Oil Vs. Propylene Glycol

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 … ?


Glass painting with oil

Glass painting with oil

Right. The advantages of oil?

  1. Easy shading
  2. Long-lasting batch of glass paint
  3. No paint loss in the kiln (it doesn’t get lighter)
  4. No dust.

The kinds of oil? Oil of Tar: oil of Lavender – whatever works. (And many oils do.)

The disadvantages of oil?

  1. A risk of over-painting
  2. The smell
  3. 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:

  1. Apply a light, thin wash of oil / glycol mixed with just a little bit of paint
  2. Use a paper towel to absorb the excess
  3. Blend

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:

(Video not showing? First, hit your refresh button. Second, see answers here. Third, watch it here)

Watch this – Propylene glycol

Here’s your second clip:

(Video not showing? First, hit your refresh button. Second, see answers here. Third, watch it here)

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,

Stephen Byrne

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.)

21 thoughts on “Oil Vs. Propylene Glycol

  1. Propylene glycol being the primary compound in antifreeze, can antifreeze be used or do you recommend buying p.g. from a supplier.

    Thank you.

    • Hello Tim,

      Myself I would certainly suggest buying it from a supplier because you want to be sure it is as safe as it can be. PELI Glass Products will send you the right one (Lisa has a background in Chemistry and knows what she is doing).


  2. Yes, I have a question: where can I buy glycol? Is there a brand name or a company selling this product?


  3. Hi Stephen,

    I hope you are enjoying your holiday. A question: does one use the same badger for propylene glycol as for water-based paint?

    Also, when firing glass painted on both sides, the under side comes out matt. Can one turn this over and refire to make it gloss?


    • Hi Farook,

      Great time thanks! Working in the morning then time with my family in the afternoon.

      About the badger: for shading with glycol (and also with oil), you’ll find it far easier if you get a small round-headed badger (like you see in the clips). This is because it is far more responsive to your fingers than the big blended which you use for shading water-based glass paint.

      With oil, you must have a separate one. With glycol, you could in principle also use it with water-based glass paint (if you ever needed such a small brush) but all the same it is a good idea to keep separate brushes for separate media.

      As for re-firing; it may work – or you may find it now leaves the other side slightly flat. It is worth a test. (We haven’t done this ourselves because the need doesn’t arise for us.)

      Thanks for your questions. They help to clarify things for others which I otherwise omit to mention.

      All the best,

  4. Hi Stephen

    Aaah, sitting on the beach in France, perfect! Enjoy!

    Please could you sometimes post pictures of the finished articles in situ? It is intriguing to watch the panels being painted, and I for one, would love to see how they all fit together.

    All the best,

    • Certainly, Peta. The only reason we don’t usually post pictures of completed projects is, the Internet is so full of people saying “Here’s my latest creation …” and therefore we opted to focus on techniques. But now you mention it, I can see how, when we explain techniques, it would be helpful (and not boastful) to show you the finished windows. Thanks for the suggestion. Will do!

      P.S. “Beach”? Just explored the cathedral at Perpignan. Gorgeous stained glass: the sun is so much more powerful than in England, and it shows. (And also glows.)

      • Thanks Stephen, that would be amazing, and not at at all “boastful”. I have waited too long with baited breath to see an installation, that I had to bring it up!

        Well, you had a lovely picture of the beach on your post, but I am now even more jealous that you are in the refined constraints of a beautiful cathedral *sigh*

        • I’ve been thinking more about your idea while out and about in the magnificent church of Saint John the Baptist in Perpignan – some wonderfully gruesome murals there … And I can see more clearly now how detailed case studies will give the techniques we use a proper context. So thanks again for the suggestion. And hopefully “The Beastly Lion of Wolsey Towers” will be a step in this direction.

          • Great! I so look forward to it! Are you able to take and post some pics from St John’s? I think it would be fantastic to have a page on your site that we could all (followers of you) post some inspirational photos from churches and buildings in and around where we live, have worked on etc. We are all from such diverse areas on this planet, it would be fascinating to see what other people have in their countries.

    • Hi Patrice,

      Oil has its place. And, as you suggest, so does glycol – it is possible to do incredible things with it, as Deborah Coombs does for example.

      I hope all’s going well with the arrangements for the auction. I hope someone bids well for the painting course we’ve offered.


  5. Hi Stephen

    Propylene Glycol can be purchased from Amazon at about £7 or $4.50 per litre for pharmaceutical grade. Just go to the Amazon web site and type in Propylene Glycol. There are two types – Mono-Propylene Glycol and Di-Propylene Glycol – but I am not sure which type Williams & Byrne use in their studio? Could you let us know?

    There are possible health dangers with Propylene Glycol that should be mentioned. It is used as a penetration enhancer. It alters the structure of the skin and so allows chemical substances to penetrate quite deeply beneath the surface skin, even to the extent of reaching the blood vessels and entering the blood stream. Environmental health agencies rate it as moderately dangerous to health since it has been shown to be linked to cancer, reproductive problems, allergies, immune toxicology as well as disruption to the endocrine and neurological systems. Concentrations as low as 2% can be problematical.

    Surprisingly it is added to many common products eg shampoo, skin conditioners and moisturisers, soaps, toothpaste, deodorants, cosmetics such as mascara and nail polish. One may think it can’t be that bad, especially as millions of motorists use it as anti-freeze.

    Nevertheless it is worth being careful when using it in high concentrations, and try never to allow it to come into contact with the skin. If it does, immediately wash it off with copious amounts of water. It dissolves readily in water, making it relatively harmless.

    Best wishes,

    • Hello Selwyn,

      Thanks for your very useful contribution. We use Di-Propylene Glycol. It’s good to be aware of risks and their full context: ourselves, we’re fine to use it carefully, since it is so easy to clean off.


  6. I have a glass painting question which, I am sure, you guys know the answer to. I am running into the same problem over and over and it’s been driving me crazy!

    When painting with oil, the glass surface collects dust pretty much immediately, which shows up in painting as ugly messy little clumps. I hate it!

    So, I’ve tried water soluble mix made by Rosche for Rosche paints (which is Rosche’s version of glycol, I gues). It works great – paint does not dry quickly as it does with water, it is easily to manipulate, it is more dense than oil, not sticky and the mistakes can be fixed without disturbing the painting much. However, it attracts dust just like oil! I’ve been painting and re-painting the same 2×2 inch glass foot fragment the whole day today and I still can’t get rid of ugly dust clumps. Help! What do you do about the dust in your wet painting?

    Do you prep the brushes in a special way? Do you wash the walls and floor every day? Do you ignore the dust and just fire hoping it will dissapear? 🙂 I did, and no, it does not dissapear.

    Thank you!


    • Hi Rita,

      You’re not alone: we occasionally get dust. To solve the problem, you must isolate where the dust is coming from in your case.

      In our case, sometimes it comes from the kitchen paper with which we absorb the excess oil. When this has happened to us, we experimented with different brands of paper – the less lint / cotton fibre they give off, the better.

      The other main source is your brushes. First, you need a set of brushes which you keep just for oil. Second, you need to keep them scrupulously clean. We clean ours with a little oil of Lavender. In our case, dust rarely came from the applicator brush or from the tracing brush; it came mainly from the round-headed blender, so (we found) it was particularly important to keep the blender clean.

      It is also possible that somehow your batch of oil-based glass paint was contaminated right from the point at which you mixed it. If this has happened, you’ll need to start again, then take special care to clean your palette and knife as carefully as possible, then (from that point on) to keep your batch of oil-based paint well-covered when not in use.

      Will you please let me know how you get on?

      Thanks, Rita.


      • Stephen,

        I think you have it right on the money. The dust mainly appears after I use my oil blender. I tried washing the brushes with paint-removing soap and water and letting them dry before use, but the blender still introduces particles into the mat. It is totally possible that my basement studio is simply too dusty. I’ll start keeping my brushes locked in a lint-free box when I am not using them. Maybe that will help prevent dust from settling on them.

        I guess I should feel comfort from hearing that this is an ordinary problem…

        Thank you for taking your time to respond. I imagine you guys are incredibly busy and your attention is well respected and appreciated.

        Thank you and be well,


        • Hi Rita,

          Myself, I think if you (a) cover up your brushes when not in use as you suggest, (b) clean them thoroughly the next use, and (c) make a small new batch of oil-based paint, which you (d) be sure to protect from dust when not in use, then, fairly quickly, you’ll tame this problem. Sure, dust will happen, but it should really come down to the odd speck or two, not a swarm of spotty locusts.


          P.S. Sure we’re busy. But it’s good to talk. We enjoy the dialogue.

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