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  • Gamvar for egg tempera or alternativesApproveRejectUn-ApproveSubscribeUn-Unsubscribe
    Question asked 2019-10-22 11:46:42 ... Most recent comment 2019-10-31 04:26:45
    Varnishes Egg Tempera
    Question

    ​I have a question about varnishes for egg tempera.  Until recently, I used boiled linseed oil, but it is a tremendously problematic varnish which changes the nature of painting (lead white becomes transparent, azurite becomes green etc.)  So I decided to seek something better.  Several substances came to my attention, one of them was GAMVAR.  I tested it and got very unpleasant surprise: wherever Gamvar came into contact with egg tempera paint, dreadful white spots appeared.  NOTE: those were not "blooming", I'd know the difference.  This was some kind of whitish residue that appeared on top of the painted layer, while Gamvar completely sunk into the paint.  Under-tempering is not a factor in this, I temper my paint quite well (egg-shell sheen), and apply nourishing layers often.  I also know that those whitish spots look exactly like when I had to clean gilded parts with mineral spirits, some of it got onto the paint and bleached it immediately.  

    My friends who work in oil swear by Gamvar.  I decided to persist and varnish the painting I just finished with Gamvar, and even after 6 consecutive coats, there are lots of sinking as if it goes through the paint like through a sieve.  

    Anybody had experience with this or has other varnishing options for egg tempera?  The properties I seek are:

    1. Non yellowing
    2. Something which would not cause blooming
    3. Reasonably strong to protect the painting


Answers and Comments
  • ApproveRejectUn-ApproveUser Comment

    ​I think gamvar has gamsol in it which is an odourless mineral spirit. Could you try to paint over the egg tempera with a clear acrylic isolation coat (as Golden advise for acrylic paintings), and then apply a varnish layer?

    2019-10-23 09:06:39
  • ApproveRejectUn-ApproveUser Comment

    I'm a tempera painter, not a conservator –I'll be interested to hear what the conservators have to say.  For now, here are a few thoughts based on many years experience varnishing egg temperas.

    Because egg tempera is such a high PVC (pigment volume concentrate) paint, its surface is very porous and absorbent.  Same goes for a traditional gesso ground.  So both are like sponges, and anything you apply sinks in (or, as you aptly say, goes through like a sieve).  

    To successfully varnish a tempera, you must first isolate the tempera with a thin layer of a fast-drying coating. You want the layer thin because you want to minimize excessive, unnecessary coatings on a painting; you want it fast-drying so it doesn't have the "chance" to sink in.  Conservators generally recommend Paraloid B72 as an isolator.  It's flexible, non-yellowing, and remains removable by its original solvent as it ages (although removing anything form an irregular, porous, high PVC surface is a challenge. You can basically presume an isolator becomes an integral part of a tempera painting - unless you're Andrew Wyeth or the equivalent - as it would take a lot of time for an experienced conservator to remove).  You can buy B72 in pellet form (I got some from Talas) to dissolve yourself (acetone, ethanol, toluene, xylene) and apply with a sponge brush; or there are some commercial products in spray cans made from B72 (including, last time I checked, Lascaux Spray Varnishes and Krylon Crystal Clear Coating).  Both applications have their challenges; a sponge brush can leave ridges as the isolator quickly dries, spray application can create orange peel – so it's critically important to practice on inconsequential works and get good at applying an isolating layer before doing so on important artwork.

     I've tried other isolators on tempera, including: super blonde shellac, water and solvent based PVAs, Golden GAC 500 & Soft Acrylic Medium (as the other poster suggested), Casein Fixative and Laropal A81.  All worked, all have pros and cons, none is necessarily better than B72 (depends on your goals and preferences) - just want to clarify that there are many options. 

    Once the tempera is isolated, you can apply pretty much any varnish you want on top.  

    As to the question of bloom, there is more than one kind of efflorescence (mold, salts precipitating out of a pigment, fatty acids as discussed below); essentially anything that comes up and "flowers" onto the surface.  People sometimes talk of a moisture-based bloom in tempera, but I don't think this is correct – there's no place for moisture to get "trapped" in a tempera painting because its porous surface allows for moisture to evaporate out.  

    In my experience, under tempering (too little egg yolk in the paint), isn't as common as over tempering (too much egg yolk).  There is a correct ratio of yolk to pigment in egg tempera paint, and more yolk is not beneficial.  On the contrary, excessive yolk can lead to Fatty Acid Migration, a type of efflorescence that can occur in tempera (and occasionally oil) paintings.  If the paint film has too much binder in it, extra lipids migrate to the surface and create a whitish fuzz; it can happen within months to many years after the completion of a painting.  I see examples of FAM fairly consistently, often from painters who apply nourishing layers.  If you are tempering well, nourishing layers are not necessary and potentially problematic – I recommend against them.   

    In fact, I'm wondering if the bloom you are seeing might be FAM –perhaps, as the Gamvar sinks into the surface it's helping to "push" out excess lipids?  FAM is believed to be exacerbated by high humidity but not suppressed by low humidity.  It is seemingly less common in small panels, more prevalent in large panels (See Dr. Joyce Stoner, Erasing the Boundary between the Artist and the Conservator, AIC Paintings Specialty Group Postprints, 2000).  Although not a well-understood phenomenon of egg tempera, there is some suspicion that isolators and varnishes suppress FAM in tempera – which would argue against your bloom being FAM.  So I don't know what the bloom is.  This is the point at which we need a conservator to chime in.  

     

    Koo Schadler

    2019-10-23 12:24:55
  • EditDeleteModerator Answer

    I actually have little to add to Koo’s response. I have not varnished many egg tempera paintings that had not already been varnished in the past.

    I do have a question about the Gamvar. Was it satin or matte? The only time that I have encountered a similar effect was when I applied a varnish containing a matting agent to a very absorbent surface. The varnish was drawn into the paint leaving some of the matting agent at the surface. This was very disfiguring.

    I will sent this thread to representatives from Gamblin and a conservator who has more experience with varnish on contemporary egg tempera paintings.

    Brian Baade
    2019-10-23 12:37:56
  • ApproveRejectUn-ApproveUser Comment

    To Koo's point, I would expect Gamvar to quickly sink into absorbent egg tempera layers. The other varnishes she mentioned have a higher molecular weight compared to Regal Rez 1094 (the resin in Gamvar), and in turn, will likely result in a more concentrated coating on a porous surface.

    Also, per Brian's question – Gamvar Satin or Matte (or any varnish containing matting agents) will result in whitish reside due to the solvent/resin components sinking into absorbent paint layers and leaving the larger matting solids on the surface.

    Both Regal Rez 1094 and Laropal A-81 can be purchased in dry form through our Conservation Colors site.  

    Kind regards,

    Scott Gellatly

    Gamblin Artist Colors

    2019-10-23 13:47:24
  • ApproveRejectUn-ApproveUser Comment

    ​Thank you, Koo, Briand, and Scott!
    The gamvar was glossy (not satin or matte), so no chance to leaving the matting agent on the surface.  I suspect it has something to do with what Koo mentioned, that Gamvar pushed up something to the surface, some grayish-whitish film which I was able to rub off with a piece of cloth.  Since it was my first experience with Gamvar, I proceeded to apply several coats of it.  After a week and 7 coats, I had to remove it all as it looked ghastly.  It didn't even look like egg tempera but like something plasticky.  

    As I removed Gamvar with Gamsol, it also removed some of the paint film; upon drying, mineral spirits in Gamsol "bleached" the painting.  Not sure I can rescue it...

    George O'Hanlon sent me two varnishes from his line, Laropal Isolating varnish and Regalrez Finishing Varnish.  I tested them on some spots, they both sink into the paint film, and as long as they render the tempera water-insoluble, I am fine with it.  But they are not super-strong and do not protect the paint film from abrasions. (I used them on water gilded surfaces and they didn't hold well)

    What would you think if I did the following:
    Isolating coat with Laropal, and then the finishing coat with Lascaux Gloss Acrylic varnish (waterbased)?  (I have seen people using Lascaux Gloss varnish, it does not look glossy at all, more like egg-shell.)  

    2019-10-23 15:46:21
  • EditDeleteModerator Answer

    I would worry about the adherence of an acrylic dispersion over a solvent-based isolating varnish. Yes, it is very easy to overdo Regalrez-based varnishes and create a nail polish-like effect. As Koo indicated, it is usually best to isolate the paint with a high molecular weight varnish like B-72 that will not sink too much into the stratigraphy and apply a thin application of a lower molecular weight varnish like Regalrez or Laropal A-81 to the top.

    As to the Natural Pgments products, I am guessing that George has his varnishes formulated in solvents that allow for the application of the Regalrez over the Laropal A-81 without biting into the isolating layer.

    Brian Baade
    2019-10-23 15:58:23
  • EditDeleteModerator Answer

    It would probably be best to avoid acrylic dispersion coatings directly over egg tempera. The alkaline pH levels in water-based acrylic coatings could potentially have damaging effects on the fatty acid fractions in the egg tempera and the proteins. Although, we have heard repeatedly of artists who have accidentally applied Golden Polymer Varnish (water based with pH level leaning towards the higher end) over their oil paintings, and they looked fine.

    We have never seen adhesion failure of acrylic dispersion coatings over mineral spirit based acrylic (MSA Varnish), at least. But because it complicates the layering for possible future conservation treatments, Golden generally does not recommend dispersions over solutions. Better to apply easily removable coatings over less soluble ones.  

    To err on the safe side a solvent borne acrylic varnish, like Paraloid B72 or MSA/Archival (spray) Varnish would probably be the best isolation varnish, followed by lower molecular weight one, like Laropal or Regalrez. Being able to remove the Regalrez without the acrylic varnish underneath would be a great advantage and if Regalrez does not sink it really creates beautiful finishes. You might also be happy to leave it with the first varnish. You can find tips on manipulating sheens of solvent based varnishes here: Tips and Tricks for Varnishing

    Mirjam Hintz
    2019-10-24 03:50:35
  • ApproveRejectUn-ApproveUser Comment

    Another option (the one I prefer) is to isolate the tempera, then apply a wax medium on top.  Wax mediums are not as protective as, for example, Regalrez - but there is (along with the isolator) some protection, and the finish isn't too glossy or plasticky, more soft and organic-looking, akin to the natural finish of egg tempera. 

    You're description of the grey-ish whitish substance that you were able to wipe off sounds like FAM (which, by the way, is the treatment for this efflorescence - you simply, gently wipe if off with a soft rag), but I haven't heard of those circumstances (i.e. that a varnish instigated it). Do the conservators have any thoughts on the possibility of the Gamvar soaking in and pushing out excess lipids?  Is it feasible?  If not FAM, any other thoughts on what the efforescence might be?

    As for your colors appearing "bleached out" after cleaning off the Gamvar, not sure what explains that. Is it possible that, as the varnish was dissolved by the application of solvent, and then whatever varnish remained in the porous paint layers re-hardened, it "trapped" some of the exiting fats to create essentially a semi-transparent, white scumble around pigments that lightened them?  Speculation, of course....just trying to understand why the colors now appear bleached.

    Be cautious of applying too much strong solvent atop egg tempera.  My understanding is that they can swell and thus potentially stress and weaken the paint film, and draw out plasticizing components, which can lead to embrittlement.  

    Koo

    2019-10-24 07:01:45
  • EditDeleteModerator Answer

    Mirjam

    I should have been more clear. You are right that there is no incompatibility of putting an acrylic dispersion over an dried solvent-born acrylic coating. I do worry about it over the aldehyde resin.

    Brian Baade
    2019-10-25 19:47:49
  • ApproveRejectUn-ApproveUser Comment

    ​Here is a bit of observation regarding this "bleaching out" after applying Gamvar and even more so after removing it with Gamsol (which is mineral spirits essentially).  I coated the bleached out areas with a somewhat diluted egg emulsion, and the bleaching disappeared.  It is hard to tell what it is.  It could be an optical effect, but it can also be some deposit brought to the surface by mineral spirits.  

    More to it, when gamsol made the painted layer to peel off - not everywhere, but where the coat was rather thin.

    2019-10-28 09:53:42
  • EditDeleteModerator Answer

    ​There doesn't seem to much literature on egg tempera and solvent interaction. The most recent study I found is almost 10 years old. P. Cremonesi et al. (https://repository.si.edu/bitstream/handle/10088/20487/09.Casoli.SCMC3.Mecklenburg.Web.pdf) have tested various egg tempera samples: non-polar solvents (iso octane) extracted significantly more material (mainly fatty acids and cholesterol), than polar solvents (water, ethanol, acetone). Water only extracted amino acids from the proteinaceous fraction. Pigmented layers were less prone to FFA leaching than pure medium layers. Most samples remained visually the same after solvet contact.

    Seeing that non-polar solvents have such FFA leaching potential it might be saver to varnish tempera paintings with materials which are diluted and remain soluble in polar solvents, e.g. Laropal in alcohol. 

    Mirjam Hintz
    2019-10-31 04:26:45
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