Sue Sills wrote and asked us about mixing glass paint with white vinegar:
I have only used water and gum for mixing tracing paint so far.
But I was recently told that you can use white vinegar instead of water and that it stopped the paint from drying out so quickly, thus making it better for tracing lines.
Do you know if this is so?
The benefit of vinegar tracing
Now it’s certainly possible to mix glass paint with white vinegar, and trace with it onto stained glass.
But many books suggest a different virtue than stopping the paint from quickly drying out.
Here, for example, is Albinus Elskus:
When the finished [vinegar] tracing is drying out, the white vinegar will harden the paint and render it water-repellent.
This allows you to apply a coat of water-based matting color before firing in the tracing and so save one firing time” (The Art of Painting on Glass, Albinus Elskus, The Glass Press, 1980, p. 25)
So the received opinion on the virtue of vinegar-based tracing paint is that it allows you to trace and matt in just one firing.
We’ll return to this opinion in a moment.
For now, let’s just consider the question whether vinegar-based glass paint actually slows down the drying time.
In our experience, this is not the case.
Rather, what it does to is to increase the hardness of dried (unfired) glass paint.
It’s exactly this property which – as Elskus suggests – allows you to matt over it with water-based paint, and thus save yourself a firing.
A small difficulty with vinegar tracing
But you also need to know that dried vinegar-based tracing paint is far more difficult to reconstitute and re-use than dried water-based tracing paint.
This is the case even when you’re just working with a teaspoonful of glass paint (and not the 3 ounce lump that we definitely recommend when you use Reusche tracing paint mixed with water).
So it wouldn’t be a good idea to mix up anything more than a teaspoonful at a time.
In part-time conclusion: vinegar makes unfired glass paint more resistant to water, but it doesn’t decrease the speed with which paint dries.
I hope that answers the main point that Sue raised when she wrote to us.
The uses of vinegar tracing
Now let’s return to the question of water-based matting over unfired vinegar-based tracing.
And let’s be absolutely clear that this is a perfectly correct technique.
Therefore, if you’re restoring a broken piece of painted stained glass, and this is how the broken piece was originally made, then this is of course the technique that you should master and use.
And what about your own stained glass painting that you’ve designed yourself?
Here’s what we think.
If you wish to preserve an absolutely stark line – in other words, if this is what is demanded by your design – then, to save a firing, you can indeed use a vinegar-based mixture, and, once it’s dry, apply and work a water-based matt.
The vinegar hardens the trace so that you can blend the subsequent matt without softening or destroying the trace.
However, what you learn from our studio painting manual (free chapter here) is a different approach to line and shadow.
And, with this different approach, you also learn a different set of glass painting techniques.
Indeed, you learn how to throw received opinion on its head.
You learn how to shade and matt before you trace, and then, even before firing your water-based matting and tracing, you discover how to trace and matt with oil-based paint.
And then you get to fire your paint just once!
If it’s absolutely rigid lines you’re after, then, with our approach, you just trace them on with water-based paint once you’ve finished your water-based shading. (This is all covered in Part 3.)
And as you discover in various glass painting projects like the owls, you can also paint a water-based matt on the back of a piece of unfired glass painting.
Really, therefore, you can use water-based paint to trace and shade in a single firing and build up as much density of tone as you could possibly wish. (So we do wonder, what’s the point of vinegar?)
Water tracing vs. vinegar tracing
Now it’s not that one approach is absolutely superior to the other.
As we suggested earlier, it depends on the requirements of your design.
For our own part, we are uninspired by the starkness of line as found in so much stained glass painting – the very starkness that is preserved by vinegar-based tracing coupled with water-based matting.
Of course we accept that starkness of line is wonderful in the right place.
Just consider medieval stained glass faces, for example.
But the stark (unsoftened) tracing line is just one tracing technique amongst hundreds.
Starkness of line should not be represented (and even worshipped) as the way in which “stained glass tracing” is done.
And yet this is exactly what happens in stained glass studios and art colleges across the world.
This dogma then feeds back into the way in which stained glass designs are conceived and prepared.
So a pre-conception about (just one) stained glass painting technique then slowly but surely begins to limit the possibilities of the craft as a whole.
Really, though, stained glass designers should design with the building and the clients in mind, and only then (when the design has been agreed) remember, discover or invent an appropriate technique to use.
Stained glass painting techniques are merely means to an end.
Therefore their true purpose is to help the realization of a design and artistic vision.
But ignorance and secrecy often permit them to constrain the act of design – and this is such a pity.
That’s why we take care to explain the technique of “softened lines”, as we describe them – painted marks on glass which are half-way between starkness and shadow.
It’s simply another technique to add to your repertoire – even if received opinion says it can’t be done.
“But isn’t it Dangerous?”
With layer upon layer of unfired water-based glass paint (as you learn from us), there’s certainly a risk that, if your attention wanders, you can wreck the piece.
In that case you’ll need to start again.
But we find that this risk increases our attention.
We find it also increases the attention of people who learn to paint like this.
If you trace a line and then fix it in such a way that it’s difficult or impossible to shift it – either by using vinegar on the one hand or by firing it in the kiln on the other – then you can afford to be careless with your shading and highlighting.
And that’s a pity.
On the other hand, if you paint stained glass as we suggest, you’ll have the joy of knowing that each layer of unfired paint is still responsive to your every brush-stroke – right up to the moment that you put the glass in the kiln and flick the switch.
This calls for great skill and sensitivity, but since when is that a bad thing?