The Tale of the Stained Glass Designer and the Naked Scientist

"Not the BBC again!?!"

“Not the BBC again!?!”

What a headline! And it’s all true.

Question: does old glass sag at the bottom?

Here’s what happened …

David and I were working away, minding our own business, and finishing off the fourth set of brand-new windows that we’ve been making for a mansion on the shores of Lake Geneva, when the phone rang.

It was the BBC.


A top-notch producer wanted to know if old glass was thicker at the bottom.

The reason is, glass has a name for being a “super-cooled liquid” (just as Williams & Byrne has a reputation for being a super-cool stained glass design studio …)

"Are you telling me that my bottom's fat?"

“Are you telling me that my bottom’s fat and droopy? Grrrrrrrr!!!”

And many people think this fact explains why, when you look at old church windows, for example, you often see bits of glass which are thicker at the bottom and thinner at the top.

Their idea is that, over the centuries, the glass has dropped and sagged.

And this BBC producer was ringing us on behalf of Dr Chris Smith.

Dr Chris (as his friends call him) is the anchor-man for an excellent radio show, “The Naked Scientist”, which airs once a week.

(I suppose nakedness doesn’t matter when it’s radio.)

The show covers all the latest scientific breakthroughs.

So how, you might ask, does stained glass fit in?

Well, there’s one section called “Stuff and Non-Science” where they examine a common idea and find out whether or not it’s really true.

Health & Safety Rule #1 - Do NOT allow a Naked Scientist into your stained glass studio

Health & Safety Rule #1 – Do NOT allow a Naked Scientist into your stained glass studio

This week The Naked Scientist wanted to find out whether old stained glass really droops.

David and I don’t believe it does.

And here, courtesy of the BBC, are our reasons.

Be prepared: the telephone line is slightly rough. (After all, we are in the tranquil heart of the English countryside – wild and isolated territory that it is.)

You have two fine options.

You can skip to the best bit and just hear me.

Or you can learn all about horses, earthquakes and exomic sequencing and then come to the 20th second of the 22nd minute where … The Naked Scientist grapples with the Stained Glass Designer.

It’s your choice:

  1. Skip to the best bit and just hear me, which is right here.
  2. Download the whole show right here. (You can always fast-forward the 20th second of the 22nd minute.)

The full program was originally broadcast on 9th March 2009 and is copyright of the British Broadcasting Corporation.

Note this: if my voice sounds strange, just remember, it’s not every day that you get to talk with The Naked Scientist.

"Just let me get my hands on him!"

“Just let me get my hands on him!”


  1. Gloria Duerst says

    For a ray of bright sunshine just keep coming back to this blog: you guys are so funny. You just cannot beat British humor!

    I’m from Wisconsin … also thickening at the bottom.

    And it does seem to be with age.

    Hmm, this is a tough one.

  2. Martin Parsons says

    Perhaps you should now design a ‘Naked Scientist’ as part of your portfolio! I’m sure you could come up with some interesting interpretations!

  3. John Zappulla says

    Clear, concise, and to the point! What an excellent explanation. It dispelled my incorrect beliefs regarding the thickness of stained glass and why it would be placed at the bottom.

    I guess I am spoiled, working in today’s mass produced media.

    Thank you “Professore” Stephen :0)

  4. says

    Fascinating! These interveiws should be summarised – nay immortalised – in the form of a limerick. I would do it myself, but I can’t think what rhymes with “old stained glass”.

    Many thanks for this concise explanation. I must let my son know the truth, because he put me on the wrong track when he was a teenager and knew everything!

  5. Geoff Caldwell says

    I’m a glass beveler, and another myth is that beveled glass and sunlight can start a fire. Indeed years ago a court case in Texas was decided when a judge ruled that a beveled glass hanging had indeed caused a fire! Of course this is nonsense, the bevel produces a prismatic effect which separates the light into its wave lengths (colors), It is a lense concave or convex ( forget which) which focuses light enough to start fire. People have been asking me about the thickness question for yrs. I give them your answer, though I must confess that the part about came gap, cement, and less (no) water had not occured to me. Carry on glass men. Geoff C.

  6. says

    Hi Martin,

    A stained glass naked scientist – now there’s a coincidence.

    Mind you, the proposal is still in its very early days.

    Here it is.

    We have been approached to design a pair of lancet windows which depict some of the inexpressibly beautiful scientific truths and numerical relationships that underpin the evolution and operation of the Universe.

    This is for a church.

    The idea is that these great empirical and number-theoretical truths – not the traditional arguments for the existence of God – actually give us a special way of knowing of God’s existence.

    They reveal the Mind of God.

    So what I am saying is that we may yet design that stained glass Naked Scientist.

  7. says

    Hi John,

    I’m glad you found it clear.

    I think it’s so interesting how there are often several moreorless plausible explanations for a particular observable phenomenon – and then how one “explanation” takes the lead in the race, even though it may not be the correct one.

    Especially with the internet, ideas can spread like wild-fire.

    But of course that also means that true ideas can spread.

    So there are a great many benefits to be found in mass-produced media, provided one can scrutinize them adequately!

  8. says

    Hi Maurie,
    Thanks for your comment. I’m glad you enjoyed the interview.

    Yes, I also find it interesting how wrong ideas can all too easily become accepted as conventional wisdom. At which point it becomes difficult to challenge them.

    Another example – one which we are forever arguing against – is the idea that you cannot paint on top of unfired glass paint.

    We read it time and time again in glass painting books.

    And it’s just plain wrong.

    There’s a germ of truth in it, but not much more than that.

    The real truth is that it’s actually easy to paint layer upon layer of paint on top of earlier layers of unfired paint. It just needs to be done in a particular way!

    Thanks again for your comment.

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