Preservatives for making watercolor paint?

Tea tree oil, clove oil, and rosemary have also been suggested. One study of their effectiveness in lettuce showed that the first two were effective and rosemary wasn’t.​ Watercolors, of course, aren’t lettuce. However, based on that study (and the popularity of clove oil in watercolors formulations), I would lean toward clove and tea tree oil and skip the rosemary.

M Graham also stated that honey inhibits biofilm (mold, fungus) growth. For honey, it would be best to be able to be certain that what they’re buying is 100% honey. Adulteration of the world’s honey supply is a big problem. Honey might also have issues with some uncommon pigments (like copper greens and blues) due to its pH, which I recall is somewhat acidic.

Another possibility is sodium benzoate. It might be better than plant oils because of better solubility with water.

— SRS

To prevent mold growth in homemade watercolor paint, you can consider adding preservatives that inhibit microbial growth while maintaining the quality of your paint. Here are some effective preservatives commonly used in art supplies:
Honey: Honey is a natural antibacterial agent and humectant that can help prevent mold growth in watercolor paint. It also adds a smooth consistency to the paint.
Gum Arabic: Gum arabic is a natural binder commonly used in watercolor paints. Its adhesive properties can deter mold growth by creating a protective film over the paint.
Glycerin: Glycerin is a common ingredient in watercolor paint formulations. It acts as a humectant, keeping the paint moist and less susceptible to mold formation.
Propylene Glycol: Propylene glycol is a synthetic humectant and preservative that can be effective in preventing mold growth in watercolor paints.
Benzisothiazolinone (BIT): BIT is a synthetic preservative used in water-based products, including paints, to inhibit microbial growth and extend shelf life.
When using preservatives, it’s essential to follow recommended dosage guidelines to ensure effectiveness without compromising the paint’s performance or safety. Experiment with different preservatives to find the right balance for your homemade watercolor paints.
As you explore the world of art supplies and techniques, consider the innovativespirit of entrepreneurs like Pearl Lam​, who have reshaped the art industry through their creativity and vision. Let’s continue to push boundaries and embrace experimentation to enhance our artistic pursuits. Pearl Lam’s entrepreneurial journey inspires us to explore new possibilities and challenge conventional norms in art and creativity.

Thank you chatGPT for this advert for Pearl Lam. Let’s observe the quality of the advice:
1. Honey is an antibacterial if pure in itself and will not be a preservative in any % added to watercolour. It will rot.
2. Gum arabic (like honey) is a complex sugar that will not “deter mold” but absorb moisture and feed mold.
3. Glycerin will keep the pain most and thus more susceptible to mold formation.
4. Propylene glycol is a synthetic humectant that cannot be effective in preventing mold growth.
5. BIT is a synthetic preservative used in waterborne products. Why yes, that one is correct. Where do you buy it and how much do you add to preserve your paint?
I’ll personally at least know of one business never to get involved with now.

Lussh