this. All colours feature mineral pigments - the one differential is that the colour with issue features a FCF lake pigment also, in small quantities. I have used this in the same base but with additional pigments without issue. We have an accelerated stability PAO of 6mo but the product has not been in our repertoire for particularly long (circa 24mo).

I have attempted recombination/reconstitution without success (remains caky/lumpy with basic stirring under heat, unlike unspoiled product which melts quickly and homogeneously). Have also tried retaining at temperature (35°C+ for circa 2 hours) to try and accelerate leaching. Removing leached oil-stuffs and holding at temperature shows no leaching/sweating of product. Correct consistency product shows light leaching/sweating at temperature. Removal of top skin of spoiled product shows light leaching/sweating consistent with unspoiled product.
I'm inclined to think it's not a stability (of mixture) issue given that other colours have remained correct in storage.


  • PhilGeisPhilGeis Member, Professional formulator
    edited February 13
    Methyl paraben alone is a pretty weak preservative system.  Have you conducted any micro testing - challenge or content?

  • PhilGeis said:
    Methyl paraben alone is a pretty weak preservative system.  Have you conducted any micro testing - challenge or content?

    Thanks Phil - the issue I'm facing is that the product is dispensed hot (45+°C) so need something reasonably heat-stable. I'd gladly look to replace it if I could find a suitable replacement.
    We've had challenge testing done on similar products with the same preservative system previously and have seen no issues otherwise, but I'll readdress with this seeing as it's thrown an issue.
    I think it could be an incorporation issue during processing. That the mixture is not homogeneous so some portions are with more methylparaben than others. Not ideal at all, so going back to the drawing board.
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