The history of glass making is covered in lots of books. This is not to try to rewrite history. My object is to help the bottle enthusiast understand some of the skills that Early Bottle Makers have had to develop to create the beautiful bottles that they made. My main interest is in the American bottle industry, but with its acquired skills that go back over 3500 years. The early bottle makers went through a lot of learning to get these skills developed.
I once found a writing of a Master Bottle Makers work stages to making a bottle. Now I can’t find it. These men had to know glass making from start to finish. The art of making a Hand Blown Bottle takes in all of the technology of the batch, the process of proper melting and blending of the glass batch in the furnace. The objective form of the container he needs to make. The physical concept of gathering a proper amount of glass and forming it into a parison shape that will blow out to the container he is making. Hand blown Bottles may be free blown or blown in a mold. This later forming has the hidden concept of shaping the parison properly to obtain good glass distribution of glass wall thickness when it is blown in the mold. He also has to understand controlled heat loss, because each stage of his forming has to hold its shape and be moveable in each stage of the forming process. It is a mystery to me how they developed these skills and I have collected pieces that I wouldn’t part with, because they represent the unbelievable skill shown in their forming.
The Master Bottle Maker worked with a group of associates; their efforts being done as a group at the SHOP by their glass furnace. The teamwork depended on each person’s skill and the team accomplishment of making a good bottle depended upon each of their own participation. The team consisted of a gaffer, the bottle maker, two attendants, and a carrier.
The team worked around a Bottle Makers Chair. The tools they used were very much the same as tools used for seven centuries, in many parts of the world. They included iron or steel blowpipes, punty rods, scissors, pucellas or tongs, shears and shaping tools, marver plates of either stone or cast metal that was flattened to allow the glass to be formed on them. The wooden tools were: the battledore (a paddle type of tool for flattening the sides or bottom of a parison), a wooden ladle, shovel, forming blocks, etc. These wooden tools were kept in water or kept wetted, to prevent them from excessive charring when used to form the hot glass. The carrier had a fork type of tool for carrying the finished product to the annealing furnace. Some times the carrier used a set of tongs that had wooden gripping pieces to hold and not mark the glass.
The gaffer would have preheated tools available. When the glass metal (the molten and blended glass material in the crucible) had been in process for the proper amount of time, the team would be ready to make glass products. He would insert a blowpipe in the glass metal and gather a gob of glass on the pipe. Passing this to the Bottle Maker – he would puff some air into the blowpipe and then seal his mouth end of the blowpipe with his tongue or thumb. The hot glass would expand the air that was in the hollowed gob of glass and the bottle maker would then be on his way to making a product. Often he would have to swing the blowpipe to stretch the neck glass to the desired length. The process of reducing the glass diameter at the neck was done by this stretching and twisting to take it to a smaller diameter. It often left marks and bubbles in the bottles neck.
The Bottle Maker would add more air and begin the process of making the parison shape for the bottle they wanted to make. During many of his stages of shaping the glass he would have to roll his blowpipe on the side rails of his chair to keep the molten glass concentric. Due to the glass temperature at this point the glass would settle if it wasn’t rolled until the glass skin temperature was cooled enough to make it hold. He would also have to shape it using his tools as necessary.
The blowing of a glass bottle requires a series of functions, on the part of the Bottle Maker that involve controlled heat loss. The melted glass starts out at over 2000 degrees F. and the parison shape has to be stable for inserting in a mold for the final blowing. If the bottle is being Free Formed, the key thing is still the distribution of the glass in the completed bottle form, as this is responsible for the containers strength.
If the parison shape is to be BIM (ie. Blown-In-Mold), the distribution of the glass in that mold is entirely dependent on what the Bottle Maker created in the parison glass shape. In my collection of old bottles I have some unbelievable examples of perfection that are hard to think they could have been achieved. Improper shaped parison form can cause heal tapped thinness in at the bottom of a bottle. It can cause unfilled shoulders near the top of a bottle. The formed parison that he has made, is the secret of having a good distribution of glass in the product, when the bottle is blown.
When this bottle is blown, it has to be removed from the blowpipe and the subsequent completion of the bottle involves the shaping and forming of the bottles finish (top) specification as needed. To accomplish this, the normal earliest method was to use a previous blowpipe with the neck glass of the previous bottle still on it. The gatherer would have reheated this glass on the previous blowpipe and he would assist the Bottle Maker by attaching it to the bottom of the newly formed bottle. This process is the empontilling operation. The Bottle Maker would then chill the bottle’s neck for cracking it off or shearing off the blowpipe. The gatherer would reheat the new bottle neck glass in the window of the furnace and give it back to the Bottle Maker. Depending upon the finish specification, the gatherer would pick up some glass from the crucible and prepare a ribbon of glass to be applied around the neck of the new bottle. The Bottle Maker would then be responsible for tooling or forming the hot glass to the desired finish specification.
Later the blown bottles were put in a sabot, snap case, or a shoulder holding device for the Bottle Maker to apply glass and tool it to the specified finish requirement.
After the bottle is made, a carrier has to take it from the Attendant or the Bottle Maker and place it in the annealing furnace. It might be of interest here to mention that glass is always a liquid even when its viscosity is near 0. As glass is formed and moved in the process of forming an object from the hot molten glass metal, the material is stressed much like moving a metal sheet in a punch press die. This stress can be seen under special lighting, and is relieved by the annealing process, after the bottle has been formed. If the glass were to be set aside without annealing the stress would eventually cause it to explode and break.
Early American Bottles were made from glass raw materials found near their glass factory. The furnaces were wood fired and the glass batch was melted in ceramic crucibles. The making of crucibles was a localized responsibility which needed a good clay source. Some early crucibles were imported to the Americas for glass melting. It was of course a very expensive source.
The early glass was a soda ash type of glass. The silica sand at each glass house was a little different in iron content and the soda ash was normally the wood ashes from the furnace. These glass products had inclusions of the unburned carbon and impurities that caused a lot of bubbles in the glass. This early glass is often referred to as “Mountain Glass”. The location of a successful glass house depended on a good supply of wood as a fuel. The clay and limestone plus transportation were all considerations for where a glass house might survive.
This early drawing illustrates a lot of the operations that I have covered above and is a good illustration of the 1800’s glass house. Click the image for an enlargement.