Colouring agents, which insert the colouring product, are used for the colouring process. Copper, chrome, nickel, selenium, cobalt and other elements enable a wide range of colours. Various combinations of these elements extend the palette of colours even further.

In order to feed these colouring agents, a specially designed feeding unit needs to be installed. This feeding unit consists of several components:

• A small batch hopper is used to store the colouring agents
• A dosing chute feeds the adjustable quantity of agents from the hopper to a weighing pan
• A special weighing socket weighs the exact quantity of colouring agent
• A pneumatic deduster reduces the fine particles from the agent to prevent refractory corrosion
• Charging funnels with distributor for single, double or triple charge, feed the agents through the roof of the forehearth onto the glass surface