Colour flexibility when you need it. 

Colourant Forehearths

Colourant forehearths allow different colours of glass to be manufactured in the forehearth without changing the glass colour in the furnace. This is done by the addition of frit close to the forehearth entry, and a series of stirrer positions along the forehearth to mix the melted frit into the parent glass.

The PSR colourant forehearth is an excellent way to increase the flexibility of production and add value to the product.

Applications include the manufacture of cosmetic containers and tableware, as well as beer, spirits, and beverage bottles where changing colour in the forehearth is preferred to changing colour in the furnace.

Key Features

  • Increases production flexibility and adds value to the product.
  • Short production runs enabled rather than changing colour in furnace.
  • Makes production scheduling easier.
  • All colours can be manufactured except amber. A similar colour known as bronze is possible.
  • Amber glass melted in the furnace can be made darker.
  • Consists of frit addition section where frit added and melted followed by stirrer section where melted frit is stirred into the parent glass.
  • Number, size and specification of stirrer banks is specified by PSR to meet the required output of the forehearth.
  • Extra residence time is required in the forehearth to enable the frit to be melted and the coloured glass to reach the desired gob temperature.
  • Stirrer systems manufactured in-house to PSR standard stirrer design.


The PSR colourant forehearth consists of storage and weigh scale hoppers that feed a metered amount of frit into the frit addition point close to the forehearth entry. Sufficient forehearth length is then required before entry to the stirring section in order that the frit can be melted into the parent glass. Temperatures in the range 1260-1300°C are required at the frit addition point. This temperature must be maintained through to the first bank of stirrers.

The number of stirrer banks is determined by the required tonnage and glass colour to be manufactured and the number of stirrers per bank is a function of the width of the forehearth. The configuration of stirrers on each bank will be configured to provide optimum mixing of the frit as the glass flows through the banks of stirrers. Each bank of stirrers is operated by a separate control panel allow the speed of rotation of each bank of stirrers to be controlled to provide the optimum results.

After the glass has left the last bank of stirrers sufficient forehearth length and cooling capacity must be available for cooling the glass from its mixing temperature to the required gob temperature. The System 5oo forehearth cooling system provides the high cooling rates required whilst controlling the glass temperature homogeneity.

Glass contact materials for the frit addition and mixing section channel blocks are typically supplied in a fused cast AZS material. With excellent corrosion resistance to the volatile materials present in the forehearth atmosphere from melting of the frit, PSR-333 provides the ideal superstructure refractory material for colourant forehearths.

The MR-5000 combustion system provides the high firing rates required in the frit addition and mixing sections whilst maintaining close temperature control. The ceramic burners supplied with our combustion systems have been proven not to block up even in the volatile atmosphere inside a colourant forehearth.

Almost all colours can be manufactured in a colourant forehearth with the exception of amber where only a bronze colour is possible. Coloured glass melted in the furnace, including amber glass, can also be made darker in a colourant forehearth.