Furnace equipments products

Coloring Forehearths

The colouring forehearth technology was developed to allow glassmakers to produce short runs of a wide range of colours without the costs of changing colour in the furnace by adding colour in the form of metal oxides in a low melting point boron based frit. The colour forehearth technology is very flexible allowing the full range of production in a wide range of colours including container, table ware and cosmetic containers. Glass Service has developed colouring forehearths in various sizes and lengths, each designed for the specific pull, colour range and production.

Glass Service design and supply the forehearth colouring technology as well as all of the necessary production equipment:



The systems are of strong reliable construction, designed for continuous operation. The main concepts of our colouring forehearths are: simplicity, flexibility and reliability. The automatic frit dosing device and the stirrer machine can be easily adapted to a wide range of pull rates and require low maintenance even when operating under heavy working conditions.

Glass Service has designed and provided coloring forehearths to many customers in Italy, France, Turkey, Russia, China, Poland, Morocco and Spain.

Coloring Forehearth


Glass heating zone and colouring frit addition


Stirring zone

One stirrer mechanism is installed before the spout so that during colour changes eliminates any small colour variations and reduce colour change time



The colouring foreheart technology has a number of critical point for successfull operation

Issue Solution
Accurate dosing of the frit
A good dosing device technology is required
Constant chemical composition of the frit
First quality frit
Constant redox atmosphere
High quality combustion system and FH design is required
Homogenous mixing
Good mixing technology
Good mixing technology
Rapid colour change
The correct FH design is required to minimize the colour change time. The stirrer mechanism installed before the spout eliminates any small colour variations and reduce colour change time.
Long life of refractories
The frit contains a high level of boron, during melting the boron vapours corrode the standard refractory superstructure. A special design of refractory quality increase the FH life.

Automatic Frit Dosing Device
With Air Cooling Package

The dosing system controlled by a PLC

The feeding tubes are each provided with 2 thermocouples

Temperature of the feeding tubes controlled by a UDC

Easy access to the dosing system for the operator

Easy maintenance

Strong steel structure above the forehearth

Glass Service develop a new concept of frit dosing with the frit dosing unit install at low level and the dosed frit transport on the foreheart by pneumatic system.

A main hopper contain the frit (see (1) into the sketch below). This hopper must be periodical fed by the operators. A dedicated sensor located on the base of the hopper generates an alarm when the hopper must be refilled. The dosing system delivers the dosed amount of frit to the feeding transport system. To regulate the frit flow, the PLC with color touch screen manage the automatic dosing system (2), adjusts automatically the speed of the conveyor belt.

This transporting system is formed by a high pressure air blower (3) which blows the air inside a stainless steel pipeline up to a centrifugal dust separator (4). The frit is constantly sucked through one injector inside the stainless steel pipeline up to the centrifugal dust separator. Once arrived at the separator the frit falls to the feeding tubes. The feeding tubes are installed into the forehearth superstructure and provided of thermocouple for temperature control (by an single loop controller) and cooling air (5).

This layout allows the dosing machine to be located on ground into a position where the operating temperature of the electronic devices must be kept under 40÷45°C. Besides this the described position allows the operator to have easy access to the system, to provide better maintenance to the equipment and to put the coloring frit into the main feeding hopper without problems. The frit insertion tubes are to be positioned onthe top of the forehearth superstructure.

Technical Features

Dosing max flow
140 kg/h
Dosing min flow
5 kg/h
Main hopper (A) standard volume
600 litres
Main transfer device
Electromagnetic vibrating channel
Dosing transfer device
Special rubber belt drive by brushless motor
Electronic strain cage high precision
Electronic control
Automatic by touch screen PLC

Stirrer Machine

The stirrer machine is used for glass and colour homogenization. (For more details about stirrer machines see relative documentation).

Vertical height
2.275 mm – customizable
Vertical stroke of stirring mechanism
950 mm – customizable
Distance from the centre of the forehearth to the stirrer support
1 - 5
N° of rotors
120 kg
Max. weight of the stirrer screw
1,3 – 13 rev / min
Stirrer speed
0.75 kW
Installed power
screw or blade
Stirrer type
Torque control clutch to avoid stirrer torque braking

Control Board

The design of Glass Service control board features the following main characteristics:

The touch screen interface can manage all of the required information for the colouring technology, managing the dosing, alarms, trends, settings, etc.

The default alarms are:


The PLC software allows the operator to change the menu language, calibrate the scale, view the history alarms, set the dosing rate, view the flow trend and manage all of the parameters in a single menu. Additional information can be incorporated on request.

Main page

Flow trend