Your Undercoat: the Fifth Benefit

There are various reasons you must consider if your glass will benefit from an undercoat before you start to trace. 

Do you remember what these reasons are?

We’ll cover them in just a moment.

And – looking ahead – will it surprise you when I tell you how the undercoat also helps your viewers’ eyes?

Therefore, unless you are painting only for yourself – which might sound luxurious to start with, but actually it’s a mixed blessing because a demanding client can improve your work no end – this is something you definitely must know.

A quick reminder

Forgive the quick reminder, but we must agree on how we use our words:

The “undercoat” is a light-coloured wash of glass paint which you apply to the whole surface of the glass before you start to trace etc.

You apply this wash, and, while the paint is wet, you blend it till it’s smooth. Then, when the undercoat dry, you start to work on top of it with lines and shadows.

The familiar reasons are:

  1. The undercoat is a much more practical surface on which to trace than bare and slippery glass;
  2. It proves to you your glass is absolutely free from grease and dirt;
  3. It also keeps your glass clean while you work, and it reminds you to hold it at the edges;
  4. Later, when you’ve traced and shaded, you can use sticks and scrubs to make highlights – all this before you’ve even done your first firing …

That’s the summary.

And, when you want to know more, this foundation course Illuminate! has everything you need inside it.  

Now consider the next important reason why, each time you plan a piece, you must decide about the undercoat.

You see, all those reasons are to do with you, the glass painter.

And now it’s time to think about your audience.

The undercoat and who your glass is for

Yes, the undercoat helps you, but it isn’t just for you.

Fact is, the undercoat improves the legibility of your lines and shadows.

The undercoat makes it easier for your viewer to see and understand them.

The reason is, you’re working with transmitted light, which dazzles.

At the extreme, when the light is very bright indeed, we scrunch and close our eyes.

Think: driving at night when the oncoming car forgets to dip its headlights …

Certainly, it’s far less extreme in daylight where your glass is normally seen. But the same principle applies. The transmitted light can easily dominate your work.

The tragedy is, unless the problem is severe, it’s not something you will notice until it’s too late.

Do you know why?

Problem is, you’re too familiar with what you’ve made. Therefore your brain assists you, and everything seems clear to you.

But to your viewers’ eyes it isn’t.

Yes. Light dazzles.

Uncontrolled, it pours around your lines and shadows and squeezes in on them, making them appear thinner than you intended.

Which means your viewers don’t see the lines and shadows as you see them (because you know them all to well).

So I know how some people resist the undercoat because they feel it detracts from the very qualities which attract us all to glass – the fact glass is so bright and colourful.

But that’s the medium in its ‘natural’ state.

It’s only what you start with, your blank canvas.


And if you want your painted image to be seen as you intend, you may well need to assert control over the quantity of light which passes through your finished window.

The undercoat can help you there.

Make sense?

Therefore, is it right to call this the fifth benefit?

Actually, don’t you consider it is – the first?



2 thoughts on “Your Undercoat: the Fifth Benefit

  1. Really useful: thank you. I still can’t get over how the techniques which you guys prove are ‘fundamental’ don’t even get a mention in other books I’ve studied … Oh well: I’m glad I found you!

    • Different painters, different techniques: like you, I study them all, Henry. But I think one big thing which makes a difference is, everything we write about and film is based on getting things done as well as we can and as efficiently as we can. There’s just too much going on here; the techniques must work well, which also means they must work (or else they’re out). I’m glad you’re happy. As I know you know, the other techniques are just as successful.

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