Things to Learn – or Re-learn – on the Way to SOFA | Bullseye Glass Co. | Bullseye Glass Co

Things to Learn – or Re-learn – on the Way to SOFA

Just when we thought we were pretty smart, we learned another kiln-glass lesson. It’s a corollary to Lesson No. 1, which is: NEVER think you know what’s going to happen in the kiln.


In fact, we sooooo know that we don’t know, that we always test before doing major projects.

For instance, we’d never fire up over 150 pounds of sheet glass without first test-firing a sample stack. This particular sample for this particular project – a SOFA-bound 3″ thick glass bench – was composed of strips of Opaline White intermixed with clear in an internal stepped pattern.

If you’re not familiar with Opaline White (aka 000403), I blogged about it earlier this year here and here.

Opaline is a fascinating glass that fires from clear in the cold sheet to a misty white at full fusing temperature. The glass is very time and temperature sensitive, the white becoming increasingly dense the longer it fires and the higher the temperature it’s taken to.

So, of course, we fired our test stack using exactly the same firing cycle we intended to use in the final project. We were also careful to select all the sample glass from the same production run that we’d use for the final project.

We liked the results, so we fired the two final benches.

Only we didn’t fire them in the same kiln used to fire the tests.

And we didn’t consider the effect of the increased mass – a major heat sink – on the rate of heating and cooling. The sample stack weighed about 20 lbs. The two benches together weighed over 230 lbs. That’s 10 times the volume of glass in our finished firing versus our test.


The white in the finished bench slab was noticeably more opaque. The Opaline had opacified considerably more than the same glass used in the test block – clear evidence that despite the firing programs and glass styles being identical, the firings were NOT equivalent.

A fundamental lesson: what you program isn’t always what you get. Never be fooled into believing that your controller is totally in control. The glass is in control. Always.

The resulting bench was just different enough from the sample – i.e. denser than we wanted – that we considered both benches rejects and had to remake the entire project.

Thanks to a major hustle by the studio team, the benches were remade in record time and are being loaded onto our SOFA truck tomorrow. Come by and sit on them in booth 607.

If you’re like me, they’ll make you feel really stupid.

3.BenchThe upside: this is a reject. You’ll need to come to SOFA to see the heroes.

8 Responses to Things to Learn – or Re-learn – on the Way to SOFA

  1. Bert Weiss says:

    One person’s reject is another’s treasure.

    The problem with your conclusion is that it requires a full sized test. No rest for the wicked.

  2. jenn houser says:

    The rejects are stunning! Would love to see the winner but flying to Chicago to sit on a bench is a tiny touch outside of my budget this year. Hope you post pictures of the final version.

    Enjoy SOFA!

  3. So, if the rejects need a home I’ve got a back deck just dying for a little touch of glass…

    Yep. I love opaline for many things and one of them is the way it surprises you. The whole heat sink thing gets interesting in both directions–been firing very small sculptures lately (pendants, really). I find that anytime I change the glass mass by a factor of 10 or more, everything changes and I’m in serious danger of overfiring unless I modify the schedules to take the almost non-existent heat retention of the glass (and the mold) into account.

    The rejects, as Jenn says, are stunning, though. And the whole architectural design thing is an inspired idea.


  4. So, just how do you make something that thick in “record time”?

  5. Lani says:

    Cut fast, fire slow.

  6. OHHH HOWWW BEAUTIFUL!!! Simplistic and just stunning.
    To dream of a kiln large enough to do that !!!!!!! (but of course all those amazing bullseye technicians tooooo! ) (and Multiple-Point Measuring Systems) (and don’t forget those amazing tools you have to get the glass out once it is made ) and oh yes, that amazing grinding / coldworking studio that is state of the art!!!! to create the art.. I will not sleep tonight!!
    I tooo am playing with the Opaline and it is such an amazing glass: tempermental like my personality. Now if I can just figure out how to control my own mood swings. !!and earn myself a new kiln so I can also enjoy experimenting on a large scale.
    Wish so badly I could fly down to SOFA so I too could have a seat on that bench and have a good conversation about glass with all the guests who will be in awe at your booth..
    Have a wonderful show . It is going to be so very interesting this year with your very amazing theme Lani. I can hardly waite to read the next blog.

  7. Hi Lani,
    Sat in a fabulous lecture today and heard about another exciting piece that’s going to be at SOFA!
    I’m so excited that I’ll be in Chicago a week today.
    I think that the Bullseye booth is going to create even more of a buzz of excitement this year.

  8. Lani says:

    So they made it to Wolverhampton! Yea! Looking forward to seeing you in Chi-town next week!!!

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