The Undercoat – The Big Benefits You Get

Not a teaspoonful!

Hello again. Thanks for coming over – always, the extra time you put in … it will serve you well.

So, the benefits of painting an undercoat before you trace …

First, the undercoat gives you a lovely (slightly rough) surface on which to trace. It actually improves your brush-control.

Second, it helps you build up depth of colour, layer by layer, in a steady way. Indeed, dark paint can be difficult to control, but now you don’t need to risk overloading your brush with dark paint, because the undercoat itself gives body and depth to the lines you subsequently trace on top of it.

Third, the undercoat protects your glass from airborne grease; it keeps it clean (bare glass gets dirty, and you can’t paint on dirty glass).

Fourth, it reminds you to handle the glass carefully at all times so as not to make it dirty or damage the work you’ve done already.

And fifth – after you’ve finished tracing and shading, you can take a stick or scrub and make highlights by cutting through the undercoat to the bare glass underneath. Do you see how astonishing this is? Most books say to trace, then fire, then apply a matt in which you make your highlights, then fire a second time. But with an undercoat, you fire once.

Exactly: paint better, fire less.

Now I’ll tell you one more astonishing thing.

Most books say to trace and fire, then do your shading afterwards, and fire again. Yes? Most books say you need several firings to trace and shade.

But listen to me here. And listen carefully because it’s important.

“Trace then fire; shade then fire; and so forth …” This is not how the ancient glass painters did their work. Firing was far more complicated, hazardous and expensive than it is for you or me today. Which means the ancients didn’t fire their glass more times than they needed to. And here’s the point: I know for a fact it was by means of the undercoat the ancients could trace and shade and do all their painting in just one firing.

Why is this important?

Just look at ancient painted glass.

Isn’t it beautiful?

And wouldn’t you like to learn to paint that well?

Paint better, fire less – yes, you need a lump of glass paint (not a teaspoonful), and after that, you need … the … undercoat!



P.S. Next time I’ll tell you the technique.

P.P.S. With all of this, don’t wait for me to tell you everything you want to know: have a go. Your own experiments will give birth to useful questions in your mind.


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14 thoughts on “The Undercoat – The Big Benefits You Get

  1. Well I was so excited to get the undercoat on my glass pieces and it looked really terrific. Tonight, when I went to trace the design, I couldn’t see it through the undercoat! I just got a lightbox—LED. Not sure if that has anything to do with it Probably a heavy hand wu\ith too much paint in the wash? Should I start over or look for a different lightbox?

  2. Hi Stephen,
    I’ve been reading your very interesting emails for awhile now and I just wanted to thank you for this freely given info you provide.
    Thanks again!
    Gary Hudson

    • Hello Gary,
      It’s a pleasure. David and I are gregarious and out-going, but we have so much work to do (this is not a grumble!) that writing this blog and exchanging ideas and thoughts with you and others – well, it’s a pleasant and stimulating break from the light-box.
      Thank you for your companionship and interest.

  3. Hi,
    Thank you for sharing all the tips you’ve learned by experience. I like to try everything but for the undercoat I did encounter the same problem as Virginia Heller, comment under. I made sure the coat was light but I can’t see my design on my lightbox ( regular 60 bulb).
    Maybe I missed something there! I will try again!

    • Hi Lucie,
      Getting the undercoat right is a bit like learning to ride a bicycle: it seems hard, but, once you get the hang of it, you can almost do it without thinking. Keep practicing and you’ll get there – I know you will.
      All the best,
      PS If you use the search box top right (beneath the picture) to search for “undercoat”, you’ll find a post with some more videos in it.

  4. Thank you for your tip about the undercoat, and about “landing” the other day, and for your generally encouraging, inspiring emailed tit-bits, Stephen. It’s helpful to get little bites at a time so I can read your email and then get on with my day.


    • Hi Emma – I’m glad you’re happy. And, as you rightly say, the thing is always to get on with one’s day – in our case: spending time with brushes. Best – Stephen

  5. I am a ceramic tile artist for 20 years. I also have painted on glass for several projects. After I do do my undercoat, I use an overhead projector instead of a light box to draw out my design. I use this to project designs on my tiles also. Just wanted too share this info.

    • Hello, John,
      In the abstract, I can’t be specific. So much depends on the passing light and also on the glass around.
      What I can say is, we often use an amber tint or a light green for the base glass for faces.
      Also, ourselves, we don’t shade the glass with specific paint e.g. red for flesh. But instead we mainly use our standard mix (3 parts black, 1 part brown) for lines and shadows, relying on the observer’s eye/brain to adjust what it sees so that it’s not seen literally but as a hand, a face etc.
      I hope this helps.
      P.S. By all means email me a photo if you wish, so I get a better grasp of what you mean when you say your hands and faces are too dark.