What makes watercolour such a challenging medium is that you can’t cover up mistakes as you can in other painting mediums. As watercolour is translucent and requires that you work from lightest to darkest values, it is extremely important to preserve your whites. In some cases, you can just paint around the shapes but when it comes to more complex or very small areas it becomes nearly impossible. This is where the masking fluid comes in. Essentially masking fluid is liquid latex which you can paint onto areas you want to preserve and protect from paint – and once it’s dry it can be peeled off, revealing the untouched whites below. It’s a bit like magic!