Basic Glass Seals

7 Standard Glassblowing Operations

The following "courses" are not intended to introduce anyone how to blow glass. If you are trying to learn directly from this collection, you are facing an interesting challenge. Rather, this is intended to suppliment the glass taught during Fall Quarter at California State Univeristy, Los Angeles, Chem 316: Scientific Glassblowing. No matter how detailed this material could be written, they cannot compete with seeing someone perform these operations.

Simply put, glass is unforgiving. As opposed to woodworking where if you over-saw a piece of wood, you can always glue it together, use some putty, and still get it to function, if you make a mistake in glass you throw it away. Seldom can one correct a serious problem.

Another issue is that the longer you work on any seal, the worse the final result. If you are using the wrong flame size, or gas/air mixture, you are likely to work and work the seal. The most likely scenario when you overwork a seal is that you begin to involve more glass ito the seal and make things much more difficult for yourself.

Each step in any of these processes is dependant upon the previous step. If any step was poorly made, it only makes the subsequent step that much harder. Typically, the ability to overcome a previously poorly made step requires more experience than the person who makes the poorly made step has. And as one would expect, the experienced person is not likely to make the mistake that needs subsequent correction.

Thus, if you are new to glassblowing, you should not plan on working on the final piece unless you have practiced on scrap glass.

For practice, plan on working on glass pieces that are a good size. Each piece should be about 9-12 inches long (23-30 cm) as they provide sufficient glass to hold onto and will not be so big as to be unweildy. Glass tubing can come in lenghs of 4 feet or 1.5 meters (depending on the manufacturer). Nine inches (23 cm will give you 5 pieces per 4 ft length, and 12 inches (30 cm) will give you 4 pieces per 4 ft length.

Fire-cracking glass

There are many ways to break glass, this shows you how to break glass with a flaw and a flame. How it's done

The "Butt" seal, or stright seal

This is simply taking two tubes of glass of the same diameter and sealing them together. How it's done

The "Butt" seal with Capillary Tubing

Capillary tubing has a small ID with thick walls. They require special pre-treatment before sealing. If you are sealing capillary tubing to standard tubing, you still need to pre-treat the capillary half of the seal. How it's done

The Test Tube

While commercial test tubes are made by machine, not only is there the ocasional demand to make a test tube, a test tube is the 1st step in constructing the next item: the Uneven Seal. How it's done

The Uneven Seal

The uneven seal is simply joining two tubes who's diameters are not the same. This is a two-part operation where the first part is to take the larger of the two tubes and create a test tube bottom. The second part starts with this lesson. How it's done

The "T" Seal

As it's name implies, the "T" seal joins two tubes to form a "T" shape. How it's done

The "T" Seal with
Capillary Tubing

Just like the above "T" seal but with the extra complication that working with capillary tubing provides. How it's done