Glass Quality

Reduce seed and blister

One of the most striking effects of using Calumite is the virtual elimination of seed and blister caused by excess residual sulphate, due to the interaction of Calumite with the sodium sulphate in the batch.

On average a 50% reduction in seed count is observed. Two examples of a reduction in seed count on Calumite implementation are shown below.

Green Container Furnace

Flint Container Furnace

Reduced batch stones

The combination of faster melting and lower temperature dissolution of silica grains when using Calumite can result in a reduction in batch stones without the need to increase furnace temperatures. The graph below shows how the implementation of Calumite in a float furnace led to the virtual elimination of unmelted silica defects.

View graph

Improve redox control and colour stabilisation

Calumite is a weak reducing agent when compared to reducing agents such as carbon. As a result, comparatively large amounts of Calumite are added to the recipe, resulting in more even distribution within the batch. In addition, the larger particle size of Calumite compared to other reducing agents ensures the material is available to react over a longer period of time, improving the redox control within the furnace.

Calumite is particularly valuable in the production of amber glasses, or glasses with an amber component to their colour, such as dead leaf green or UVA green due to the nature of the amber chromophore that produces the colour in these glasses.