The two terms are sometimes used interchangeably, but they are distinct. High time to list those differences.
What are oxides?
There are many different types of oxides, which are also used for different purposes. In each case, they consist of only two elements: oxygen, and another element such as silicon, calcium, lead, zinc, iron …
Some oxides are melters: they cause the clay particles to begin to melt at a lower temperature. Other oxides, in turn, are used as glass formers: they increase glass formation during firing.
In addition to these two functions, oxides can also be used to add colour. They are added to glazes, underglazes, clay sludge, or to the clay itself.
What are pigments?
You could say that pigments are simply a more ‘processed’ version of oxides. They are made by heating a combination of different oxides so that they fuse together, and then grinding them into a powder.
This is more or less the same process as is used to make frittes. And the use of pigments provides many benefits:
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Pigments produce predictable, reproducable colours.
The colour of the unfired ceramic pigment is a lot closer to the colour your piece will be when it comes out of the kiln. In many cases, the colour is also a lot brighter than that of oxides. -
Pigments are less toxic and less soluble.
Because pigments have been fired before, some of the bad properties of the raw materials have already disappeared. For example, compounds of lead or barium are already fused with glass formers and thus encapsulated so that they are no longer harmful. Caution: do always read the label to know if a pigment is suitable for tableware. -
With pigments, you will find a wider variety of colours.
Because pigments are made by combining different oxides, the available colour spectrum is much larger. Some colours that are very difficult to mix yourself with oxides, you can just find ready-made as pigment.
Just like that, all clarified. So for more colour in your pieces, you can rely on both oxides and pigments. While oxides additionally have other functions up their sleeve, with pigments you have a wider choice of colours. And you are also more certain that the colour you choose will look the same on your fired piece.
