The Raw Glass Production Process

Posted on 04/05/2012 by Christian

In our current blog we describe the manufacture of raw glass (lime soda glass). Normally the following raw materials are used for the glass mixture:

The ingredients change according to the type of glass being made. This list therefore only features the most important components. As soon as the batch is made, the melting begins with 3 different phases:

Phase 1 is the preliminary melting phase. This is when the batch is melted and homogenized
Phase 2 is refining (removing gas bubbles).
Phase 3 is cooling down the material in preparation for forming

The glass components slowly begin to melt together at temperatures around 1400 degrees Celcius. The melting is facilitated by injecting air or gas into the process. Refining takes place right after melting where remaining gas bubbles are removed. Since melting can be rough and can reach very high temperatures this process takes a lot of time. Refining is also a determining factor of quality. The forming comes once this process is over. Forming is only possible at lower temperatures. This process varies according to the type of glass being manufactured or the application.

Glass can be formed by extruding, blowing, spinning, rolling, pressing or drawing (see also Finishing techniques):

Hollow glass is made using several techniques such as pressing, blowing, suction and a combination of these methods
Fiberglass is produced by, among others, extrusion and drawing techniques
Flat glass is made using float glass methods, it is drawn, rolled or cast
Glass tubes are made using drawing techniques

Once the forming process is done, the glass must still be cooled. It is important to watch for stresses that occur during forming. These stresses occur because of the different expansion rates of the materials. These stresses are measurable with an optical stress viewer. Stress sensitivity is dependent upon the expansion coefficient of each type of glass. By constant cooling, or annealing, these stresses are starkly diminished. Depending on the glass type and thickness, the time it takes this process to finish can really vary from a few hours up to several days. Special kilns or industrial cooling paths perform this job.

Glass Lenses

Posted on 11/04/2012 by Christian

A lens is an optically effective element with two light-refracting surfaces. Of which a surface is usually curved as concave or convex. The most important characteristic of a lens or a so-called lens system is the optical image. The critical size of a lens is the focal length the unit is specified in meters, depending on the intended use etc. Thus the distance from the focal plane or the focal point of the lens is defined. The simplest lenses are optically active at both spherical surfaces (surface sections of a sphere). From a historical perspective it is assumed that the first glass lenses were used in the field of optics. They were used as lenses to correct short sight or long sight. Later, the first binoculars and also microscopes were developed. Materials which are suitable for the production of lenses must be made of transparent materials. In addition to glass are also some plastics suitable, such as Polycarbonate. The name of the lenses is defined by the curvature of their surfaces. Each of these surfaces can be concave, convex or flat (plan). Convex lenses have curved surfaces outwards, concave lenses, however, have inner curved surface. With lenses having a flat surface no curvature is present. A very important characteristic of a lens is the principle of reversal of the light path. The focal length is dependent on the curvature radii of the two lens surfaces. There are many different types of lenses. We want to enumerate only a few at this moment.

Fresnel lens (e.g., Daylight projectors, headlights, etc.)
collecting lenses (two convex or with one convex / flat surface)
diverging lenses (two concave or with one concave / flat surface)
meniscus lenses (one concave and a convex surface)
spherical and aspherical lenses
cylindrical lenses (e.g. glasses, wide-screen cinema projectors)
elastic lenses

The company Schäfer Glas GmbH manufactures glass lenses in different forms and for many different applications. Thereby we consider primarily the needs and desires of our customers to realize the finished product. It starts with an idea. In general, we receive a technical drawing from our customers. An appropriate tool must be made for the production of a glass lens in the molding process As soon as the tool is ready, we can produce the first samples for inspection and testing. It is our aim that we realize our customers’ complete satisfaction. Through our long years of experience and continuous development, we are able to produce glass lenses with high accuracy while achieving an appropriately high standard of quality. Whether small numbers or large quantities – our flexibility opens up leeway for the needs of our customers.

Glass beads – multiple applications

Posted on 07/03/2012 by Christian

Glass beads play a prominant role in our wide-ranging assortment. Just the variety of possible applications are an indication these days that glass is an important component of daily life. If we look at our assortment, it’s easy to miss the smallest glass beads left in our production sites all over the world. Each one has exactly a 1 mm diameter and we make them in Germany following a traditional process. The scale of these small borosilicate beads can also be expanded – 2 mm, 3 mm, 4 mm etc. There are several possible applications for these beads. Among other things, they are found in ball bearings, as a mixing ball for insulin, as a ball valve in a dosing pump and in dispensers in the grocery and cosmetics industries, etc. Our outstanding quality and precision is valued around the world.

But the small borosilicate glass beads or even the lime-sodium glass, are not the only things in our assortment. We also produce larger glass balls up to a diameter of 150 mm in different colors and designs. These glass balls are available with blind holes or through holes, or without holes. Being able to meet the demands of our customers is one of our strengths, so hole diameter and depth are not a problem for us at all. These balls are applied in stair rails, door handles, and curtain rod end caps, etc. and are available in many lovely colors. Whether red, green, light blue, dark blue, yellow, orange or …. – our very high quality turns every object that uses our glass balls into something really eye-catching.

Our glass balls are also available in different sizes as bubble glass balls, i.e. so that the inner part of the bead has larger and smaller air bubbles. These and all glass balls can also be furnished with a display case. This allows the beads to be used as decoration or as an eye-catcher at the base of rails. We also offer half glass balls that can be used in interior design, for example. These half balls are also available in many different sizes and colors.

Glass – an extraordinary material

Posted on 07/02/2012 by Christian

Glass is a material with a long history. By about 5000 BCE, natural glass called obsidian, was used as a working material. Blades, wedges and scrapers were fashioned and used to make other objects for daily use.

Glass was fashioned into containers in Egypt from approx. 1450 BCE. The Egyptians were the ones who first discovered how to make glass. From that point on, glass making developed in leaps and bounds. In the Roman Empire, villas for the upper-classes were outfitted with window glazing. This was made possible by the invention of the glass blowing pipe in approx. 200 BCE.

This means that the first center for glass production arose during the 11th century in Venice and reached its fluorescence between the 15th and 17th centuries. Glass makers at this time settled on the island of Murano. And today Murano glass is still synonymous with extraordinary glass art. And this is how glass production continued to develop through the centuries until today.

The Schäfer Glas GmbH company, is now making its third generation of different products out of glass. Our products are made predominantly through a glass molding process with the greatest care and according to tradition. Long-standing experience, quality consciousness and innovative products are the cornerstones of our success. We constantly develop our production process to continuously improve our good market standing. The fascination that comes from working with this extraordinary material is the driving force behind our company.

There are many different types of glass. In making our products, we predominantly use soda-lime glass (for ordinary use) or borosilicate glass, which because of its chemical and heat resistence is among the glasses employed especially in the fields of medicine and chemistry. Our borosilicate balls, which we produce ourselves from as small as 1 mm, are known around the world and are distinguished by their outstanding quality.