Sandblasted, cold worked, want to shine it up

[S.TImmerman]

I searched the board and could not find anything that would come up- there were a couple old threads but they would not show up. I have fused this once- cold-worked the edges and sandblasted both sides. Its 16.5" - largest piece I've ever made. I would like this to be shiny and wonder if it can be done during the slump? Do I need to refuse it to bring a shine? The edges are done- should I have waited to do the edges? Will they need to be redone if i re-fuse it?
Also, what would be a VERY conservative slump?

Many thanks !!

Sheree

[Brad Walker]

You can not shine the piece up during a normal slump. To do that, you'll need to fire to around 1375F. Slumping at normal slumping temps will just leave you a matte finish, not a shiny one. (I like the matte better than the shine, but that may not be your preference.)

If you want the edges to stay straight and not round, you can try firing to around 1350F and holding five or ten minutes. That shines them in my kilns without causing them to round, but kilns are different so you may want to test another piece first.

A conservative schedule for firing a two to three layer piece is to fire at 200F dph to 1100, then at 100F dph to whatever you top temperature needs to be. Anneal for one hour at your annealing temperature, then 100 dph until 50 degrees below the annealing range.

For example, I would conservatively slump the piece in your photo as follows:

200dph to 1100 hold 10 minutes
100 dph to 1200 hold 30 minutes (may be a bit less in that mold)
9999 to 900 hold one hour
100 dph to 750 kiln off

A fire polish would be the same, except a shorter hold at the top temperature of around 1350 to 1400, depending on how you want the edges to look.

[Eryc F.]

I love how that looks!!! Is it tacky and in poor form to ask how it's done?

[S.TImmerman]

Brad,

I really appreciate your concise and clear answer. Thinking about it more I agree that a matte finish would look better.

When its finished it will be the first time I'll post in the photos.

Thanks you!

Sheree

[Tony Smith]

During slumping, a sandblasted piece will take on a satin sheen. At 1175, for example, the sandblasted area loses its powdery appearance as though the sandblasted surface had been sealed. At 1200, there is even more shine to the satin. The look continues to change as the temperature is increased... at these low temperatures, temperature has a more drastic effect than time. but Brad is right, youll need to get the temperature above 1350 to get the surface to smooth out completely.

Tony

[Valerie Adams]

I love how that looks!!! Is it tacky and in poor form to ask how it's done?

One TINY, precise piece at a time!
It's a beautiful, technically challenging (to me) piece that I'd never in a million years have the patience to attempt.

[Eryc F.]

LOL That's actually the type of thing I have patience for and love doing - I may try something like it someday. I'll add it to my list of 4,523,265 things I want to do someday...

[Joe Lorenzino]

On some of my pieces, I used to "hand lap" the surface after sandblasting, but before final slump firing.
The plan was to refine the surface and edges down to a fine "matt" finish before the final firing, as it seemed they would shine up much better at slumping temperature than if they had been left in "as blasted" condition.
I used to use 280, then 400 or 600 loose grit on a wet sheet of plate glass for larger pieces, or the same grits in waterproof sandpaper stuck to a lapping plate for smaller pieces.
The task can also be done with diamond hand pads.
The objective is to get a "ground glass" finish similar to the viewing surface in and SLR film camera, before final slump firing.

A given amount of heat work may not level out the marks left from sandblasting, but it does have a much greater effect if the only marks are left by 600 grit.


I am amazed at the amount of cutting/fitting that must have gone into that piece.
Was it assembled with a clear top sheet for first firing?
How deep of a slump do you have in mind for it?

[lbailey]

Won't slumping (especially a moderate or deep slump) distort the wonderful geometry of the design ?