Welcome,
I believe that education for anyone regarding lampworking or lampworked pieces is very important. This topic will discuss the details that anyone should know (or ask) about how a specific glass artist works, the glass making process and other details before you buy ANY HANDMADE GLASS PIECE. With the amount of inferior, non-durable glass flooding the market lately one should make sure that their piece has been created with specific methods. If these methods aren't clearly outlined or the artist will not answer your questions, then buyers beware!
I would like to begin by explaining the basics of the glass lampworking (flameworking) process:
Lampworkers’ take rods and tubes of clear and colored glass and heat this glass in a torch flame until molten. The two most common glasses used are Borosilicate (Hard Glass) and Effetre (Soft Glass). Borosilicate glass (Hard Glass) starts to melt at 800
0C or around 1500
0F. Effetre Glass (Soft Glass) starts to melt at 565
0C or around 1050
0F.
Then through a (sometimes very lengthy) process of using heat control (heating different parts of the work to different temperatures), blowing, tools, gravity and hand movements a piece of glass is made.
Next, we will discuss what information should be clearly displayed or should be quickly answered by the artist before buying the piece of glass.
Let’s start with the quality of the glass:
There are many glass companies where artisans can buy their glass rods from. As with any product quality can vary greatly by manufacturer. Lately there has been a lot of inferior made glass at a very cheap price. Specifically glass made in China and some other developing nations tend to be inferior. If you start with inferior glass, what you will get is an inferior product. The artist should have no problem telling you at least which country they get their glass from, and some will even tell you what manufacturer.
Now let’s talk about the artist:
Professional Glass Artists may vary from a beginner to apprentice to a master and everything in-between. Is an apprentice's work inferior quality to a master? That would depend on the particular apprentice and master. Under a watchful eye glass can be made of the highest quality from almost any level of glass artist. Apprentice work tends to cost less as their work may be less complicated and intricate than artists with more experience. Master glass artists can create pieces that leave you wondering how it was even possible to create. A professional glass artist should be able to answer almost any questions you may have about them. This means it very important that you can contact the particular artist of a piece of glass that you wish to purchase.
Recently there has been a lot of mass-produced glass posing as high quality artisan work at "rock bottom" prices. One would have to wonder who made this glass and with what quality of glass. In my experience if something seems too good to be true, it usually is.
Annealing:
“The process of slowly cooling a completed object in an auxiliary part of the glass furnace, or in a separate furnace. This is an integral part of glassmaking because if a hot glass object is allowed to cool too quickly, it will be highly strained by the time it reaches room temperature; indeed, it may break as it cools. Highly strained glasses break easily if subjected to mechanical or thermal shock.” (
cmog.org)
One of the most important processes in glassmaking annealing. Below is an article and a video from the Corning Museum of Glass (
comog.org). It is VERY important that you know your glass has gone directly from a hot torch or working environment into a HOT annealing kiln. In the video you will see how quickly glass can be “stressed” thus leaving the piece weak and able to fracture very easily. A properly annealed piece of glass should have no stress and should last more than a lifetime! NEVER buy a piece of glass that you aren’t 100% sure has been annealed. The piece could easily break and cause injury.
Annealing Glass
Annealing (wmv)
Annealing (m4v)
If a hot glass object is cooled "too quickly," it may be strained at room temperature, and therefore may break easily. For small, or thin-walled shapes (particularly those made of glasses having low expansions) the effect may not be serious. For more massive pieces, the strain can be very serious. The amount of strain (observed in a polariscope) depends upon how quickly the object passes through a critical temperature range. The range depends on the composition of the glass but is usually about 450°C. If the glass is cooled slowly through that range, so that the temperature near the surface is never very different from that of the interior, then the strain in the resulting object is much reduced. . Such glass is said to be
Annealed.
Glasses differ from crystalline solids in that glasses do not have distinct melting points. This difference is explained by the fact that the chemical bonds holding the atoms together in a regular crystalline structure are identical. When the crystalline solid is heated, all the bonds break at exactly the same temperature. Below this temperature, called the melting point, the material is solid; above the melting point the material is a liquid.
Conclusions:
To sum all this up, when buying glass make sure that:
1. You know where the original glass came from and that it is of the highest quality.
2. You can find out specific information about the artist.
3. The pieces are properly annealed.
If you have any questions, or believe I should add some more particular information contact me at
MACE@Maceglass.com.