How does mold develop in your watercolor palette

One of my students brought in the photo below of mold or fungus growing over some of the watercolor paints in his palette.

Figure 1: Mold or fungus on growing on watercolor paint in palette

I have heard of this for many years though I have never experienced it myself or met someone personally who has experienced it so I thought I would take this opportunity to record it.

Mold is basically another name for a type of fungus. These mold spores are everywhere; however they need the right environment within which to grow. Firstly they need food (in this case this type seems to like watercolor paint)!  Secondly they require water, specifically high humidity of around 70%, they also like high temperatures around the mid 70’s Fahrenheit – they also like darkness and stagnant air. So you can see that these could very well be the conditions in an enclosed wet watercolor palette!

I think the reason I have not had mold develop on my watercolor palette is because I generally let my palette dry out and prefer to paint with watercolors that are drier rather than straight from the tube. I mainly use Winsor and Newton artist’s quality tube paints and find that they re-liquefy very easily even after they dry out – at least for the palette of watercolors that I use.

How to protect against mold in your palette

If you find mold developing in your palette I suggest you let the surface moisture dry before you put the lid back on it. Then just before you start your next painting you can lightly spray water over each of your paint wells to make them easily workable. With the Windsor and Newton paints I use I find I don’t even need to give them a spray.

If you have mold that has developed then just wash it off with water before you start painting. Keep it off your fingers as some varieties are toxic to humans!

Hopefully you will never have mold on the watercolors in your palette but if you do maybe the above can throw a little light on the subject.