Most People Get Their Blending Wrong ...

They hit the glass too hard

Right, in his last post, Stephen challenged you to do it with one hand tied behind your back.

Undercoating, I mean.

And several people wrote how maybe they were heavy-handed, because no matter how they tried, their glass always spun away across the light-box.

So I reckon the best thing now is to show you what we mean.

Sounds good to you?

Good, so let’s get going.

Undercoats are great because …

OK, if you missed Stephen’s earlier post, please see it here – it explains the big benefits of undercoating your glass before you trace and shade it.

Stained glass painting - the undercoat

The undercoat

That’s why a light touch is best

And Stephen’s point was, it’s virtually hands-free – you generally don’t need to hold the glass you’re painting.

This is important because a light touch will give you a gentle, even undercoat.

OK so maybe that’s easier said than done.

Which is why I dug through our video archives and spliced these clips together for you here. Please note: I’m not showing you how to mix your paint or load your brush or anything like that right now. All I want to do is show you how to move your brush across the surface of the glass, and also how to blend your paint.

So turn on your volume and have a look at this, why don’t you …

Thing is, undercoats are so useful, they’re absolutely worth practicing until you get them right.

And now you know: the best test of doing them right is … you barely need to hold the glass.

Happy glass painting!


P.S. Learn more about undercoats, get the full guide: find the full guide here.

23 thoughts on “Undercoats

  1. Hello David,

    Thank you for this useful information. Frankly speaking, since I started the undercoat method in my glass painting, I notice that I am more able to do my line tracing and that I can control how dark the glass I am painting is, and many other things besides! I for one am sure I will not be able to do all these things without painting an undercoat.

    Regards to you and Stephen and both your families!

  2. Hello David:

    I noticed on quite a few of those pieces you started coating it and then felt compelled to get your finger in there to rub the surface of the glass. What was that about? I can only think it was some water beading at the edge, but I would of thought oil from your fingers would make the problem worse. Do tell!


    Jason H.

    • Hello Jason,

      The glass was a tiny bit dirty to start with. There was a whole batch I’d prepared the previous day and I should have undercoated them the previous day but I didn’t … so the next morning, grease had “got to” some of them.

      And yes, you might expect my hands to be greasy, but after painting for a while, they’re actually quite abrasive!

      All the best,

  3. When you get your finger in there to rub surface of the glass, are you cleaning oil away maybe?

    Thank you, David and Stephen, for your mails. (I write to you from Lima, Peru.)


    • Hi Julio in Lima!

      Yes, I rubbed the glass with my very dirty fingers in order to remove some grease I should have removed before.

      I am happy for you and everyone to see me “spot-cleaning” the glass like this because it’s good for people to know how you sometimes have to push through a job and the obstacles it throws up. So if the undercoat doesn’t go on as smoothly as I might wish, I just go over it a second time – “good enough” is, yes, good enough – then blend it carefully until it’s … good enough.

      Of course it all depends on what is coming next. With all of these pieces, there will be a lot of tracing, shading, highlighting and painting with oil. So I can afford to be a little bit “rough and ready” with the undercoat.

      All the best,

  4. A bit of “Contact” paper or similar adhesive shelf liner can be used to hold small pieces. Cut a bit off the roll, remove the backing paper and place sticky side up on your light table. You can tape it down to the light table with a couple of pieces of masking tape. It should be tacky enough to hold the small pieces whilst undercoating, yet release easily with no adhesive residue on the underside of the glass.

    • Thanks, Robert – that’s a good tip. (I sometimes use children’s modelling clay myself.) Here, I just had two small pieces, so I was happy to fiddle with my fingers (as you saw). But you’re absolutely right – any more pieces than that, and it would definitely be a helpful idea to use tape or clay to hold them down.

  5. So If I want to acquire a copy of your book shown on the web page “GLASS PAINTING TECHNIQUES AND SECRETS”: how do I go about doing so?

  6. Thank you. Pictures speak louder than words. Can I paint a blue undercoat on blue glass? Is that what you did here or did you still use earthtones

  7. Hello!

    Once again, you’ve done it! I now follow you in your teaching and I improve every day: thank you!

    A question for you: when tracing with a quill, do I still have to paint an undercoat too? Please let me know. I have tried, and so far I always get mixed results: sometimes it works and other times I get double lines.

    As always, I thank you for your help.
    Philippe G Tillay

    • Hello Philippe,

      Good question because it lets me emphasise that undercoats are not obligatory. In fact the only rule is always: do whatever it takes (so long as it’s legal) which gets you the results you want.

      So, in our own experience, when someone wishes to paint with a tracing brush, an undercoat is very useful. It’s a rough surface which helps give your brush some grip.

      But a brush is soft. And a quill is hard. Therefore, I can well imagine that maybe undercoat and quill don’t go together. Just as undercoat and nib or mapping pen don’t go together.

      Therefore, unless you can consistently get the results you want – no double lines – I myself would only use undercoats when I planned to trace and shade with brushes.

      All the best,

  8. Great video of undercoats! I enjoy every single article and all your photos. I’m learning so much: thank you – you guys are the best of the best. I’m so glad to be your student. Some day I will fly from PUERTO RICO and meet you and learn even more. Happy holidays and have a great, prosperous year in 2013!

  9. Hello David,

    First off, thank you both for your fabulous contribution to the glass painter’s community. You make me feel less “alone” with my questions, because where I am, there are not a lot of people that have your expertise and insight!

    My question about undercoating: (I feel silly asking this) – Do you actually need to FIRE your undercoat before starting to trace, or do you simply let your undercoat air-dry, then move on to the tracing?

    Maybe I missed something …

    Merci beaucoup!


    • Hello Anne,

      Thanks for your question. It’s a good one, even though the answer is quick to state.

      You don’t fire your undercoat before you trace etc.

      You simply paint it and let it dry.

      Then, when it’s dry, you continue with copy-tracing, strengthening, shading / softening, highlighting, working with oil or propylene glycol etc.

      And to be clear: an undercoat isn’t necessary.

      We just know that, in many situations, in makes perfect sense.

      (Nearly all our work requires an undercoat: that’s how useful it is.)

      Always ask questions whenever you have them.

      All the best,

      P.S. You mention about working together/not working alone. That’s also how it is for us. The point about this website is not to talk about the projects we do in our studio. The point is for us and whoever wants to join in to talk together about techniques in actual daily use.

  10. Es uno de los videos que reafirman la confianza de uno de los temas
    basicos de la pintura en vidrio como es el “undercoat”, para seguir avanzando en esta tecnica. Muy util. Gracias!

  11. Hi David and Stephen,

    When I try to undercoat I don’t seem to get an even coat. It is lighter at the edges. Do you think there is too much water or the paint is not mixed well enough?

    I miss all the English accents from the AGG conference! And also both of your humor!

    All the best,

    Sue Nowak

    • Hi Sue,

      Miss you too!

      English accents I can live without; what I miss is American confidence, resilience, cheerfulness and spirit.

      So I must make do – for now – with a question from an American friend and colleague …

      A question whose answer I am not completely sure about. You see, it sometimes happens to me. In fact it happened to me yesterday; rather, I saw it was happening – so, yesterday, I just kept blending (my undercoat was still wet enough for me to do so), and focussed on the edges, using just the tips of my badger hairs, moving around so I addressed all sides.

      But this is not a methodical answer, just a coincidental one. In the past, when I’ve seen it happen, it hasn’t bothered me, because – with everything else that will happen: tracing, strengthening, shading, highlighting, other media etc. – my thought was: it’ll never show.

      Like I said: not a methodical answer.

      Thinking on my feet right now, I suspect it’s likely to relate to the consistency of the paint.

      So I’ll do some tests later this week and write back.

      All the best,

      • OK, so David and I talked about this, and both of us did some tests, and both of us reckon it’s a lot to do with the consistency of the paint: as dry as possible. So it almost – almost – sets the moment you apply it to the glass. “Set” doesn’t mean it dries: no, you can still blend it. But it doesn’t move by itself: that’s what “sets” means here. It stays where you put it. And then of course you tidy things up as needed with your badger blender.

        Couple of follow-on points …

        Also important to check your hake. It must just be damp before you start. Not wet with water.

        Your hake must also be evenly and entirely loaded with paint. So it can’t have water up by the shaft, then paint just down by the tips. It needs the same paint throughout.

        And you just lay it down with not much more than the tips of your hake.

        So, yes, you load the whole brush, pushing down hard on both sides, so it’s evenly and entirely loaded with this “dry” (not watery) consistency of paint; then you apply it with little more than the hake’s tips. It should settle where you lay it: no watery movement. And then you leap in quickly with your badger and kick the hell out of it till it’s nice and smooth.

        I do say “kick the hell”. Because it’s a funny thing … The paint can indeed be settled. But, provided you blend with your badger’s tips, and provided you blend horizontally (not in an arc, which always creates uneven pressure), you can still blend really vigorously and make the paint move around a lot – even though it was “set” when you used your hake to deposit it there.

  12. The badger is the ‘go-to’ brush for blending. Is it the stiffness/lack of stiffness, the length of the bristles (are they long or short) or other characteristics that make it THE brush for blending? I ask because I have one and use it for gold. I would never use it for undercoat, too. So I thought perhaps any good brush, but then thought I wonder what makes the badger such a good choice. Perhaps one of my other brushes would work well, too. Thank you, from a beginner.

    • For this kind of blending, it’s a combination of factors.

      So: the softness plus the length (about 3.5 inches) plus the width (about 3 inches along the base) plus the density (how many hairs there are).

      Myself, I wouldn’t use a different brush, but of course it’s possible you may happen to have one which works well for you.

  13. Hi Stephen,

    You have taught me the benefits of the undercoat, and I now wouldn’t dream of painting without one.

    I clean the glass using the paint. But on some glass recently, I have cleaned it over and over – and the paint still ‘separated’ when I tried to put on the undercoat.

    Was this because I don’t have enough gum Arabic in the paint?

    When your ‘ lump’ lasts you a long time, I wondered if, as you moisten it again when you remix it to the right consistency, I wondered if perhaps I have diluted the gum element? Or is there some other reason?

    Thank you for your site, your generous help and patience.

    • Hi Colleen,

      If the glass is clean and the undercoat continues to separate, then what’s probably happening is: the surface tension of your paint isn’t strong enough to bind your paint together until it dries.

      Which means the most likely causes are: your undercoat is too wet, and/or there’s not enough pigment in it.

      Too wet: most times the undercoat should go on quite dryly. (Yes, this is easier in England than in many other countries, because we rarely get hot weather.) So the undercoat is just wet enough for a little blending and no more. It goes on as a thin layer: that’s why I prefer to call it an “undercoat” and not a “wash”, because “wash” can mislead people into loading too much paint on their brush, and applying too much. So those are the things to check: see if you can load less (making sure your brush is just damp, not wet, to start with), and applying just a thin layer.

      Not enough pigment: glass paint thickens water, makes it more viscous (sluggish, sticky). Now, especially when people want a light undercoat, the tendency often is to make the undercoat more watery than it can bear to be. But this is the wrong variable to focus on: beyond a certain point of watery-ness, the paint just can’t hold together as an undercoat. There needs to be a minimum amount of pigment to the quantity of water. So, even if this darkens the undercoat, you must take some paint from your lump and mix it thoroughly with the undercoating reservoir: usually it just takes a little, so don’t go overboard! Then just follow the earlier points: make sure your brush isn’t wet, make sure you don’t load too much, and apply lightly,


Comments are closed.