As an artist, exploring colour might be one of my most favourite things to do. While a creative process, there are ultimately a lot of technical aspects to consider; primarily, the science of mixing pigments.
When working with Jesmonite, the official pigments I have access to are red, blue, green and yellow. I can also mix with black and white and some ancillary colours that include coade, red oxide, yellow oxide and terracotta.
For the purposes of this demonstration, I'm only going to use the colours I already have in stock: red, blue, yellow and terracotta.
Black and white are not colours, though they are very useful for changing the shade of the colour you're mixing, ie. Adding more black creates a darker shade and adding more white will produce a lighter shade.
Adding more coloured pigment will increase the saturation of the colour, mixing coloured pigments will alter the hue and adding more black/white will adjust the shade.
As an aside, there are unofficial Jesmonite pigments you can use, including powders, paints, inks and more. The Jesmonite pigments are reliable and compatible with Jesmonite whereas other branded pigments may not be able to achieve the precise colour you desire or mix as evenly throughout the product.
Why does adding brown create richer, earthier colours?
If we highlight brown on the colour wheel, it sits within the warmer side of the wheel. The families of reds, oranges and yellows will result in a different warmth of brown.
Therefore, if you're going to mix brown with a primary colour, you're going to introduce warmer tones. This is why the colours feel richer and, well... warmer.
The Process
For this demonstration, I am simply mixing 1:1 red, blue or yellow with terracotta.
You can achieve vastly different colours be adjusting that mixing ratio, but I wanted to show what happens when you add equal parts red, blue or yellow with terracotta.
Firstly, I am adding 1% red, blue or yellow to demonstrate the unaltered colour. Then I'm adding 1% red, blue or yellow with 1% terracotta to demonstrate the effects of adding terracotta to a primary colour.
Note, Jesmonite recommends a maximum mix of 2% pigment added to the material; any higher than this could risk the structural integrity of your casts.
Mixing red with terracotta
Lets start with an easy one. What happens when you add a warm colour to an already warm colour? That's right, it gets even warmer to create a deeper shade of red.
1% pure red Jesmonite pigment creates a vibrant colour that still errs on the side of pink in my opinion. When mixed with an additional 1% terracotta it creates a rich mauve.
Playing with these ratios you can achieve a wide range of red-brown hues including, but not limited to: blush, salmon, mauve, maroon, vermillion, mahogany etc.
Mixing blue with terracotta
In contrast to red, blue is considered a cool hue. Therefore, mixing blue with terracotta almost neutralises any coolness/warmness.
Something I've done in the past is mix tiny amounts of blue and terracotta pigment to create a lovely silvery grey.
You can see from the demonstration that 1% pure blue Jesmonite pigment creates a fantastically vivid blue. When mixed with an additional 1% terracotta it moves closer to grey. I would call this a steel blue.
Other ratios of blue with terracotta could create a range of colours including, but not limited to: pigeon, steel, taupe, umber etc.
Mixing yellow with terracotta
My relationship with yellow is tricky. I like a very particular vibrant yellow and I tend to avoid shades that move more towards gold/amber. I was certain I wasn't going to like a yellow and terracotta mix, but, as usual, I was proven wrong!
1% pure yellow Jesmonite pigment creates a wonderfully bright yellow. When mixed with an additional 1% terracotta it steps more towards a honey or a mustard.
Yellow can be a complicated colour to work with, but by adding terracotta you can achieve a range of colours including, but not limited to: camel, mustard, gold, sand, fawn, biscuit etc.
The Findings
Adding terracotta to red, blue and yellow pigments allows for a richer range of colours to be achieved. While this demonstration showcases a 1:1 mix, it highlights that there are endless possibilities to be achieved with how colours can be mixed.
I would highly recommend trying this experiment yourself. One of the best ways to understand how colour works is to actually work with it.
Having a richer understanding of how to make colours can really inform a lot of your stylistic choices, especially when it comes to pairing colours and shades.