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MITRA Forum Question Details

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  • Metalpoint FixativeApproveRejectUn-ApproveSubscribeUn-Unsubscribe
    Question asked 2019-03-29 11:52:21 ... Most recent comment 2019-03-31 19:41:30
    Drawing Materials Varnishes

    I want to explore the idea of applying fixative or varnish to a metalpoint drawing.  My reasons are:

    1.  I combine metalpoint with fairly developed egg tempera painting on panel (see attached as an example: metalpoint lettering & egg tempera rabbit on Golden black gesso); the work, to me, appears too "removed" from the viewer when framed under glass - so I'm looking for a way to frame without glass that will nevertheless give some protection to the surface; i.e. a light spray coating of B-72, followed by a wax medium.

    2. In my metalpoint experiments (described in an earlier MITRA post) some metals and grounds, when exposed to a lot of sulfur, faded or completely vanished.  I understand the lesson: trying too rapidly to speed up tarnishing can be detrimental to a drawing. However, it also points to the potential vulnerability of metalpoint lines; the insecurity of their attachment to a support.  I realize there are many centuries-old metalpoint drawings in good shape, so I don't mean to say it's not a durable medium; only that it also has the potential to not hold up well. Additionally, I've heard two artists comment that drawings on "Plike" paper tend to "fade" or lose their metalmarks, but many metalpoint artists love working on Plike.  Would a fixative be a good idea for those people who opt for the convenience of a pre-made, less-than-ideal metalpoint paper?  

    I understand that a fixative (depending on how sealing or heavily applied) may slow or completely stop the tarnishing effect, but what if an artist doesn't mind or actually wants to deter tarnishing?   Would a light coating of fixative still allow for tarnishing?  

    In short, if fixatives are suitable for other forms of drawing, are they suitable for metalpoint as well?  

    Tho' I'm interested in subjective preferences, I primarily want to hear the objective, technical pros and cons.



Answers and Comments

  • EditDeleteModerator Answer

    Hi Koo

    You are probably have more experience with metalpoint than anyone else on this forum so I would defer to you on moist issues associated with the technique.

    I do not see an attachment but will try to comment.

    As far as fixatives, they are certainly a mixed blessing but are sometimes necessary. Too much will darken the paper or gesso ground due to surrounding the fibers/filler with a material of higher refractive index. Just the right amount will help keep the particles from being too friable. Obviously only non-yellowing fixatives should be used if possible.

    I do worry that if there is enough fixative to slow or stop oxidation/sulfation that the surface would really be quite saturated, changing the overall effect. Of course, this is an aesthetic decision and the result may be just what the artist is looking for (like your preference for lightly varnishing your egg temperas).

    I do not know what materials are used to finish Plike papers but they are obviously more than simply 100% alpha cellulose or they would not have the advertised feel of plastic and rubber and be resilient enough to take a metalpoint line without damage. Perhaps the surface it too compact to hold onto the abraded metal lines or one of the ingredients has a deleterious effect on the metal? This would require more testing to make a determination on this subject. I am very intrigued by your tests showing that the metal lines can actually “disappear” when they are overexposed to sulfur. I cannot imagine what the chemical process would be.  Was this liver of sulfur or another sulfur containing compound? If the problem is the paper having too slick a surface, a fixative my help, if it is chemical, it likely would not.

    Sorry that is not a very definitive answer but it is all that I can say given my limited knowledge here.

    Brian Baade
    2019-03-29 12:56:42
  • ApproveRejectUn-ApproveUser Comment

    Hi Brian,


    I just heard from a far more experienced metalpoint artist than I, Tom Mazullo.  He and Susan Schwalb just published a comprehensive book on metalpoint: 



    Tom says metalpoint on panel is sometimes varnished, and recommends Lascaux. 


    Plike is described as 100% sulphite paper.  I don't really know what that means. Seemingly it's produced from wood-free (lignin removed) primary pulp (cellulose) using ECF (Elementary Chlorine Free).  From what I read on line (I never finished chemistry, so excuse my ignorance here) sulphites contain one sulfur atom – so would that be enough to affect metalpoint in some way (accelerate tarnishing or degrade the marks)?  I agree, as you note, that the exceptionally smooth, compact surface of Plike makes it less able to grab onto metalpoint deposits; but then again, how does such a smooth surface abrade a metal nib in the first place?  That puzzles me a bit.


    In my tarnishing experiment, the fumes of apple cider vinegar did the most damage to metalmarks (completely erased most of them within 3 days); but Liver of Sulfur, and even a strong exposure to garlic and onion, "faded" or nearly erased some marks.  I don't understand what is happening– are the marks being broken down by the fumes, then taken up into the vapor somehow?  Is the paper being degraded too (and thus losing it's grip on the marks)?  Tom Mazullo says metal is reactive, dissolves in a caustic environment, so he thinks "the metal literally becomes part of the atmosphere, reacting with ions in the air, becoming a new compound and being carried away by airflow."  Sounds plausible but again I don't know. 


    I am always appreciative of your helpful replies. 


    2019-03-29 14:38:15
  • EditDeleteModerator Answer

    I had forgotten about Tom Mazullo and Susan Schwalb. I will be purchasing that book immediately.

    Plike papers may start out as 100% alpha cellulose but they must be adding other materials, sizes, etc, to make a paper that can be described as having the feel of a combination of plastic and rubber. Alpha cellulose should only be a polymerized polysaccharide.

    I am now wondering if it is not acidic conditions that are causing a chemical conversion of the metallic lines. Vinegar causing lines to disappear makes far more sense as metal acetates are often more transparent than alloys. Onion and garlic both contain sulfur groups that when in contact with moisture will convert to sulfuric acid. This is why your eyes hurt and tear when slicing onions. Perhaps a similar thing is occurring with the liver of sulfur.

    It would be very interesting to see if the same effect occurs in a desiccated environment. I once put a silverpoint drawing in a drying oven for a week or so and the lines definitely darkened some.  When I get some spare time, I will do the same but include some liver of sulfur. Perhaps this will accelerate the sulfation of the silver but because of the very low moisture no acidic conditions would be created.

    As to varnished metalpoint drawings on panel, the famous unfinished Saint Barbara by Van Eyck is essentially a varnished metalpoint drawing on a chalk glue ground with a bit of oil paint.

    Brian Baade
    2019-03-29 15:35:20
  • EditDeleteModerator Answer

    ​I've reached out to the Plike importer for more details on this paper and recommendations regarding fixatives. Will post if I get a reply.

    Matthew Kinsey, Utrecht Art Supplies
    2019-03-29 16:31:34
  • EditDeleteModerator Answer

    ​Thanks Matthew. I was planning on doing the same but your assistance is of great help.

    Brian Baade
    2019-03-29 16:55:04
  • ApproveRejectUn-ApproveUser Comment

    ​Thanks for the replies.  Brian, that's interesting about the acid, I will keep it in mind.  Tom & Susan's book talks a bit about Plike under the section that discusses clay coated papers; it says such papers are "imprinted on both sides with a polymer that contains compounds like kaolinite".  So that seems to be the material used to finish plike.  If you hear anything from the company, Matthew, I'd be most interested.


    2019-03-31 18:48:41
  • EditDeleteModerator Answer

    ​The Plike importer has reached out to the manufacturer for more information, but is not sure they will be willing to disclose any details of the coating formula. He said, quite directly, that Plike is not clay coated, and mentioned twice (with emphasis the second time) that Plike is made for commercial and packaging applications, and is (as we already know) not made expressly for metalpoint. (The trademark name "Plike" is apparently derived from "plastic-like".) He offered to recommend some other papers, and I said, for now, I would like to focus on Plike, for the benefit of artists using it, and conservation specialists who might have to treat works on this stock. I said that there would be interest in even the broad category of polymer used, and any recommendations for fixatives/top coatings. He did say to stay tuned, so there may be more to come. 

    Matthew Kinsey, Utrecht Art Supplies
    2019-03-31 19:41:30

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