A submerged combustion melter includes a floor, a roof, and a sidewall structure connecting the floor and roof defining an internal space. A first portion of the internal space defines a melting zone, and a second portion defines a fining zone immediately downstream of the melting zone. One or more combustion burners in either the floor, roof, the sidewall structure, or any combination of these, are configured to emit the combustion gases from a position under a level of, and positioned to transfer heat to and produce, a turbulent molten mass of glass containing bubbles in the melting zone. The fining zone is devoid of combustion burners or other apparatus or components that would increase turbulence above that in the melting zone. The melter may include a treating zone that stabilizes or destabilizes bubbles and/or foam. Processes of using the melters are a feature of the disclosure.

A glass has a coefficient of thermal expansion in a temperature range from 20? C. to 300? C. of 4.5 ppm/K or less, and a T4 temperature, defined as the temperature at which the glass has a viscosity of 10.sup.4 dPa*s, at 1500? C. or more, and having a reboil propensity score of less than 10 measured in a reboil propensity test. The reboil propensity score is determined as a number of bubbles per glass rod formed from the glass after the reboil propensity test.

A glass has a coefficient of thermal expansion in a temperature range from 20? C. to 300? C. of 4.5 ppm/K or less, and a T4 temperature, defined as the temperature at which the glass has a viscosity of 10.sup.4 dPa*s, at 1500? C. or more, and having a reboil propensity score of less than 10 measured in a reboil propensity test. The reboil propensity score is determined as a number of bubbles per glass rod formed from the glass after the reboil propensity test.

A submerged combustion melter includes a floor, a roof, and a sidewall structure connecting the floor and roof defining an internal space. A first portion of the internal space defines a melting zone, and a second portion defines a fining zone immediately downstream of the melting zone. One or more combustion burners in either the floor, roof, the sidewall structure, or any combination of these, are configured to emit the combustion gases from a position under a level of, and positioned to transfer heat to and produce, a turbulent molten mass of glass containing bubbles in the melting zone. The fining zone is devoid of combustion burners or other apparatus or components that would increase turbulence above that in the melting zone. The melter may include a treating zone that stabilizes or destabilizes bubbles and/or foam. Processes of using the melters are a feature of the disclosure.

A submerged combustion melter includes a floor, a roof, and a sidewall structure connecting the floor and roof defining an internal space. A first portion of the internal space defines a melting zone, and a second portion defines a fining zone immediately downstream of the melting zone. One or more combustion burners in either the floor, roof, the sidewall structure, or any combination of these, are configured to emit the combustion gases from a position under a level of, and positioned to transfer heat to and produce, a turbulent molten mass of glass containing bubbles in the melting zone. The fining zone is devoid of combustion burners or other apparatus or components that would increase turbulence above that in the melting zone. The melter may include a treating zone that stabilizes or destabilizes bubbles and/or foam. Processes of using the melters are a feature of the disclosure.

Controlling foam in apparatus downstream of a melter by adjustment of alkali oxide content in the melter. One method includes feeding a feedstock into a submerged combustion melter (SCM) apparatus having an internal space containing a flowing or non-flowing molten mass of foamed glass comprising molten glass and bubbles entrained therein, the molten mass having glass foam comprising glass foam bubbles on at least a portion of a top surface of the molten mass. The molten mass from the SCM is routed to a downstream apparatus, stability of the glass foam in the downstream apparatus is observed, and alkali oxide percentage fed to the SCM apparatus is adjusted based on the observation to positively or negatively affect the foam stability. Systems for carrying out the methods, and the products of the methods are also considered novel and inventive.

Controlling foam in apparatus downstream of a melter by adjustment of alkali oxide content in the melter. One method includes feeding a feedstock into a submerged combustion melter (SCM) apparatus having an internal space containing a flowing or non-flowing molten mass of foamed glass comprising molten glass and bubbles entrained therein, the molten mass having glass foam comprising glass foam bubbles on at least a portion of a top surface of the molten mass. The molten mass from the SCM is routed to a downstream apparatus, stability of the glass foam in the downstream apparatus is observed, and alkali oxide percentage fed to the SCM apparatus is adjusted based on the observation to positively or negatively affect the foam stability. Systems for carrying out the methods, and the products of the methods are also considered novel and inventive.

A low infrared absorbing lithium glass includes FeO in the range of 0.0005-0.015 wt %, more preferably 0.001-0.010 wt %, and a redox ratio in the range of 0.005-0.15, more preferably in the range of 0.005-010. The glass can be chemically tempered and used to provide a ballistic viewing cover for night vision goggles or scope. A method is provided to change a glass making process from making a high infrared absorbing lithium glass having FeO in the range of 0.02 to 0.04 wt % and a redox ratio in the range of 0.2 to 0.4 to the low infrared absorbing lithium glass by adding additional oxidizers to the batch materials. A second method is provided to change a glass making process from making a low infrared absorbing lithium glass to the high infrared absorbing lithium glass by adding additional reducers to the batch material. In one embodiment of the invention the oxidizer is CeO.sub.2. An embodiment of the invention covers a glass made according to the method.

A low infrared absorbing lithium glass includes FeO in the range of 0.0005-0.015 wt %, more preferably 0.001-0.010 wt %, and a redox ratio in the range of 0.005-0.15, more preferably in the range of 0.005-010. The glass can be chemically tempered and used to provide a ballistic viewing cover for night vision goggles or scope. A method is provided to change a glass making process from making a high infrared absorbing lithium glass having FeO in the range of 0.02 to 0.04 wt % and a redox ratio in the range of 0.2 to 0.4 to the low infrared absorbing lithium glass by adding additional oxidizers to the batch materials. A second method is provided to change a glass making process from making a low infrared absorbing lithium glass to the high infrared absorbing lithium glass by adding additional reducers to the batch material. In one embodiment of the invention the oxidizer is CeO.sub.2. An embodiment of the invention covers a glass made according to the method.

A low infrared absorbing lithium glass includes FeO in the range of 0.0005-0.015 wt. %, more preferably 0.001-0.010 wt. %, and a redox ratio in the range of 0.005-0.15, more preferably in the range of 0.005-0.10. The glass can be chemically tempered and used to provide a ballistic viewing cover for night vision goggles or scope. A method is provided to change a glass making process from making a high infrared absorbing lithium glass having FeO in the range of 0.02 to 0.04 wt. % and a redox ratio in the range of 0.2 to 0.4 to the low infrared absorbing lithium glass by adding additional oxidizers to the batch materials. A second method is provided to change a glass making process from making a low infrared absorbing lithium glass to the high infrared absorbing lithium glass by adding additional reducers to the batch material. In one embodiment of the invention the oxidizer is CeO.sub.2. An embodiment of the invention covers a glass made according to the method.