According to the provided reference, metallic lustres, including those potentially containing copper, have a dark brown colour in their colloidal form.
The Appearance of Metallic Lustres
Metallic lustres are special preparations, often in a colloidal form, used to create decorative metallic effects on surfaces like ceramics or glass. The reference explicitly describes the appearance of these lustres before they are typically fired onto a substrate.
Key Characteristics from the Reference:
- Colloidal Form: Liquid gold and metallic lustres exist as colloids.
- Colour: In this colloidal state, they have a dark brown colour.
- Composition: They contain dissolved metals as a main component.
The reference states: "Liquid gold and metallic lustres have a colloidal form and have a dark brown colour; they contain dissolved metals as a main component." This indicates that the liquid material you might apply, which contains dissolved metals like copper for a copper luster effect after firing, is dark brown in colour.
It's important to note that this description pertains to the preparation itself (the liquid luster material), not necessarily the final fired colour, which can vary widely depending on the specific metal, concentration, firing temperature, and atmosphere. However, based solely on the provided reference, the colour of the luster material containing dissolved metals like copper, in its colloidal form, is dark brown.
