青花釉里红
Combined underglaze system using both cobalt blue and copper red pigments applied simultaneously to porcelain body before glazing and high-temperature firing. Technically complex requiring precise atmospheric control for stable dual-pigment results.
Technical Structure
This system layers two underglaze pigments — cobalt blue and copper red — onto the same unfired body before a single high-temperature firing. Cobalt and copper respond to different conditions inside the kiln: cobalt is comparatively forgiving, but copper red requires a narrow band of reduction atmosphere to hold its colour and will turn grey, brown, or disappear entirely if the kiln strays outside that range. Firing both pigments together in one pass means there is no opportunity to adjust one without risking the other.
The combined technique appears in Yuan-dynasty production and reappears at points across the Ming and Qing when kilns had the technical control to justify it. Because the copper red is so sensitive to firing conditions, pieces where both colours emerge clean and stable represent the technique working as intended rather than as the more common alternative outcome.
Look for the copper red holding a genuine red rather than sliding toward brown or grey, and for the blue remaining stable alongside it — evidence that the kiln atmosphere was held within a narrow window for the full firing.