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Hello ! hope we all enjoyed our Christmas and New Year vacation....
I am in the process of making a cone shaped fused glass vase 10 inches long. I have tried to produce long vases before by sagging 3 circles of glass (thickness 4 mm) over a positive mold I made myself. After fusing I found that the glass accumulated at the bottom and became too thick . Sometimes there were holes were the glass became too thin (near the top). What went wrong? I would appreciate your advice and tips on oversized vases.

What firing schedule did you use?

Any reason why you're sagging over a mold instead of slumping or dropping into one?

Hi Brad

This is my firing schedule:
Celsius
150/h to 400 – 10 min
200/h to 620 – 20 min
Full speed to 780 – 10 min
In Fehrenheit:
300/h to 752 – 10 min
390/h to 1150 – 20 min
Full speed to 1436 –10 min

it is the firing schedule I normally use for fusing bowls.

There are several reasons why I am sagging over a mold instead of slumping : 1) the diameter of the vase at its largest part is only 6 inches 2) I don't want the glass to touch the mold so I can preserve the brilliance 3) to keep the natural edges of the glass after fusing.

The glass I am using is Saint Gobin glass but I can easily use clear spectrum glass if the expected results are better.

I used to make vases like you are describing on a commercial basis.
I probably made over a thousand of them in my previous studio.

You will not be successful to not have the vase touch the mold and to still create the perfect cone shape.
You have many issues to create the perfect cone shaped vase as you are rapidly discovering.

When I was making these vases the one thing I still chuckle about is that I made process notes about everything I did in the studio but not for the vases.
After I lost that studio in a D they were unable to make them.

Seems like it should be easy, but it isn't.

Hi Kevin
So you are suggesting to slump the glass inside a mold. In this case I would need 8 to 10 sheets of 3mm glass. A rule of thumb is that you need 2 sheets of 3mm glass for every 1 inch . If you have any other suggestions (based on your notes ) I am curious to know them.

In Fehrenheit:
300/h to 752 – 10 min
390/h to 1150 – 20 min
Full speed to 1436 –10 min

If I am reading this correctly, you are slumping/draping at 1436 deg F? That would be why you have holes and thickness in areas where you don't want it. Maybe I'm misunderstanding something...

Dana W.

Hello ! there is no misunderstanding. 1436 is the final temperature necessary for a full fuse of Saint Gobain glass. Maybe this is one of the reasons why the project was not so successful in my early experiments.

No, I used the outside of the mold, not the inside when I was making mine.

Are you trying to fuse and drape in a single firing? I've had some success doing this with float but not softer glass. I'd fuse the blank then slump/drape at a lower temp

Hi Fiona, hope all is well dear
Yes, I tried to do everything in one firing, but as you said, I will have to fuse, then slump. I have seen very long pieces achieved in one firing at the Glass Art museum in Cairo (where I learned fusing) , but the mold had very deep sculptured lines which prevented the glass from slipping too quick over the mold. I am sure they also applied a lower speed towards the end of the firing schedule but these are masterpieces produced long ago with Russian glass.