Verdigris Dive

Painting “Bubbles II” – and some step-by-step photos

(yes, it could have a better title, but I already had a ‘Bubbles I’ and this kind of stuck…)

I’ve been a long time getting round to showing you this picture properly. I finished it just before I broke my wrist in February, and at that point all playing with vinegar and copper leaf ceased – one day I’ll get back to more of this, I think it has some potential.

The main reason I never showed anyone was that it was difficult to photograph clearly so you can see what it really looks like, and I could never get round to organizing this series of pictures, but if you’ve bought anything from me recently you will have seen this painting on my ‘thank you’ postcards, and one or two people have asked about what it is, and whether I have prints – so yes, you can also buy prints in my Etsy shop here.

I love a chemistry demonstration…

If you hang copper over vinegar fumes you get a green corrosion product which forms on the copper – it’s called Verdigris. It’s been used as an artist’s pigment for centuries, though it’s fallen out of use as it’s not very stable and it’s a bit poisonous. Nothing on the scale of proper poisonous artists’ pigments – nothing like cinnabar, vermilion, orpiment, realgar and so on (lovely reds and yellows but oxides of mercury and arsenic respectively). You could still try this at home… but be sensible, don’t eat your resulting artwork!

The green patina on weathered bronze statues is often referred to as ‘verdigris’. It isn’t: unless it rains vinegar locally, it’s a mix of other oxides, sulphates and sulphites (it’s been a long time since that degree in metals conservation, so don’t ask me exactly what!), but it’s the same kind of chemical reaction. Verdigris is copper acetate – the product of copper and acetic acid (vinegar).

Gold leaf won’t react with (almost) anything, but imitation gold leaf is mostly copper. Brand new and freshly applied, gold leaf and imitation gold leaf look very similar indeed, but hang them (or put the picture face-down) over vinegar and something lovely happens. For the sake of accuracy – I am pretty sure not all the colours that you see in the corroded copper are verdigris – there’s a dark brown first, which looks like copper oxide, a bright blue at the end that looks very much like copper sulphate. The chemistry is probably quite messy and complicated… but the only added ingredient is vinegar, and a bit of warmth (the photo of the picture upside down was one I did last summer, in the greenhouse when it was warm – this painting actually perched on the warm Rayburn for two days and stank the kitchen out instead, but I don’t have a photo of that).

And the results – you can see for yourself. Experience has shown that you also have to use a spray-on varnish – the delicate surface is highly water-soluble and also reacts with the air to form different copper salts, and can loose some of its fabulous colours.  Varnishing seems to stabilize it, at least, a test run I did a couple of years ago seems to be pretty stable.

The figure of the swimmer was painted in watercolour, after the vinegar and before the varnish.
The finished painting is hard to photograph because the gold is still shiny and so it looks different from every angle. Putting the picture on a scanner picks up the details of the painting, but omits to show the glory of the shiny gold leaf, so I’ve shown both scan, and photograph from a couple of angles (above and penultimate image), which hopefully gives you a good idea of the painting, in changeable lighting.

And that’s it, I hope you enjoy my little album of step-by-step photos:

Pencil drawing on (stretched) watercolour paper

…protected (from the gold size) by masking fluid.

Gold size (fancy name for glue to stick on gold leaf).

Gold size again…

Still gold size – it’s all over the surface of the paper now.

Now for the imitation gold leaf…

Imitation gold leaf. Since the edges of the sheets will always show up, I wanted to place them so that they had some sympathy with the movement of the diver.

More imitation leaf.

Genuine gold leaf

The gaps and cracks between the imitation gold are now filled with real gold (you may be able to see a colour difference as I’m using a slightly different colour leaf too)

Off comes the masking fluid…

…peely…

Imitation and real gold stuck on, now for the vinegar.

Different picture, but the same process – vinegar goes in a plastic tray…. (you take it out of the bottle, yes….)…

And the picture goes face-down on top of it.

After a few hours.

And after a day or two….

Now you can see what is really gold.

Adding more flakes of gold leaf afterwards (stuck with a tiny drop of gum arabic this time)

Watercolour paint…

Finished the paintwork.

Texture – corrosion, watercolour and so on

more texture

…and more texture

Acrylic varnish.

Finished!

Scan of the painting – this is good for the details, but not great at capturing the glint of gold leaf or the glossiness of the brown areas of copper.