There are two methods of glass blowing that were created when the art of glassblowing was invented. The very first one was free-blowing and the second is Mold-Blowing. I will first talk about free-blowing; this method was the first method of used when the invention of blowing glass first started and it is widely used today for forming glass and artistic uses. To perform the free-blowing method you would the normal process of gathering your molten glass to place at the bottom of your blowpipe/steel pipe but instead of shaping and molding it you blow short puffs of air into your molten glass.
Once you had created a bubble or spool at the end of your blowpipe the molten glass creates this elastic skin kind of effect on the interior of your glass blob and it matches the exterior skin of your glass blob by removing it from the heat of your furnace. Then from there you can then quickly inflate your molten glass to a blob that you can work into the desired shape of your glass piece. The best example of a product that was created through free-blowing is the Portland Vase; this was first created in the Roman period. Now the free-blowing is what is used when creating other vases, pipes, glass pitchers and bottles.
The second method is Mold-blowing; this was created as alternative method in glass blowing. It was created the second quarter of the 1st century AD. The process of mold-blowing can be done after gather of your molten glass that you placed on the bottom of your blowpipe, then you inflate your glass and place it into a wooden or metal carved mold. This mold adjusts the shape of the glass and texture to the blown glass bubble. There no talent required in performing this method, it is very simple and straight forward. There are two types of molds that can be used when performing this method. The first mold is a single-piece mold and the second is a multi-piece mold. With the single-piece mold it is simple on designed mold that you place the glass in and remove in one solid movement.
The single mold gets used a lot for the making of tableware and utilitarian vessels. For as multi-paneled mold or also known as the multi-piece mold is the same way to produce it but the mold itself is different. It is has much more details in the mold to create a more unique design and shapes for the glass piece being made. It is as it says in its own title multiple pieces of panels are placed in the mold to give it the designs and texture of the glass piece that is being created. The multi-paneled mold is used a lot today in the fancy cups and pitchers we see that have detailed designs along the sides.