Glass products are used by melting one or all of three rather inexpensive and readily available ingredients including sand, soda ash, and lime. Additives are added to the mixture for strength and for altering the color. The mixture is heated to over 1000 degrees Fahrenheit, which ultimately turns the mixture in a syrup like matter known as molten glass.
How Glass Containers are Made
Bottles, jugs, carboys, and demijohns are made in one of two ways from here including air blown, and molded or pressed. For the air blown method, air is blown through a tube into the center of the molten glass. A balloon begins to form from the pressure and increases in size. This is done within a mold, and as the balloon expands to the reach the mold, the outer shape of the vessel is formed. Alternatively for the pressed or molded variation, there are molds the the contain both the outer and inner shape of the glass. The molten glass is poured into the mold and allowed to consume all of the cracks and crevasses, forcing the air out. In both cases the mold is put into an annealing oven to cool slowly. A rapid reduction in temperature will result in cracking or shattering of the glass. The molds are made up of 2 or more pieces that come apart, leaving a beautiful piece of art.
Glass Carboy Manufacturers
The larger carboys of this type have little demand. Glass carboys are primarily suited for the wine and beer hobbyist, and as you might suspect this does group of people do not lead global trade discussions. For any vessel or container that is applicable to the industries with labs, or those with cleaning and storage needs, there is a plethora of manufacturers and products. Namely in the plastics and metal drums space. A 5 gallon glass carboy, however, is not ideal for these applications. Therefore the number of manufacturers for large glass containers in the space have dwindled over time as plastics offer cheaper production costs, better durability, and are formed into different shapes suiting those industries. This has caused a fairly recent spike in prices as one of the major manufacturers in North America and Mexico (Vitro Packaging Inc) has stopped production.
Glass Carboy Types
Glass carboys can be found in three basic varieties including jugs, carboys, and demijohns. The vary both in shape and size.
Jugs come in 1/2 gallon and 1 gallon sizes. They can be used in the same way as larger fermentation containers with the use of a fermentation lock or airlocks. The size itself will offer some advantages and disadvantages. The small form is ideal for experimentation using different yeast cultures on a small scale. A singe batch can be split up, different yeast strains applied, and allows for a very convenient way to test batches without the commitment of using a full batch. Also the size of the containers allows for it to be conveniently placed in a refrigerator for fermenting lagers which require lower temperatures. They are generally equipped with a handle making for easy transport and movement. And once fermentation is complete, they are reusable and great for temporary storage of beer for taking some to share with friends.
The same advantage in some ways is also a disadvantage. The size is not ideal for fermenting a full batch of brew, for example 5 gallons. It will create more work to deal with numerous jugs, there will be more variation due to yeast distribution, and you will be investing in airlocks. Its just not going to be a long-term best practice for brewing.
Jugs have a much wider array of usage by many industries, and with this demand, there are many manufacturers. This helps with driving prices down. They come in different shapes and colors. You will also find varying wall thickness. A general idea for pricing can be found below.
|Glass Jug||0.5 gallons||$2.75 - $7.95|
|Glass Jug||3 gallons||$3.20 - $6.95|
Carboys are the term for larger vessels and can be found in sizes ranging from 2.5 gallon to 6.5 gallon. The thickness of the walls are generally 1/4" thick, but variations will be found, especially in older bottles. There are variations in the shape of the carboys and include both smooth outer texture and ridged. The ridged texture is especially helpful when handling the carboy when wet, as it helps with grip. Also, some glass carboys can be found with a greenish tint.
Below is a table of available glass carboy sizes, and illustrates some prices that can be found around the web.
|Glass Carboy||2.5 gallons||$12.99|
|Glass Carboy||3 gallons||$17.92 - $29.95|
|Glass Carboy||5 gallons||$21.90 - $35.90|
|Glass Carboy||6 gallons||$23.89 - $44.95|
|Glass Carboy||6.5 gallons||$24.89 - $47.95|
Demijohns have been around for hundreds of years. Before modern packaging and branding generic glass containers were used for storage, transport, and sale. They were commonly used for oils, vinegar, wine, spirits, as well as beer.
Although they come in different shapes there are generally wide and rounded at the bottom like a pear, with a narrow neck that is longer than that of a carboy mentioned above. Demijohns are also normally smooth and slick. One of the most noticable features is that what accompanies it, and is the weave support. Today these may have an internal steel framework, that is wrapped for its appearance. Demijohns, especially older ones come in various colors, and clear is common and readily available. Demijohns are also made with taps or spigots at the bottom. And the weave around the bottle will have an opening or trap door to expose the tap.
For brewing some of the advantages of demijohns is their variety of sizes. They range from 1/2 gallons to as high as 15 gallons, although more common sizes found in home brew stores are 14.25 and 15 gallons. For brewers that do multiple batches in a single shot, this can provide some clear advantages which include: A single fermentation vessel (less equipment), better ability to siphon more liquid without reaching into the bottom of the bottle (Where the resting sediment ends up), and a weave or sleeve that protects from light.
Demijohns are more common in Europe and Asia, as such many of the manufactures live there. This impacts pricing for those in the United States. Vetraria Pescia is one such company, and you can see different model on their website.
Below is some information showing prices and features that you will find around the web and in your local home brew stores. One note on pricing, is that some of these bottles have been around for a long time and are considered antiques. These can fetch extremely high prices. These collection pieces are not included below.
|Glass Demijohn||5 gallon||With Spigot||$57.95|
|Glass Demijohn||14.25 gallon||With Plastic Weave Basket||$49.00 - $79.99|
|Glass Demijohn||15 gallon||With Plastic Weave Basket and Spigot||$75.85|
Advantages of Glass Carboys
There are reasons that would bring glass carboys to the forefront of decision making, please see below:
- Transparency - The transparency through glass is like no other. The swirling currents of yeast activity can be seen with such visual precision and clarity that you can stare into the fermentation process and get lost in the ever changing swirls of ebb and flow. Watching this flux gives indication of the activity of the yeast from its rise and to it's fall.
- Scratch Resistance - Scratches to the fraction of a millimeter are enough to damage the fermentation process by allowing breeding grounds for fungus and bacteria. Most glass is made with only 0.5 % of its theoretical strength. Even so, the strength of modern glass allows it to defend from three dimensional perforations in its surface far more than plastics. Although these abnormalities can be formed through the manufacturing process, and usually indicate point defects, or structural inhomogeneities caused by fluctuations in the composition itself. Never the less, glass' resistance to forming new scratches are unlikely from the brewing process, or the tools used to clean them.
- Longevity - If a glass carboy is not dropped or accidentally chipped, it will stand the test of time and be usable for your lifetime. As mentioned demijohns have been used for hundreds of years, and these relics and antiques are actively traded today.
- Non-Permeability - Porous or permeable materials allow the atmospheric air to leech into the fermentation vessel. This introduces bacteria, as well as oxygen which can damage a beer in its transition. Glass is non-permeable, and this means that it provides the protection needed for controlled fermentation.
- Heat Tolerance - Although the rapid change in temperature can cause a glass carboy to crack (thermal shock), if eased up or down at a reasonable rate, glass can tolerate extremely high and low temperatures. Carboys will be able to withstand temperatures in the hundreds of degrees, and tempered glass will withstand more.
Disadvantages of Glass Carboys
- Cost - As mentioned, the number of manufacturers for glass carboys is dropping, or they may only be found overseas, depending on what you are looking for. While smaller jugs are very reasonable, carboys and demijohns raise cause for concern. Their plastic counterparts easily beat these prices.
- Weight - The weight of glass is heavy. As mentioned demijohns are commonly accessorized with weave baskets with handles for moving the containers. This weight has more of an impact that you might suspect when dealing with the carboys for the brewing process. Some examples of when weight will matter includ filling the carboys with water (potentially at a remote location), dumping the carboys into the boiling pot, moving the carboys up or down stairs, and cleaning. Not to mention the bare weight of the glass will impact shipping costs. This is not so green as it increases fuel costs.
- Shape and Size Variance - Due to the manufacturing process, it is extremely likely that no two carboys are exactly the same. There is a lack of precision markings on the containers for measuring. If part of your process is eyeballing, you will have differences when working with glass carboys.
- Potentially Hazardous - For anyone who has been injured by broken glass, or who has watched a carboy shatter before their eyes, it is obvious to see how a carboy could cause severe damage. The large shape of a carboy coupled with the sheer weight of it filled with fluid, makes it almost likely Also, the lack of handles on the larger vessels means that additional accessories are required to help with the handling. Check out this link for a list of horror stories.