Winsor & Newton Pthalo Blue Half Pan Leaving Debris? My Experience + Ask for Yours

When Your Paint Betrays You: A Disaster in Shades of Blue

There’s something wonderfully peaceful about a quiet morning with a fresh coffee, my brush in hand, working through a demo from a beloved book. That was me today — happily following along with Watercolor for Beginners by Könnemann, a little gem I picked up on sale ages ago that I keep coming back to. Everything was going smoothly. I was really in the flow and so was the water itself, doing what I wanted it to, with my paper at a 45-degree angle, watching that pigment do whatever it damn well pleased.

And then I noticed something wasn’t right.

A color I’d recently added to my set — a Winsor & Newton Pthalo Blue half pan — was leaving debris on the paper. Little bits, scattered across my wash like unwanted texture. Was I using rough paper? No.

Barring that, my first instinct was to blame the paper towel. I’d been using it throughout to blot excess water from my brush, as well as blot rogue drips from the paper so it seemed like a reasonable suspect.

But after a closer look, I realized no other color in my palette was leaving anything behind. Same paper towel. Same process. Every other pigment behaved perfectly. It was just the Pthalo Blue.

Here’s where things got a bit worse: when I touched those debris spots — just a light brush of a fingertip — they left dark pigment swipes across the surface. Normally, it's a great day when I can say I started it with blue paint staining my hands, but in this case, it's not that great. Instead, I now have mystery debris and dark drag marks to deal with once the paper dries. Not exactly the serene morning session I had in mind.

I’m still deciding how to handle those marks. There may be some careful lifting to try once everything is fully dry, but honestly? I’m not confident there’s a clean fix.

As for the half pan itself, I’m leaning toward pulling it from my set entirely and tossing it. A paint that sheds and smears isn’t a paint I can trust. I have had several half pans from Winsor & Newton and have never seen anything quite like it.

It was a frustrating little detour in what was otherwise a lovely painting morning — and a good reminder that materials don’t always behave the way we expect, even from reputable brands.

Below, you can see the work in progress and the little flecks here and there. They are quite the distraction. I am still deciding whether or not I want to try to complete it or not - maybe switching to an ultramarine instead, as it is just a fun demo.

Share Your Experience!

Has something like this ever happened to you? Maybe a pan color that started behaving strangely, left residue, or just stopped performing the way it should? I’d love to hear how you handled it — whether you found a fix, swapped the color out, or discovered some other culprit entirely. Drop your experience in the comments below!