Why Your Paint and Medium Sometimes Doesn’t Stick: The Beading on Your Canvas and How to Fix It

Yes, I promise, I’m really going to give you the solution.

So, for all of this fuss about paint or medium acting like “beads on a duck’s back,” it turns out the duck knew why all along.  So did Max Doerner.  Which is a good thing, because if it had been left to my powers of deduction it would have remained a mystery unsolved.

Why does water run off a Duck’s back?  Rumor has it (i.e., Yahoo! Answers) that ducks have something called a “preen gland” that produces a waterproof mixture of waxes and oils.

So guess why your paint or medium (when you “oil in”)–or even varnish–sometimes forms beads on an already-painted surface?  Yep, oil.

The solution?  I’ll pass this on to Max…

If, because of its oiliness, the ground takes colors poorly, it may be rubbed off with a slice of onion or potato, or better still, with dilute ammonia, also with alcohol.

A few sentences later he says something similar, but even more precise:

One must, before using, rub off such canvases as feel oily with ammonia or alcohol in order to improve the adhesion.  Rubbing with a potato or onion only prevents the trickling of the colors and does not improve the adhesion.

So something I hadn’t known the answer to for a long time (though I had suspected and experimented with a potato… with modest results) has apparently been known for a long time, or at least since 1934 when Max Doerner published his book “The Materials of the Artist and Their Use in Painting.”

I should add that I have since tried resolving this problem with alcohol and it works like a charm.  Just don’t use too much as it will pull just a little color off the surface.

And I must hand it to Max; he knows his paint… and his painting.  The last sentence of the author’s preface reads:

It (the book) is not intended as a course of instruction in painting, because it is no more possible to learn to paint from books than to learn to swim on a sofa.

20 replies
  1. tja
    tja says:

    After more than a year since this post, my experiments and investigations on this matter have continued. Here’s an update:

    If you try and bring the saturation back to your color by rubbing on some of your vehicle (“oiling out”) and it beads, then the best overall fix is to use some retouch varnish. I use either Zecchi’s (from the famous art shop in Florence) or, one that is probably easier to find at a local art shop, Lefranc & Bourgeois Extra-Fine Retouching Varnish.

    Why this instead of wiping the surface with alcohol? Well, two reasons:

    1. By painting on a thin layer of retouch varnish rather than rubbing off with alcohol, you run less risk of removing paint, and;

    2. The resin in the retouch varnish assists the adhesion of subsequent layers.

  2. Kathleen Staiger
    Kathleen Staiger says:

    I have some questions: (1) I paint fairly large canvases (30×40 is my smallest) and brushing on the RV is cumbersome; could I use a spray retouch varnish? (2) Can I assume the RV would be applied to the entire canvas before beginning to oil out (I have never had any canvas that did NOT bead up somewhere)? (3) Should I oil out into the wet RV or wait for it to dry? I have been coping with this problem for many years and greatly appreciate your input into the problem!

  3. tja
    tja says:

    Hi Kathleen,

    Here’s what I learned about a month ago from a restorer who works at Kremer. She said:

    If your paint is beading on a pre-painted surface, then you need to either:

    a) Take some solvent (turpentine, Sansador, etc.) and wipe away the surface to remove the excess oil, or;

    b) Take some sandpaper and gently sand the surface.

    It has been a while since I have encountered this problem, but I would not that I have also changed my medium to half Linseed oil, half Shel Sol (an odorless solvent).

    Obviously, this makes my medium leaner… and probably helps me avoid an excessive build-up of oil on my surface.

    I hope that helps.

  4. Kathleen Staiger
    Kathleen Staiger says:

    Thanks for your reply, but it doesn’t really answer my questions. Regarding your entry on the use of retouch varnish to combat beading up, I wondered whether it would work with spray varnish as well as brushed on varnish, and whether it could be painted into while still wet or should dry first. These are the two questions that I would really like an answer to if you have one. My routine medium is the same as the one you now use and I run into problems when I apply either a glaze or oiling out (for which I use my medium) not when I am painting normally. I have tried the method you describe in your reply (except for the sanding) before with limited success. That is why I was interested in your discussion of the use of alcohol when I came across it. This worked a little better, but still not perfectly.

  5. tja
    tja says:


    I think what I was trying to point out is that using the retouch varnish doesn’t really address the problem as I now understand it. For example, here is another way to address the actual problem (the paint not adhering to the surface), as explained by Marc Dalessio: http://www.youtube.com/watch?v=JmM_SsFLSGA

    But to answer your question(s): I do sometimes apply retouch varnish then paint into it while it is wet, though now I’m using the retouch varnish mainly to bring back the color (i.e., as a way to “oil out,”) and not to deal with a beading surface.

    I do not use spray varnish, but the one by Lefranc mentioned above, so I can’t advise you there. I would certainly contact the manufacturer and ask them the very same questions you’ve asked me; that is the best way to get an informed response… assuming they are kind enough to do so.

    And if they do, please let me know what they tell you. I’m always keen to hear from the “experts.”

  6. Anthony Apesos
    Anthony Apesos says:

    Beading can be stopped by painting linseed oil to the area in question and buffing it with a soft lint-free rag, and then wiping it all off. this breaks the surface tension and a glaze will go on very nicely.–obviously the paint you are buffing must be dry.
    This will also bring up the color if it is dulled.

    retouch varnish is not a good idea at all–varnish should not be in the painting–only on it

  7. tja
    tja says:

    Anthony, many thanks you for the input on this. The next time I encounter the beading problem I’ll try your recommendation.

  8. Anthony Apesos
    Anthony Apesos says:

    before i used this method i avoided beading by rubbing the surface with a raw potato!–it worked but there did seem to be a starchy residue. the potato trick is something that i read that G. F. Watts did.

  9. tja
    tja says:

    Anthony, yes, as I wrote above in the original post, Max Doerner suggested:

    “If, because of its oiliness, the ground takes colors poorly, it may be rubbed off with a slice of onion or potato, or better still, with dilute ammonia, also with alcohol.”

    So, re-thinking the chemistry, I am somewhat puzzled by your suggestion to add more oil. ?

  10. Anthony Apesos
    Anthony Apesos says:

    it is not the oiliness itself but the smoothness of the surface that the oil creates in the dry surface that causes the beading. rubbing the oil into the dry paint somehow breaks the surface tension of the smooth surface that causes the beading. the essential thing is that i am not just adding more oil–i am rubbing it in and then wiping most of it off. anyway, the fact is, it works.

  11. tja
    tja says:

    Anthony, I believe you. I’m curious to know the scientific explanation of how that “somehow” works, be it oil, a potato or an onion. Should you come across one, I’d be happy if you could pass it along.

  12. Anthony Apesos
    Anthony Apesos says:

    good question. the smooth surface repels the liquid glaze and these techniques alter that surface so that it does not repeal the glaze. the answer must be on the molecular level but what the answer is i don’t know.–but almost everything i do–do i dare say “we”?–is a “somehow” that we do with only a vague “scientific” understanding.

    another related question–why does the water based paint made with egg white-(glair-) not bead up over dry oily paint? that i believe is what Caneletto used for much of his fine line work in his architecture :


  13. tja
    tja says:

    Anthony, there is no question that for a long time my scientific understanding of oil painting was “vague”. Since 2010 I have been pretty passionate about reducing my level of ignorance, hence my interest in understanding better.

    I’d say the reason the emulsion doesn’t bead is because of the egg. I did do that once–an emulsion over oil (for the riggings of a ship, no less)–and it worked like a charm.

  14. Anthony Apesos
    Anthony Apesos says:

    yes it is the egg–but as you asked of me–what is the scientific reason?

    i am not suggesting curiosity about what causes paint and vehicles to do what they do chemically or optically is not worth knowing when i ask the following question–it is certainly interesting to me–but will it make one a better painter?

  15. tja
    tja says:

    Anthony, does scientific understanding of our materials make us better painters? I have no doubt that it benefits the integrity of the construction and subsequent longevity. Does it impact the quality of the aesthetics? Trickier question. Wouldn’t that be a kick if it did?

  16. Anthony Apesos
    Anthony Apesos says:

    would it?–i am not sure how–
    i think knowing what works and not how it works is all one needs–it was enough for the old masters–though it is fun to know stuff

  17. tja
    tja says:

    Anthony, I found something curious today; a post from 2011 in the wetcanvas forum led me to a website that a combines the onion and the oil:

    “8. Before each new layer the canvas (ideally dried during 7 weeks) is carefully wiped with a half of an onion (in order to prepare the dried surface to absorb better) and then with linseed oil. After that the canvas is wiped with a soft piece of cloth.”

    Here’s the link:

  18. tja
    tja says:

    Since the original post six years ago, here is what I presently understand:
    If the paint beads, that means that the paint/medium is not ‘fatter’ than the surface, meaning, it has less oil in it than the surface does. So, to fix the problem, do two things:
    1. Sand the surface with some fine sandpaper and/or;
    2. Use a medium that is ‘fatter’ than the surface, meaning a medium that has more oil than what is below it.

    I would also note that since I now am more careful in painting ‘fat over lean’, meaning, starting the painting with only Shelsol-T (citrus solvent) and then gradually adding more oil to my medium, it has been some time since I have encountered this problem.

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