Answered By: Beth Hylen Last Updated: Jan 13, 2017 Views: 132
To fuse two COE 90 glass pieces, both must be evenly hot.
Heating just the bottom of the bowl and top of the base would create a great deal of stress between the hot area and the cold area. The piece would probably break before it was placed in the annealer.
Have you watched furnace workers joining two pieces? One piece is "garaged" in a warm kiln while they work on a second piece (i.e. joining a cup and foot of a goblet). That is how they avoid shocking the glass. (I attached a description of a garage used for furnace work from Henry Halem's Glass Notes; however, many glassblowers use a kiln for this purpose.) This would be difficult with fused glass, especially if your pieces are large and thick.
Flameworkers using borosilicate glass have a little more leeway because the COE is lower, but they often use the "garage" technique when joining two pieces.
Consider joining your pieces with adhesive. Here is a link to our "coldworking" guide: http://cmog.v1.libguides.com/cold
Adhesives are often used to attach fused pieces. Milon Townsend wrote several articles about different types of adhesives (listed in our guide).
If you wish to obtain copies of library items, please contact your local library. The Rakow Research Library is a member of the Online Computer Library Center (OCLC). Your library can contact us through OCLC or they may send an Interlibrary Loan form to us by e-mail. We send copies of articles and will also loan certain books if a second copy is available in the library collection. Books are loaned for a four week period. For further information, please see our web page: http://www.cmog.org/research/library/visit/services/loan.
Please contact me again if you have further questions.