“I've cut wine bottles horizontally and want to keep the boat shape but round the cut edges. [Will a tack fuse firing] do what I am wanting without changing the shape of the bottle? “
Temperatures
The softening point of bottle glass is around 720˚C. The
temperature you have chosen for a fire polish is 730˚C. It will slump to some
degree from about 700˚C. That will not
be high enough to fire polish the edges.
Reducing the soak time at 730˚C will reduce the slumping effect a
little, but it will not polish or round the edges.
Ground edges
In addition, ground or sawn
edges are so rough that fire polishing will not work well at any temperature, because
the rough surface promotes devitrification.
To get a good fire polish, the edges should be ground to at least 400
grit, and 600 grit gives a more certain fire polishing result.
Cold Working
Fire polishing is not the most certain way to round and polish edges for
a 3D object. Cold working with hand pads or grit is the low cost way to polish
the edges. The grinding will need to go
through grits of 200, 400, and then smoothing pads and finally pumice or
cerium oxide depending on the shine wanted on the edges. This can be done by hand or by machine. Paul Tarlow has an excellent eBook on cold working by
hand, and there is some instruction in this blog.
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