The pros and cons of each:
As you’ll know from our studio manual, Glass Painting Techniques & Secrets from an English Stained Glass Studio (you can get a sample chapter here): once you’ve finished all the tracing, shading and highlighting you want to do with glass paint and water (and gum Arabic), then it’s often a good idea to carry on with glass paint mixed with oil (and no gum Arabic).
And then – you fire your glass just once.
OK, so the advantages of oil are … ?
Right. The advantages of oil?
- Easy shading
- Long-lasting batch of glass paint
- No paint loss in the kiln (it doesn’t get lighter)
- No dust.
The kinds of oil? Oil of Tar: oil of Lavender – whatever works. (And many oils do.)
The disadvantages of oil?
- A risk of over-painting
- The smell
- The toxicity e.g. oil of Tar is carcinogenic, Lavender is said to be unsuitable for pregnant women.
I write quickly here, since this is just to remind you of the topics we cover here.
But speaking of disadvantages, there is one in particular.
For some, this is worse than anything else the world might throw at us. It is worse than the evil smell of Tar oil. Even worse than the fact oil is poisonous.
Can you guess what it is?
You must be so clean!
Yes. All hell will break loose if oil contaminates any of the tools you use for the work you do with water. Just one drop, one careless drop of oil: that’s all it takes.
It is easy to have an accident which wrecks a costly batch of water-based paint.
Thus oil requires you to be scrupulously – no: surgically – clean.
And as I said, this is probably a lot for many glass painters.
Which is a crying shame, because, when cleanliness prevails and oil is administered with skill, the results are then as beautiful and subtle as any glass painting you will ever see.
And this takes me naturally to an especially helpful property of Propylene glycol …
Propylene glycol – you don’t have to be an angel of cleanliness
You see, it mixes like oil. It absorbs the dust like oil. Also like oil, you can make a batch which keep for ages and is very, very economical. Plus, it shades like oil.
All the same, it’s water-soluble.
So those saintly, other-wordly standards of cleanliness are simply not required of you. Which is good, eh?
Of course, it’s not the same as oil: not quite as subtle – you could tell the difference between an antique original done with oil of Tar and a modern copy done with glycol. But, other than for the fanatical demands of restoration, the choice is yours to make.
Yes, it is still advisable to keep a separate set of brushes and use a separate knife and palette. But you don’t have to take obsessive care. You can relax, get on with things; which is exactly how we like it.
Another advantage of glycol over oil is, you can trace with it and add new details.
Glycol – no bleeding
This is difficult with oil because oil tends to bleed. With glycol, there’s no bleeding. So after all the tracing and shading you do with water, you have a further opportunity to use glycol to add new detail. It is useful to have this opportunity.
If your nose is sensitive – mine is – it is also good that glycol is close to odourless.
In The Master & the Beast (the third documentary we made), you observe and study two demonstrations: one where oil of Tar is used, and one with glycol. In both cases, the basic procedure is the same:
- Apply a light, thin wash of oil / glycol mixed with just a little bit of paint
- Use a paper towel to absorb the excess
Your surface is now suitably prepared. So now you add your lovely shadows.
If you’re using glycol, you can also add new lines – safe in the knowledge they won’t bleed.
Watch this – oil of Tar
Here’s your first clip from The Master & the Beast:
Watch this – Propylene glycol
Here’s your second clip:
Do you see the difference?
With oil, you don’t usually add new lines (because they bleed); with glycol, you can.
The Master & the Beast
This documentary shows you two full-length demonstrations. Each one lasts 50 minutes. The first one – “The Master” – finishes with oil of Tar; the second one – “The Beast” – with propylene glycol.
If you haven’t seen this film, you can get it here.
All the best,
P.S. Two final points. First, you don’t use gum Arabic with oil or glycol. Second, you shouldn’t need to use a hair-dryer on the initial oil / glycol wash (before you start to trace or shade): this is because the water-based paint beneath will anyway absorb a lot; and the whole purpose of the dabbing and the blending is to absorb any excess.
P.P.S. Any questions or experiences you want to share? Please write a note. (Even though I’m in the south of France this month, I am still working.)