Category: Types of Crystal

The Manufacturing Process of Crystal

1. Mix crystal and red-lead oxide

   The crystal “cocktail” is mixed and made into molten crystal in a furnace heated to 2,192 F (1,200 C). The red-lead oxide is introduced into the furnace on a rapidly moving air current in a difficult procedure that can create different grades of purity. The furnace conditions must also be carefully controlled so the lead fully oxidizes and doesn’t leave metallic lead, which not only discolors the glass but also attacks the fireclay of the furnace. The lead adds density to the glass so it is heavier; this weight advantage over ordinary glass also changes the crystal’s light diffraction properties and the sound or ring of the crystal when it is struck.

2. Create the basic shape

   Lead crystal is blown glass, but, because of its thickness, it requires a team of four to seven artists who are as well coordinated as any team of athletes. Wood blocks and molds are used to create the basic shape of the object called a crystal chamber. As soon as the molten glass touches the mold, it begins to cool instantly so glass blowing is a process of seconds. The chamber is also known as hollowware because it has an opening that is the functional part of the beverage glass, vase, or decanter.

3. Blow Glass

   The team of glass blowers uses physical strength, breath control, and dexterity to create the chamber with a certain thickness. This skill is only developed by experience. The thickness must be suitable to the object itself but also to the depth of the facets that will be cut in the glass. Near the furnace, other parts are added to the chamber. For example, a piece of molten glass is attached to the side of a decanter to form a handle and shaped to the perfect curve in one quick motion. Again, the glass will begin to harden almost immediately in the open air.

4. Aneal

   To slow that hardening process, the blown crystal piece is transferred to an annealing oven. If the crystal cools too quickly, stresses will be induced in the crystal as varying thicknesses cool differently and the crystal will contract too rapidly. The annealing process takes from 2-16 hours depending on the size and configuration of the piece.

5. Cut

   The cooled crystal is now a “blank canvas” for the glass cutter. To prepare for cutting, the pattern is drawn on the vessel, usually with red-lead and turpentine. The design is then roughed out with a power-driven wheel equipped with different edges depending on the type of cut required. These cut surfaces are coarse and not as long or as deep as the finished cuts. The cutters are true artists who use sight, feel, physical strength, and their extraordinary memory for patterns, details, and cuts. The types of cuts are wedge and flat cuts. Wedge cuts are made with diamond-tipped wheels and produce deep facets. Flat cuts are made with the same equipment but are not as angled; they provide contrast with the deeper wedge cuts.

6. Smooth

   In the smoothing process, a sandstone wheel is used to dress the rough cuts; this part of the process requires the greatest skill because it establishes the finished design.

7. Polish

   Finally, the finished vessel is polished by dipping it into a mixture of sulphuric and hydrofluoric acids. The acid bath attacks the entire surface of the object and removes a very thin layer while leaving a lustrous and uniform finish.

8. Etch & Engrave

   The process of intaglio, which uses tiny copper wheels that revolve slowly to engrave portraits or other illustrations and information into the object, is also used to engrave some pieces. Most engraved pieces, like large sports trophies, are one-of-a-kind items that are completed on commission. They may require many hours of etching. The finished piece is carefully inspected and packaged in materials designed to display and protect the object.

Crystal Quality Control

Quality is a continuous process at the lead-crystal factory. The artists themselves provide the first level of quality control through their experience and unique skills. No two pieces are identical despite adherence to designs, heritage, and standardization of patterns and cuts.

Stringent inspections are performed at each step of the process. This helps avoid wastage in that in imperfectly cooled piece is never sent to the cutter; inspections also ensure conformity with the acceptable range of variations that are inevitable in handwork and among individual cutters and other artists.

Byproducts   Waste

There are no byproducts from production of lead crystal. Waste is avoided in raw materials and by careful control of processes like annealing. Glass factories have the advantage that their products can be melted again in the furnace, so many boast that they produce no seconds because of this luxury of being able to fully recycle an imperfect product.

What Makes Glass?

Glass is made using three different minerals:

1. Sand (silica)
   Intense heat changes sand into a fragile form of glass.
2. Soda ash (sodium carbonate)
   This is a powdery white material that is added to the mixture to lower the melting temperature of the sand.
3. Limestone (calcium carbonate)
   This is added to make the glass stronger.

The raw materials are melted together in a furnace at a temperature of 1600 C. This is the same temperature as a jet engine!

What Makes Crystal?

The inclusion of at least 24% lead oxide in the composition is required by law for crystal to be called full lead crystal. The lead lends brilliance and weight to the product. Crystal without lead is still crystal, i.e. clear glass, however, it is more commonly perceived as “glass”. The lead also make the crystal softer and more conducive to cutting. This is why the lead crystal is cut and for the most part, the unleaded crystal is not cut.

Optical Crystal is 100% Lead Free and extremely hard. It is this hardness that provides the basis for the brilliant cuts and bevels, as well as the ultra high polished surfaces. Each piece of Optic Crystal is hand polished and beveled. Optical /Optic Crystal, as clear and as flawless as used in binoculars and camera lenses, represents the ultimate expression of excellence. Optical Crystal is manufactured in large sheets up to 3″ thick, and while still molten, is subjected to tremendous pressure to ensure no bubbles, flow lines or other distortions. What an ideal way to recognize achievement and express appreciation.

Optical Crystal is a completely Lead Free material. Make a patch against Lead Crystal, optical crystal is more transparent and hard. Also it can be cut with special shapes. With this lead-free optical crystal (optic crystal) be handmade by high-quality handicrafts, brilliant crystal awards, trophies, crystal crafts, crystal gifts, paperweight, crystal jewelry, crystal beads, crystal balls, recognition corporate awards and crystal parts are made perfectly.

Optical Crystal Manufacturer

1. Ravenscroft CrystalThe public now understands that lead-free crystal is the future of the glass industry. Ravenscroft is the world’s leading manufacturer of hand-made, pure, clean, lead-free crystal for fine wine and spirits. Their 129-year-old European factory has been producing lead-free crystal for the most exclusive brands of the world. Most likely, you have enjoyed the delicate pleasure of their products under another brand name.”Pure, Clean Crystal” Over the past four decades, wine and spirits glass design has experienced a renaissance. Recently, scientists discovered the dangers of lead crystal, most significantly when storing wine and spirits for an extended period in decanters, allowing lead to leach into the contents. Originally, lead oxide was added to glassware as a manufacturing aid. Now, technology has progressed to the point where the addition of lead delivers little or no value to the wine enthusiasts’ experience. Despite increasingly stronger industry warnings, several of the world’s top stemware manufacturers continue to use lead in production.Ravenscroft Crystal’s time has come.
2. Crystal CentralCrystal Central is an online crystal store specialized in optical crystal award & gift. It offers customers with a better & informed award buying experience. You can easily relate the generic crystal award & gift pieces to your specific recognition need with their extensive online award & gift samples. The recognition award ideas are categorized by recognition occasions for easy browsing.

Overview:

The manufacturing of glass is an art and process established over 2000 years ago and uniquely has changed very little apart from the addition of lead to create today’s lead crystal. Lead crystal usually comprises of 48% silica sand, 24% potash and 28% red lead. The mix creates an optimum balance of clarity, weight and hardness. With its complicate manufacturing process and exceptionally high perceived value, the lead crystal has been sought after and treasured for generations, and remains a status symbol even today.

The lead crystal formula is mixed and turning into molten crystal in a furnace heated over 2000F. Red lead is added into the furnace to create the purity and density.

Lead crystal is blown glass but because of its weight and thickness it requires a coordinated team of blowers. They use their skill and experience to create the glass body to the correct thickness. This is necessary to enable the glass designs to be deep cut. At this time other parts such as handles can be added.

The pieces are then placed in an annealing oven – under controlled conditions the oven slowly and evenly heats the glass to an annealing temperature. After a brief soaking period to ensure even heat distribution throughout the glassware, the oven temperature is slowly returned to room temperature.

The lead crystal glass is now ready to be cut. A pattern is drawn on the items and then mapped out with a power wheel. The finished design is then completed using diamond tip wheels using a combination of flat and wedge cuts to provide contrast, followed by the smoothing process on a sandstone wheel.

To finish the items it is dipped into a combination of sulphuric and hydrofluoric acid which removes a thin layer of glass providing a uniform and luster finish.

History of Lead Crystal:

Like many cultural advances the history of glass and crystal began with the Roman occupation of Britain and eventually reached a high point in the stained glass windows of the middle ages. In the 1500s new skills were added when highly skilled glassblowers moved to London from Venice and attracted royal patronage from Queen Elizabeth.

In the mid 1700s George Ravenscroft started his own glass business in London and patented the formula for producing lead crystal. He found that adding lead to glass during the melting process improved the quality. During this period the art of creating patterns by cutting became established and lead crystal was a perfect medium for the art. Many businesses perfected the process and lead crystal and glass became popular creating an established industry. However in the time honored process of all governments they recognized an opportunity for raising taxes and stunted growth and created many closures in the lead crystal sector.

English manufacturers moves their factories to Ireland to avoid taxation and during the period Ireland became the center of lead crystal manufacture, especially in Waterford, where the famous Waterford glass factory was developed in the 18th century. Unfortunately the Irish tax authorities saw an opportunity to raise taxes and forced many of the companies out of business. Waterfords for example did not start trading again until after World War 2. In the meantime during the 19th century other companies in France, Sweden, Italy (Venice), and Sweden were establishing their reputations and creating famous brands such as Orrefors, Baccarat and Swarovski.

Most fine crystal contains lead oxide. 24% is the optimum percentage for color, weight and hardness, while still ensuring clarity, sparkle and brilliance. 24% Lead Crystal, with its exceptionally high perceived value, has been sought after and treasured for generations, and remains a status symbol even today.

Sample Lead Crystal: