05/04 Boro Glass Burnishers for Keum-boo with Tisha Abrahamsen

Saturday, May 4, 2024 
10:00 am - 1:00 pm PDT 

Instructor: Tisha Abrahamsen

This class will teach jewelers who have never worked with borosilicate glass (boro) how to make their own glass burnishing tools to use for keum-boo (a process in which 24-karat gold foil is bonded to fine silver using heat and burnishing tools.)

You will learn the differences between soft glass and borosilicate glass, why you would choose boro over soft for this application, and the basics of working with boro glass using a rosebud torch head on a Smith Little Torch.

Tisha will show you how to make a variety of shapes of burnishing tools for keum-boo in a variety of sizes of ball ends, knife edge, and “the Zamboni” tool, as well as how to make your own custom tools to fit your style of work.

Demonstrations will include safety with glass and setting up an area to work with glass in the jewelry studio, the basics of the three forces to consider when working in glass (heat, gravity, and centrifugal force), and how those forces affect the movement of the glass.

You will learn how glass responds to various flame adjustments and how to repair your tool if it breaks.

Finally, Tisha will show you how to use a flex shaft and diamond discs to refine the shapes into the tool of your dreams. 

All levels

 All classes include the video recording, which you will have access to for 60 days after the class. Zoom link and instructions for joining the call will be emailed 1 day (24 hours) prior to class.

The class supply list is below, and contains links to buy the supplies you need.
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Supply List for Students

The links below will take you to RioGrande.com or other suppliers. To see prices for precious metal items, you need a free Rio Grande account. Students in the Rio for Schools program enjoy wholesale benefits for six months (instructor code = RFSLMF). This site may contain Amazon and other affiliate links. If you purchase something through the link, at no cost to you, we may receive a small commission on qualifying purchases.

Recommended materials:

• Borosilicate clear rod, 6–8 mm, 10 or more pieces Symax or Schott
• OR 6 mm Lab Stirring Rod 12"
• OR 10PK Glass Stirring Rods, 7.9" - Spade & Button Ends, 6mm NOTE: you will probably have to join two of these shorter rods to make one burnisher

 Recommended Tools:

• Smith Little Torch, or the equivalent propane/oxygen or acetylene/oxygen torch
• Pana Vise, or a way to hold the torch for hands-free use.
• Didymium glasses or clip-ons - these protect your eyes from sodium flares and are A MUST!
• Rosebud torch tip for propane/natural gas
• OR Rosebud torch tip for acetylene or hydrogen
• Soft fire brick
• Hand-held torch striker
• Steel bench block
• Chasing hammer
• Steel long tweezers
• Inexpensive medium file
• Small tin can with a bit of sand at the bottom
• Glass cleaner - alcohol-based, vinegar-based, or ammonia-free. NO Windex or ammonia-containing cleaners. It will leave a residue on the glass.
• Towel. Paper or cloth, preferably lint-free.
• Pencil and paper for sketching and note-taking
• Newspaper or a paper towel under the glass to catch shards and splinters created by scoring and breaking.

Optional Additional Materials and Tools (nice to have but not essential):

• Graphite paddle
• Glass rod rest
• Tweezer mashers
• Set of diamond cutting wheels
• Small plastic crayon box
• Kitchen sponges
• Flex shaft
• Flex shaft holder