THE CREATION OF GLASS
Over 4,000 years ago, perhaps on the sands of Egypt, Syria or Babylonia the creation of glass began. Since then mankind has added, little by little, to the glassmaker's art. The skill of the glassmaker has been a source of beauty, treasured by all.
It is natural that you, a Tiara Associate, should want to know something about the way glass is created. Making glassware by hand is the oldest industry in America, started in the Jamestown Colony in 1608. Many of the techniques and tools of the early days are used in the manufacture of Tiara items. Each item is exclusive with Tiara and will not be found in any other line.
Glass is truly the product of earth and fire! Made of silica, soda ash, lime and feldspar, small amounts of various other chemicals such as copper, selenium, manganese and cadmium are added to make a "batch". After careful mixing of the selected ingredients, a quantity of broken glass - called cullet - is often added to the "batch" to speed up the melting process.
At the Indiana Glass Mold Shop, the primary concern is keeping mold equipment in a good state of repair. However, new molds are also produced here.
A design for a new mold is first worked out on paper, with the necessary consideration given to requested specifications, design factors and machine capabilities. A wood pattern is then generally made to show the entire mold as it will finally be produced.
The final molds are made of cast iron, consisting of a bottom plate, a body mold, [one piece block mold or joint mold] a ring and a plunger.
A complete set of molds can range in cost from $9,000 to $50,000 depending on whether they are hand or machine molds and the size and complexity of design for the item to be produced.
Machine molds range from 12 to 40 molds per set and it is estimated that we have approximately 2,500 complete sets.
Hand molds generally have two molds per set. We have approximately 1,500 sets of hand molds.
With the use of color variations, grouping variations, etc., it is possible to produce thousands of different items.
Due to extreme heat, pressure, and corrosiveness of materials used in making glassware, it is necessary to clean the contact surface of the molds each time they are used. Various polishing stones and air grinders are used to thoroughly clean and polish the molds.
The joints of the molds are continually being worn away and must be welded and carefully rematched by hand.
Indiana Glass Company employs a highly skilled group of individuals in the Mold Department who are dedicated to the excellence of the finished product demanded by the discriminating customer.
THE PRODUCTION OF GLASS HAND
Hand blown and hand pressed glassware has been produced in this country for almost two hundred years.
Two types of tanks are generally used in the hand made production of glassware - day tanks and continuous tanks.
The tank into which the glassworker shovels the "batch", has been pre-fired to an intense heat of about 2700° F. In about 18 hours, the glass is ready to be gathered and blown.
Day tanks hold only about 5 tons of molten glass. They are filled with batch material and melted for 16 hours, then worked for only 8 hours each day.
Individual "shops" consisting of anywhere from 6 to 18 individuals are arranged for the production of a handmade or mouth blown item.
A man called a gatherer standing on a platform, holds a long rod called a gathering rod. This rod is placed into the tank and rotated in one continuous motion. This causes the glass to gather on the end of the rod. The rod carrying the glass is then transferred from the tank to the cast iron mold. The presser, or the man standing in front of the mold with shears, cuts the correct amount of glassware from the rod. The amount of glass cut normally varies no more than 1/4 of one ounce.
The presser then slides the mold under the plunger and pulls the lever which moves the plunger into the mold. After a predetermined amount of time the plunger is released from the mold. The mold is removed from beneath the plunger, opened and the piece of glassware is removed. The take-out person places the ware in a device called a "snap". The ware is then transferred to a "glory hole". The amount of fire contained in the glory hole impacts a beautiful lustre to the glassware and at the same time makes the glass pliable enough to be finished. The final shaping of the article is done by the finisher.
Immediately after the ware is finished, it is taken to the lehr. After passing through the lehr, it is carefully scrutinized by an inspector and packed for our customers.
In the machine manufacture of glass, lime, soda ash and sand are mixed with broken glass and fed into the end of a furnace.
A gas flame coming from the side above the melted glass keeps the material in the tank between 2700° and 2900° F.
In the furnace gas flames from side ports go across the surface of the glass and into a heat chamber or regenerator on the opposite side. Every 20 minutes the direction of firing is reversed to take advantage of the heat that accumulates in the regenerators on each side.
The melted glass then passes through the tank throat into a refining chamber where impurities are further melted out. Several long fore-hearths or feeders lead from the refiner where the temperature of the glass is reduced to approximately 2000° F. The glass at this point is pushed through an orifice and cut off by shears into uniform gobs. These gobs are pressed by a plunger into the shape of the article being manufactured.
The ware is then cooled by air to the point where it can be transferred into the glazing operations.
Glazers serve a dual purpose. Firstly, they enable the fire polishing of the top edges and side walls of the glassware. Secondly, the glazers are a means of delivering the ware to the front end of the annealing ovens.
Inspectors at the other end of the annealing ovens are examining each piece and sorting carefully, removing the bad ware.
At first an inspector may keep 20% and discard 80% of the ware produced. Over a period of hours, however, adjustments are made so that approximately 85% of the ware is of excellent quality.