Slumping Bottles Vertically

Today’s article was sparked by a question from a reader:

“Have you ever slumped a bottle vertically in the kiln, I want to achieve an artistic slump rather than a melted pile.  I figured if anyone had tried it it would be you.  Thanks, Andy”

Oddly enough, I hadn’t ever tried it, so I thought I would give it a go.

First I measured how deep my kiln is, this helps tell me how tall my bottles can be.

It looks like I have 9.5″ of kiln height.  I’m measuring from the shelf to the top rim of the kiln.  BUT, I have a very old kiln, and the elements do extend down into the kiln space.

So, I’d better subtract 1.5″ for element clearance, giving me a total height of 8″.  Now, how tall are my bottles:

I’ve selected two small bottles, one airline size Bombay Sapphire and one baby food jar, I’d like to see what a taller,  narrow bottle does, and a lower, wider bottle.  I also needed bottles that I had identical multiples of.  I’m firing these using my standard firing schedules so I know where to start, rather than just choosing a random temperature.

So, here we go, these two are fired using a full fuse schedule:

Next up is a Tack Fuse Firing Schedule (100 degrees lower than a full fuse):

And these two at a Slump Firing Schedule:

Here are the bottles next to each other so you can see the progress:

Things I learned:

  • Bottles aren’t an even thickness all the way around or top to bottom
  • The thin parts bulge out and slump first
  • Bottles don’t slump straight down (see previous)
  • Wider, shorter bottles are more predictable
  • The ideal slumping temperature seems to be somewhere between a slump and a tack fuse (about 1400)

Reader additions:

Hi Jodi – I tried this with a green beer bottle.  Thankfully, I was checking it because it went sideways and

hit the side coils.  I was able to remove it before any harm was done.  -Connie

EDITED TO ADD:  Based on Connie’s feedback, I’ve since taken to doing this process inside of a straight walled terra cotta plant pot that has been thoroughly kiln washed.  Keeps the bottle mostly straight upright during slumping, as well as protecting my kiln sidewalls.  (no photo though, sadly)

If you try this and like your results, please let me know!

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