When do you use masking fluid, and when gouache? Both what stage of the painting and in which case does one or the other make sense?

You may know how much I love negative painting, so I tend to use masking fluid and gouache very rarely. However for this painting, I knew there was little hope of negative painting all those sections between the beams without having mismatched color on one side or another of the white areas!

Tutorial: When to use masking fluid vs white gouache in watercolor

Watch the video below and scroll to the end to leave comments or questions — or click HERE to watch it on YouTube and leave comments over there. I read both dutifully!


A lighter background or multi-valued one allows all the fussy lines to sometimes be white, sometimes black or grey (watered down black).


The wavy water was looking too fussy, but a wash of dark color over the entire bottom de-emphasized the white – and made the water crave less attention.

Fussy details

Let the little bits be just that – bits of color, line, and shape. Trying to paint every item in detail can cause the painting to get just toooo fussy.


The beams are the best for using masking fluide – though you can see they’re very imperfect! It’s hard to get the gooey fluid down very smoothly.


The words on the boat would have been nigh impossible to achieve with masking fluid at this size, so gouache was fine for this area. Allow some of the gouache lines like the door glass become drybrush so it matches the watercolor.

See it as a whole

Always take steps back from your work and ask yourself where your eye is drawn to. Focal points are where whitest whites and darkest darks touch. Too many of them? Try washing some of them with a pale grey.

Negative painting is still my love!

Leaving the white while painting is always my preference, except for subjects like the boat today. It’s always more coherent with the artist’s linear style; so there aren’t areas that stand out like a sore thumb. It’s always worth practicing negative painting so you can avoid all the other products too!


  1. Gab

    You are so talented Sandy – I really loving watching and listening to you as you create and explain why you make certain choices

  2. Helen Finlay

    Wonderful video. Love your easy to follow explanation Sandy. A stunning painting. Thanks so much.

  3. Paula Corcoran

    Loved your explanation about the masking fluid and gouache. Have you ever tried using a ruling pen for applying thin lines of masking fluid?

    • Sandy

      I’ve found them to be soooo difficult to use, but others swear by them.

  4. Terry Blanchard

    What a beautiful painting! I’m amazed at how you made a painting of a boat look so majestic and beautiful! It feels like you are there in person looking at the real thing. You can feel the atmosphere there! Well done!

    • Sandy Allnock

      Thank you!


Submit a Comment

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.