GLASS TERMINOLOGY
 

It is  my endeavors to bring toward the terminology commonly used in glass industry. It will result in better understanding the world of glass. It will  also bring exactness in usage of these terms.


Acid Etching

The process where the Glass Surface is made to react with Hydrofluoric Acid. This produce a uniform smooth satin like appearance. The glass also turns opaque.

Adhesive

A substance with the capability of holding two surfaces together by either chemical or mechanical interfacial forces or combinations thereof, bonding agent.

Adhesive Strength

The strength with which two surfaces are held together with an adhesive, also known as the bond strengths; quantitative tests are available for measuring the adhesive strength under various environmental conditions measured in units such as Pai or N/mm2.

Anti Reflective Glass

It is kind of a float glass with a special coating which reflects a very low percentage of light. It offers maximum clarity, transparency and optimum viewing through the glass.

Annealing

The process of cooling the glass in the integral part of the heating furnace or a separate furnace. This reduces the stresses formed in the hot glass due to slow cooling upto room temperature. A stressed hot glass subjected to rapid cooling can break easily due to thermal and mechanical shocks.

Bending

The process in which glass is softened by heating (6000C)and make it to turn along the curved mould to take the moulds shape. The glass is then annealed to remove stresses.

Bubbles

It is a pocket of gas or air trapped in the glass during manufacturing. These are the weak areas of glass. These bubbles are sometime introduced intentionally to decorate the glass. Paper weights are a good example.

 

Batch

It is the mixture of raw material Silica (SiO2), Sodium Carbonate, Soda Ash and Lime Stone that is put in one lot in a pot to make glass. The pot size and capacity determines the batch size.

Bevel

Cold glass (usually clear, thick plate) with edges that have been ground and polished to an angle other than 90 degrees. Transmitted light is refracted and a prism – like effect results. Bevels are available in a variety of sizes, shapes and geometric configurations (called “clusters”) for incorporation into leaded glass work.

Beveling

The process by which an edge of glass is finished to an angle. The thickness of glass is reduced gradually from inside to outside edge of the glass.

Bulletproof Glass

Armour plate glass which is more than 60mm thick and which resists penetration by bullets.

It is  my endeavors to bring toward the terminology commonly used in glass industry. It will result in better understanding the world of glass. It will  also bring exactness in usage of these terms.


Came

A metallic strip of Lead, Brass or Alloy with ‘H’ , ‘U’ ‘Y’ Shaped cross section used to join pieces of glass. Used mainly for windows and panels.`

Carving

It is a technique of removal of glass from the surface to form an object.3 D Glass Objects can be made with carving with the help of hand tools.

Casting

Name given to process and technique to form a glass in a mould.

Clamp

It is an agreement used to hold the glass to the work place. Clamping helps in accurate working on glass.

Cold Colour

Pigment as colour used to decorate glass at ambient (atmospheric) temperature.

Cold Painting

Applying of cold colours on glass to decorate it or create an image on the surface.

Cold Working

It is a term of describe the process of working on glass in cold (ambient) condition.No healing required like Beveling, Edging of Glass.

 

Coloured Glass

The glass which has colour.Colour can be due to

  1. Impurities during making
  2. Applying colour externally
  3. Adding various chemical during manufacturing to get colour (like metal oxides)
  4. Adding colour in the molten.

Cord

They are streaks or lines formed due to poor waxing of the batch .Cords are visible due different reflective indexes thus caused.

Cracking off

The process of detachment of glass object from the blowpipe or main mould.

Crizzling

It is a chemical instability in glass which is irreversible. It is caused by  imbalance of ingredients of the batch mainly excess alkali or deficiency of lime. This instable glass is affected by atmospheric moisture, which produces network of cracks on the surface. Technique are available to retard or shop.

Crystal

A terms used to denote colourless high reflective index , bright and brilliant lead glass .

Cutting

 A wide term used to remove the glass. To make controlled pieces of glass from sheet by use of automatic or manual methods .

Clutters

Glass cutters have diamond point to put scaring marks.Also tungsten carbide or hold metal wheels are used to scare the glass for cutting.

 

Decanter
A Decorative bottle with a stopper used to serve wine and alcohol .

Devitrification
During the annealing stage of fusing or slumping there is crystallization on the surface of glass due to cooling after the annealing point.

Die
A mould for glass made for metal.

Desicant
A hygroscopic (That substance which absorbs moisture)substance used to dry/remove moisture in insulating glass i.e. Micro sieve ,Silica Gel.

Distortiion
It is an defect on the surface of glass. It show a wavy optical effect.

Double Glazing
Two sheets of glass enclosing a hermetically sealed air space.

Decibble
Unit for sound measurement represented by DB.

Dichroic
Glass coated with ultra with thin layers of transparent metal oxides to increase the reflection by glass at specific wave length of light.As the angle of incidence of light changes varied bright colours can be seen in glass .


Dichroic Glass

Decorative Glass
Term used for glass on which processing has been done to increase the decorative properties of glass .Decorative Glass is used both inside and outside the building. Various process are used to make decorative glass, Stained glass, Coloring Etching etc

Decolourising
To negate the colouring effect of other material such as iron oxide present in the sand by addition of mineral like (manganese oxide).In the float glass batch. This process is known as decolorizing.


Drilling
It is the process of making holes in glass by the use of metal bonded glass hollow drills .

Diamond
Natural and synthethic diamond are impregnated intened to be used for Drilling. Sawing ,Edging , Beveling etc .Diamond tools can also be made by electrodepositing diamond, Diamond points are used on glass cutters to cut glass manually .

Dual Seal
When both primary seal (Mastic Buty)and secondary seal (Poly sulphide) are used to make insulated glass,the glass is said to be dual sealed.

Drawn glass
Glass made by ‘Faucault Process’ or ‘Pittsburg Process’. In this process the sheet glass is made by drawing the molten glass as a sheet direct from the fumace. The drawing rate determines the thickness of the glass

EDGING :

It is the process of working on the edges of the glass. Various edge shapes called edge profiles can be made on glass. This is done with the help of Diamond Tools.

EMBOSSED :

Raised or lowered text or design on any surface of glass is said to be embossed. The figure after embossing stands out from the surface.

ENAMELED GLASS :

It is applying of a vitreous substance made of finely powdered glass coloured with metallic odds and suspended in a medium for easy application with brush. Various figures and designs can be made on enameled glass.

ENGRAVING :

It is highly artistic work on glass. It is the art of making a design on glass by cutting into the surface of glass. Engraving methods use copper wheels, diamond tools, flexible shaft, grinders, various shapes and sizes of diamond bits. Fok wheels are used to polish.

ETCHING :

This can be accomplished on the surface of the glass by the use of Acid (HYDROFULORIC ACID). By the use of marking tape (VINYL TAPE) the desired pattern can be cut. The area exposed to acid gets opaque and deep thus giving wonderful designs and effects.

EDGE PROFILES :

These are the shapes made at the edge (thickness) of the glass. This adds to the decorative value of the glass. OG, Triple OG, Pencil Edge are few commonly used Profiles.


DIFFERENT EDGE SHAPES OF GLASS

 

Fibre Board
It is a high density fiber board used for insulation in kiln / furnace. Maximum temperature it can withstand is 26000 C. Usually 1 inch thick fiber board is available in various sheet sizes. Can be cut to suit  the requirements.


Fibre Paper
It is normally 1/8 of an inch thickness used for slumping glass. Maximum Temperature it can withstand is 26000 C. It is also used as Kiln wash. It is used to make moulds for fusion glass.


Flash Vent
A quick cooling step (turning off the Kiln and opening door for 3 – 8 Seconds).This removes trapped glasses and releases pressure build up.This action is taken at the end of final fusing / stumping but before annealing.


Flux (Fusing)
It is a substance that lowers the melting temperature for another substance. Potash an Soda are important fluxes.


Frosting
Obtaining an OPAQUE MATTE finish an glass surface  by exposing to hydrofluoric Acid, Ammonium Bi fluoride is also used for this purpose.


Fusing
It is the process to insert two or more pieces of glass in a Kiln or furnace until they bond to become one non separable piece. Heating of Enameled glass to bond enamel to the surface of glass is also called enamel fusing.


Furnace
It is an enclosed  structure to best glass. Heating can be done electrically or burning gas (LPG).


Felt Wheel
Used for final polishing of glass. Cerium oxide power is used along with these wheels. Generally of two types

  • Made of compressed Felts.
  • Made of compressed Felt with resin into strip

and then these strips are wound with adhesive to make a spiral wheel. Spiral Felt wheels have a longer life and can work at higher speed.


Fibre Glass
Consist of fine strands of Glass used to form glass wool for insulation and lining of kiln , furnaces and incubators.Also used for matting and reinforcement. Jet of stream and air are blown as the glass flows out of the tank furnace through very fine small diameter nozzles, resulting in glass to become thin strands.

Flat Glass
All types of Glass (rolled ,float, sheet etc) independent of the production process are flat glasses.

 

GLASS BULLETINE JAN - MARCH 2007


 
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