The Float Process (2024)

FAQs

The Float Process? ›

Molten glass, at approximately 1000°C, is poured continuously from a furnace onto a shallow bath of molten tin. It floats on the tin, spreads out and forms a level surface. Thickness is controlled by the speed at which solidifying glass ribbon is drawn off from the bath.

The Float Glass Process is a multi-step glass manufacturing process where liquid glass is formed by "floating" it on molten metal. First, raw materials are weighed, mixed and moved by conveyor from the initial batch house into the furnace. Water is added to help mix the batch and minimize airborne dust.

Float glass is made by pouring the molten glass from a furnace into a chamber that contains a bed of molten tin. The process is sometimes call the Pilkington Process. The atmosphere inside the chamber is carefully controlled. The glass floats on the tin and forms itself in the shape of the container.

Float glass manufacturing is one of the highest temperature industrial processes. Both sand and recycled glass need to be heated up to 1600°C to form a ribbon of molten glass. The molten glass then floats on a bath of melted tin to guarantee planarity and control thickness.

But it wasn't until the late 19th century that float glass came into being. In earlier centuries, glass was made by the blown and disc method. As glass used to be made only for windows, window glass or other flat glass was made from large discs of crown glass or blown glass bottles.

Once produced, float glass is cut to the required size, before undergoing further manufacturing processes such as tempering. Float glass if broken, will shatter into sharp-edged shards. Thus, for safety reasons, special care should be taken when considering using this product.

1/4 to 3/8 inch thick "clear float" glass is commonly used to protect furniture - desk tops, dressers, nightstand, coffee tables, etc. The cost for this type of glass is typically more than $7 per square foot, with the most common customization being edge cuts which increases the price further.

Float glass is characterized by great surface hardness, but is very fragile and UV transmittant. Tempered safety glass and laminated safety glass are special forms of float glass that provide enhanced mechanical and chemical resistance.

However, float glass has a couple of downsides: it is extremely fragile, has low strength and durability and when shatters it does into pieces of sharp shards.

We can thermally temper float glass down to a thickness of 3 mm, which means that the glass no longer splinters into sharp pieces, but instead granulates into small blurry pieces – a feature known from the side windows in cars.

What is the raw material for float glass? ›

Float glass uses common glass-making raw materials, typically consisting of sand, soda ash (sodium carbonate), dolomite, limestone, and salt cake (sodium sulfate) etc. Other materials may be used as colourants, refining agents or to adjust the physical and chemical properties of the glass.

Float glass is quite inexpensive but it cracks and breaks easily. We do polish float glass in certain situations, but due to the risk of breakage, a straight out replacement is often recommended.

Float glass is a substance composed primarily of Si, Na, Ca, Mg, Al, K, Fe, Ti, S and O (commonly called “soda lime silicate” glass). Pb, Cr, As, Sb, V may be present in float glass as trace level contaminants, always below 20 ppm. Tinted glass may contain Co, Se or Ni, up to 200 ppm.

Glass formation usually takes place by rapid cooling of the molten mass past the crystallisation temperature and the solidification starts at the glass transition temperature. This process is usually described on the basis of change in enthalpy or volume as a function of temperature as shown in Fig.