kiln carving

[chas]

We’re trying (and we don’t mind experimenting) to create a piece from float that has a 3mm ‘indent’ but have yet to find the right combination of top temp/hold/glass thickness to eliminate the usual tell-tale relief on the top side - we’d like it flat.
The very useful Bullseye Tipsheet I found in t’archives https://www.bullseyeglass.com/methods-ideas/tipsheet-1-kilncarving.html
ends at a stage 3 with a tantalising “ at 825/30mins the surface begins to level out...” suggesting higher temperature and/or longer hold and real flatness might be achieved.

Anyone done that? If it was in Bullseye, it would still give us a steer for float...

 Chas

[Zeldazog]

Hi Chas

Not exactly sure what you're asking, but I do kiln carving with Bullseye and got pretty flat with a normal full fuse - I can't say that it was absolutely perfect, but not far off, and I'm sure a bit longer hold/slightly higher temp would solve it.  I've never needed to go to 825degC, but then again, I wasn't looking for absolute flatness

What I would say is that I kilncarve and usually get reasonably flat results with Bullseye at my kiln's standard full fuse.  But, when I kiln carve with greenhouse or float glass, and *that* standard full fuse, I usually get a bumpier finish.

in both cases, I usually work to 6mm

Given that all kilns are different, I think you probably will have to do that experimenting to find the magic numbers for your kiln.  I don't know if you usually work with float, but I full fuse at around 840.

[chas]

Thanks Dawn, and first some clarification: we’re wanting to make from 6mm float, get a 3mm ‘carve’ and a flat top. Really flat.

We’re currently working at 840/30mins (Nabertherm - of course kilns vary, and our 840 may not be your 840) and so far have good carved relief but a corresponding raised area on top. In effect the glass is draping over the former and staying ‘proud’ except around the edges. We would really like to flatten that out!

As I say, we rather like experimenting, but wondered if it’s a hopeless quest. Anyone solved it?

Chas

[Zeldazog]

As I said, I've got pretty much flat (flat enough for a long stemmed wine glass not to topple over!) with 6mm bullseye on full fuse (it may have been a higher full fuse than I do now, as it was early days - but certainly not 20 degrees over) but I don't get it flat with window glass.

Given that Bullseye recommend going 20 degrees or so over a normal fuse to start getting flatness, I think you've got to look at going  at least 20 degrees over on your float as well.  Float does generally seem to be a bit stiffer than art glass, but it's got to get fully molten at some point....