Morganica wrote:I'm not entirely clear what you were trying to do? What was the end result supposed to be?
Emily Speight wrote:holes like this are either a volume issue or an air escape issue. .....................So yeah - make sure the mold holes are clear, make sure the mold is elevated, pre fuse a solid blank - and see if that doesn't fix your problems.
Emily Speight wrote:So yeah, in this case probably not annealing long enough. I think there's too much going on with the whole mold & texture imprint thing to anneal for only 45 min. Plus, the bottom got pretty thin, which would add stress.
It is unfortunate that there are two threads about Delphi molds and similar projects on the board at the moment. With all the variables associated with fusing, it is impossible to conclude what happened in these two instances as Delphi undoubtedly tested their products and projects extensively to work when all things are equal. I have a feeling all things are not equal in these attempts to use the products which is to be expected given kiln and glass variables. Since both projects appear to be using fracture/streamer glass and frit, it might be an expensive learning experience.
My first impression is that these projects are rather advanced as the following issues are present:
(1) glass volume;
(2) project element expansion;
(3) additional, non-typical stress;
(4) variable glass thickness.
(1) As Emily noted, glass volume can be an issue in these projects; assuming that the air holes are clear, this is probably the reason there are gaping holes in both projects. Bullseye's 'Kilnformed-Container' lesson
http://www.bullseyeglass.com/education/ ... r-164.html is similar to this project as relates to air escaping.
(2) While only one of these projects used the impression mold lying on top of the glass, the impression mold affects expansion both in the mold itself and glass shielded from heat by the impression mold. The heating, annealing and cooling phases of the firing schedule may be impacted. Graham Stone in his book, 'Firing Schedules for Glass,' suggests adjusting the firing schedule to a schedule for thicker glass to compensate for this issue; Bullseye's thick slab annealing chart
http://www.bullseyeglass.com/images/sto ... _slabs.pdf is a good resource for developing the annealing portion of the firing schedule; the .75-inch schedule would be minimal for these projects IMHO.
(3) Related to item (2), the impression mold adds stress by creating the potential for uneven heating/cooling of the underlying glass. The project is prone to break due to this stress in either the heating, annealing, or cooling phases (see annealing comments in (2)).
(4) Proper annealing is essential when uneven glass/mold thickness is introduced as the project temperature must remain fairly constant across the entire project to avoid breakage (see annealing comments in (2)).
Most if not all of these issues are addressed in Brad Walker's book, 'Contemporary Fused Glass,'
http://www.warmglass.org/books. This book steps the learner through a series of increasingly complex projects and is a great reference.