Test Mixing for the Best Blues: Ultramarine Blue vs Phthalo Blue

I recently added a tube of phthalo blue paint to my palette, and I’m sharing the results of my experiments to test out ultramarine blue vs phthalo blue. The differences are surprising!

Limited Beginner’s Palette of Oil Paints

When I began oil painting a little over a year ago, I followed Miss Mustard Seed’s recommendations for a limited impressionistic landscape palette.

I purchased ultramarine blue, yellow ochre, burnt sienna, cadmium yellow pale, and titanium white. Just 5 colours. And that limited palette has worked well for the landscape paintings I’ve been doing.

The only other colour I bought was Napthol red so that I could add red to lighthouses, and mix purple and orange occasionally for flowers.

Recently however, I set out to do a study of a couple of paintings, and I found myself limited by the blues that I could mix for the skies and the water. Mine were all so muddy and grey and I couldn’t mix the turquoise-y water and sky colours in the original painting. If I added yellow to ultramarine blue, I just ended up with green.

That left me feeling a bit frustrated and that my limited palette was, in fact, limiting. So I set out to understand how I could get those brighter, turquoise-y blues. If you don’t know it about me already – I love those blue-greens!

If you’re interested in learning to oil paint on a budget, check out my post about the Top 5 Requirements for Setting Up a Small Space Home Art Studio.

And check out my 52 in ’22 Art Challenge!

Ultramarine Blue vs Phthalo Blue

I learned that there are several blue paints that will yield a more turquoise colour. The most common pigment is phthalo blue.

Ultramarine blue tends toward having a violet undertone, and so it is a warmer blue. Phthalo blue tends toward a more green undertone, and is therefore a cooler blue. It’s this green undertone that can help produce the blue-green shades.

Phthalo blue pigments are also considered to be stronger than ultramarine blue pigments. This means that you will need to add more white paint to tint it. For this reason, some people choose other blue paints instead of phthalo blue.

How Do You Say Phthalo Blue?

When I went to the art store to buy the tube of phthalo blue, I had to ask for someone to open the locked artist grade paint cabinet. I was actually embarrassed about mispronouncing the name of the paint, so I just said, “This one,” and selected it myself.

Then I went down an Internet rabbit hole trying to find the answer to this question. And I found so many different answers that I’m really not sure that there is a consensus on this. I think it is most commonly pronounced like either “thay-lo blue” or “thal-o blue”, where the ‘Ph” is silent. However, one pronunciation was “salo”, which seems odd to me.

I did note from old videos that Bob Ross says “thay-lo”, so that’s how I’m going to say it. But mostly I’m going to try to avoid saying it aloud!

Testing Out the Difference Between Ultramarine Blue and Phthalo Blue

When I was learning to oil paint, one of the first free classes I took was from Miss Mustard Seed about learning to make colour charts. It was very valuable to start experimenting with oils and learning to mix colours in this way. I tested out all two-colour combinations with my limited palette before diving into paintings.

I think that we all have a basic concept of colour mixing from grade school. We know that red and orange make yellow, and blue and yellow make green, and so on. We maybe tried it out with cheap tempera paint pucks at school, but everything yielded a brown combination.

And so, for me, it was exciting to practice mixing paints in a methodical way, and to see the huge range of colours that could be achieved from mixing with one tube of paint. It surprised me how responsive the colour change could be by adding just the tiniest amount of another colour.

I decided that I wanted to do a colour chart with phthalo blue, cadmium yellow pale, and titanium white, just as I had done with ultramarine blue. That would give me a good comparison to see the difference in the blue-greens and greens that I could make with each blue.

Different Levels – Different Pigments

Now, I need to note here that there are different pigments in different levels of oil paints. Oil paints come in two levels or grades – student grade and artist grade.

Student grade oil paints are less expensive, because they contain less pigments per tube, and less expensive pigments.

Artist grade oil paints are more expensive because they contain a higher quantity of pigments and more expensive pigments. They also come in Series 1 – 5 with 1 using cheaper pigments and 5 using more expensive pigments.

I chose student grade oil paints when I began since I didn’t know if I would like oil painting. As I’ve discovered that I enjoy it, I’ve slowly been upgrading my oil paints to artist-grade. Though I haven’t opened any of them up yet and so I can’t compare between student and artist grade.

The original colour chart using ultramarine blue, cadmium yellow pale, and titanium white all used student grade, series 1 paint. The phthalo blue that I bought is artist grade, series 2 paint. Therefore, the pigments are stronger, which I think explains why it was more difficult to get the colours at the bottom of my colour chart to be as pale.

If you want to make your phthalo blue less intense (so you don’t need to add so much white paint to lighten it), you could use a student grade phthalo blue so it has less pigments to begin with.

Colour Chart – Ultramarine Blue vs Phthalo Blue

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To make colour charts similar to this one, you can follow along using Miss Mustard Seed’s free online class.

I like using my 9 x 12″ Canson oil and acrylic pad pages for my colour charts, as they’re the perfect size for 5 rows of 7 squares and a margin on either side. To tape the squares, I use Scotch Green Painter’s tape, and 1/4 inch masking tape.

I was so excited that even after completing just the first column that the blues were entirely different. And by the middle of the chart, I was getting my favourite shades of turquoise, teal and blue-green. This was opening up all new possibilities for my paintings!

When comparing the colour charts of ultramarine blue vs phthalo blue, there is quite a difference. You can see below that ultramarine blue mixed with cadmium yellow pale yields warmer, muddier colours, and lots of greens from olive, moss, and sort of a pea soup colour. Phthalo blue mixed with cadmium yellow pale yields cooler, brighter colours, and lots of teal, turquoise, and brighter sky blues. I was honestly surprised by how different the results were.

I love making colour charts – I find it very relaxing and almost meditative. It’s a very methodical and orderly task, yet the colours that are revealed are always surprising and creatively inspiring to me. The most fun part is pulling back the tape to see the colourful little squares neatly revealed. (I did get a bit more bleeding under my tape this time though, as I think I applied the paint differently.)

2nd Attempt at a Painting with Phthalo Blue

After doing the colour chart, I was excited to make another attempt at my recent painting. I was hoping that I’d now be able to mix colours found in the original painting. Though I had been happy with my first version, I wanted to see what phthalo blue could bring to it. (As mentioned in my previous post, the original was found from the @CanadianPaintings twitter account, and is titled “The Agate Hunters, Martinique Beach, N.S.” by Bruce LeDaine.)

As it turns out, it was so much easier to make the turquoise-y colours for the sky and water. In fact, I already had them mixed from making my colour chart.

I found it difficult to mix exactly the same colours and copy other things that I did the first time. Therefore, I ended up changing several things about the foreground in the picture, as well as the sky.

While I still like the first painting, I love this second one much more. The colour of the sand is more realistic, and the grasses turned out better. But most of all, I love the brighter turquoise that I was finally able to achieve. I don’t often like doing the same project more than once in a row. However, I’m learning that there can be great value in making a second attempt.

Ultramarine Blue, Phthalo Blue, and Beyond

Going forward, I’m so excited to experiment more with phthalo blue. Ultramarine blue will still be an integral colour on my palette for mixing darks and other greens. But now I also have another useful blue to add to my palette.

As well, I’m definitely going to try making a colour chart with each new tube of paint that I purchase to get a feel for what it can do, and how it varies from the other colours in my palette.

I want to hear from you. What experience do you have with mixing colours? Do you remember doing it in school? Have you ever mixed custom home decor paint to get just the right shade?

As well, which of my two painting versions do you prefer? The original with just ultramarine blue, or the second attempt with the phthalo blue to make turquoise?

Let me know in the comments below.

All the best,

Danielle