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Old 09-03-16, 09:38 AM
zarina zarina is offline
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Default Varnishing

Can anyone advise on a good high gloss varnish to use after finishing an ET painting. I know there is a school of thought which advises against using varnish, but as I paint large scale works, I am trying to do away with using glass to minimise weight. I love the resonance of ET when behind glass/varnished. I tried Gamsol the other day but it sank straight through without any effect. I was thinking of a water based/acrylic varnish as I think I've read they seem to yellow less (white is a dominant colour in my works so I'm not keen on any sort of yellowing of the paint surface over time). Any advice would be really helpful as I have not found much info on this anywhere, probably because it's not the thing to do with ET!
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Old 09-03-16, 06:23 PM
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Koo Schadler Koo Schadler is offline
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Hello Zarina,

It's common to read that egg tempera paintings should not be varnished - and it's true that the finish of a pure egg tempera surface is unique (not quite matte, not quite gloss; a subtle, one-of-a-kind, egg shell shine). But in fact, egg tempera paintings historically were varnished, and pretty much any old egg tempera you see in a museum has been varnished at some point in its life. There are pros and cons to varnishing, just as there are pros and cons to not varnishing. It's a personal (and hopefully informed) choice, up to the artist.

How to varnish properly is a challenge in most mediums, but more so in egg tempera (because traditional ET varnishes are outdated, there’s little contemporary practice of varnishing ETs, and relatively little research is done on ET in the conservation and art manufacturing worlds, since it is neither a very common nor commercially viable medium). Some of the issues include: traditional versus modern varnishes, how soon to apply, whether or not to first isolate the tempera (to avoid the sinking in problem you mention) - it's complicated. While I’ll try to comment on the specific questions you raise, there is a lot more that could be said. To that end, if you like I have a handout on the topic (too long to post) that I’m happy to forward if you send me your email address. I don’t mean to say the handout is a comprehensive look at varnishes – I’m still trying to understand the topic - but I have delved into it a bit because I too love the saturated, resonant look of a varnished ET.

As to your specific questions; Yes, any varnish intended for oil painting (such as Gamvar) can be used a top ET, but most of them (in my experience) sink into the surface and dry unevenly, with an inconsistent shine. I believe this is due to the high pigment to binder ratio that is characteristic of ET paint, as well as the great absorbency of a traditional gesso ground. If you first isolate the tempera (more on that below) before varnishing this mitigates sinking in, but I haven't yet figured out an ideal isolator (tho' I'm trying to!)

Spirit based coatings that dry via evaporation of their solvent (and hence dry quickly), such as shellac, tend to do a better job of saturating and covering an ET. Oil varnishes that dry via polymerization tend to sink in and dry more slowly and unevenly over tempera. The natural resins (damar, mastic, sandarac, etc) commonly used in the past are out of favor in the conservation world – too yellowing, brittle, and hard to remove with age (nonetheless natural resins remain popular with many painters, who may not mind the drawbacks - as mentioned, varnishing is a personal choice). Conservators prefer, as you mention, the modern, “non-yellowing” acrylic resins (of which Gamvar is one), but the ones for oil are solvent based and have that problem of sinking in as mentioned above (unless applied over an isolator).

My favorite isolator is shellac - quick, effective, and (after much experimentation) I tend to think non to minimally yellowing, but not everyone agrees on that last fact. It gets brittle with age, but the rigidity of tempera’s support addresses that, I believe. Shellac’s greatest drawback is that it is difficult to remove as it ages. I recently spoken with several material experts, each of whom recommended an isolator they think superior to shellac, including: water-based acrylic polymers (Golden GAC 500 medium and Soft Acrylic Gel Medium), a solvent-based PVA (Molwilith 20 PVA in ethanol), and a Casein-based spray fixative. The drawback of a water-based isolator (as well as a water-based varnish) is that the solvent (water) is also the solvent for tempera, which makes it a challenge to apply without disturbing the tempera underneath (you either have to carefully spray it on or wait many months for the tempera to fully cure). I am in the midst of experimenting with the above options and hope to understand them better, but I don’t yet. If anyone out there has tried them and can chime in, please do! In the meantime I continue to isolate with shellac but hope to figure out a better, “conservator-approved” isolator in the not-too-distant future (or find a conservator who is more approving of shellac!). Once I've isolated the tempera surface I then apply a varnish of some sort: one of the wax mediums, Golden's MSA, I've tried Gamvar too...I keep experimenting. So far wax is my favorite, but I'm still trying to figure out which final look I like best.

(By the way, wax mediums can be applied directly on top of egg tempera, no isolator is required, but only if the tempera has first cured for 2 to 3 months. If you don't have the time to let a painting cure for that long, as I don't, then the egg tempera must first be isolated - again, the ins and outs of varnishing are a bit complicated to fully explain here).

Okay, all of the above has perhaps left you more confused than helped. Varnishing egg tempera is too complex a subject to summarize in a single post (hence my more comprehensive handout). The problem isn’t so much how to do it: a layer of shellac, followed by Gamvar or Golden’s MSA or a wax medium works great. The problem is how to do it in a way that conservators fully approve of.

Let me add one more thought: for anyone who think these complications suggest that ETs should not be varnished, it’s important to note that properly varnishing an oil painting was once an unresolved topic too – but because there’s been a lot more attention and research devoted to varnishing oils, the topic is now better understood and resolved. I think there is a place for varnishing tempera paintings, notwithstanding the contemporary bias against doing so; the topic just needs to be better researched and understood. There are a couple of manufacturers looking at how to do so, and I’m diving into the process with them. I’m hopeful that a good, conservator approved practice for varnishing ETs will be figured out in the not-too-distant future.

Koo

Last edited by Koo Schadler; 09-03-16 at 09:46 PM. Reason: clarification
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Old 10-03-16, 10:04 PM
zarina zarina is offline
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That's a very comprehensive answer and it will be a great help in trying to experiment & see what works. I'll try the isolating shellac & one of the acrylic varnishes as you advise. Thank you for your very generous and detailed explanations - I do learn so much from your well researched articles and your extensive knowledge on the subject - a great help to those trying to work out how best to use ET, especially when pushing the boundaries a little in working methods!
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Old 11-03-16, 11:46 PM
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Koo Schadler Koo Schadler is offline
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It's fun to see people pushing egg tempera's boundaries, which I think are ripe for expansion. If you are new to shellac it's best to read up on it (via my handout or elsewhere); be sure to use an artist grade, bleached (platina) variety. And whatever finish you choose, it is most important, as I'm sure you know, to experiment on an inconsequential piece (or two or three) before applying it to important work. I haven't yet met a varnish that didn't take practice to learn to do well.

Koo
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Old 11-04-16, 02:02 PM
dbclemons dbclemons is offline
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I don't have experience with varnishing egg tempera, but do have with varnishing casein, which is very similar in structure. What I've done there is to apply an isolation coat to the casein after it has time to cure completely. That takes 3 to 4 months.

The purpose of an isolation barrier coating is to prevent the paint from being disturbed should the varnish ever have to be removed. Golden recommends that their best product for this is their Soft Gel product, unfortunately that needs to be diluted with water first. Instead, I apply 2 coats of Liquitex Acrylic Medium & Varnish, which can be used right out of the bottle. I apply the first coat very thinly with a brush over the shapes of the painting, making sure none of the paint layer gets disturbed. This is because some paint layers are thinner than others and not as strong. After 4 months of curing I've never had a problem yet, but it's good to be careful. The second coat can be applied with broad strokes from a larger brush and less concern. Once that dries the surface can be varnished with anything recommended for acrylic paint, such as MSA varnishes or Golden's Polymer varnish.
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Old 11-04-16, 02:14 PM
dbclemons dbclemons is offline
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Here's a link at Golden where they talk about varnishing watercolor that you might find helpful. The isolation layer they recommend is GAC 500 applied with a sprayer, or a can spray of their Archival Varnish. I've not tried these steps myself, and I'm generally wary of spray application (prone to drips and splatter.)

http://www.goldenpaints.com/technica...varnwatercolor

Last edited by dbclemons; 11-04-16 at 02:17 PM.
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Old 26-05-16, 12:44 PM
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Koo Schadler Koo Schadler is offline
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Default More on Isolators & Varnishes

Hello Everyone

Thanks for your input, DB – very helpful to hear from others on this topic.

How to do varnish ET properly (i.e. conservator approved) has long puzzled me, so I’ve been doing more in depth research and experiments. It’s illuminating but time-consuming, not fully satisfying - questions get answered but new ones get raised. Still, I’ve learned a lot, and now that I understand more I’m changing some of my past practices. There is a bit of a bias against varnishing ET, and consequently not ready information (it has seemed to me) on how to do it well. Hopefully, with the combined efforts of other ET painters who varnish, the picture is becoming clearer, so to speak.

Below is my synopsis of recent experiments with isolators and varnishes. Sorry for the length, I’ve edited but still it’s long - I didn’t want to leave out relevant info.

ISOLATORS
1. Is an Isolating Layer Necessary?
Input from various “experts” corroborates what I've felt: an isolating layer between egg tempera paint layers and a varnish is a good idea, for a couple of reasons. Most importantly, as DB says, an isolator protects the painting if its varnish needs to be removed at a latter date. Second it prevents sinking in, which allows a varnish to be applied much more evenly and successfully, and to dry more readily.

2. Criteria of an Isolator
Due to egg tempera’s absorbency, isolating layers penetrate into and possibly crosslink with the paint layers. In short, an isolator can be considered a likely permanent part of a painting. So it's important to use an isolator that (1) during application doesn't disturb the painting, (2) is minimally or non yellowing, and (3) is relatively flexible. Also, although it will probably link to a degree with the painting, it’s nonetheless best to use an isolator that (4) has a different solvent than the final varnish, and (5) is reversible.

(Many isolators and varnishes, with age, become yellow, brittle, and insoluble in their original solvent. They require stronger solvents to remove, which can lift or damage underlying paint. So “reversibility” - i.e. an isolator or varnish that remains soluble in it’s original solvent - is important).

3. Testing Isolators
I made three test panels coated with ET paint, finished with a single nourishing layer (yolk thinned with water). The panels cured for different lengths of time: one day, one week, and two weeks. These are relatively short cure times (one day, admittedly much too short!), but in my experience many painters don’t/can’t wait long before finishing a painting. When possible, it’s better to cure ET for a few months before isolating and/or varnishing, so those layers stay distinct from the painting.

4. Isolator Options
I tried 8 isolators, applied with either a sponge brush or soft-haired 1" flat brush

WATER-BASED ISOLATORS
1. Egg yolk medium (1 part egg yolk: 4 parts water)
1 coat. Minimal gloss.

2. Degas Casein Fixative
2 coats needed for coverage. Very watery & slower to dry. Covered well but slightly uneven. Minimal gloss.

3. Gamblin PVA
2 coats needed for coverage. Very watery & slower to dry. (Gamblin makes this PVA thin to cover canvas; a thicker PVA, such as from Talas, could be used.) Covered slightly uneven (due to thinness). Moderate gloss.

4. Golden GAC 500
2 coats needed for coverage. Thin but not watery. Set quickly, left some brushstrokes. High gloss.

5. Golden Soft Acrylic Gel Medium
1 coat covered. High gloss. Set with some brushstrokes.

SPIRIT-BASED ISOLATORS
6. Shellac, platina & de-waxed. (1 part shellac: 8 parts Denatured Alcohol).
1 coat. Moderate gloss.

7. PVA 20 Mowilith, from Kremer (1 part PVA: 4 parts Acetone)
1 coat. Moderate gloss.

SOLVENT-BASED ISOLATOR
8. Natural Pigments Conservar Isolating Varnish (thinned 10% w. mineral spirits)
2 coats. Slightly uneven, moderate gloss.

I expected the water-based isolators to dissolve and smear the egg tempera paint. None did, to my surprise (having a final nourishing layer on the ET no doubt helped). I like the spirit-based isolators the best because they dry very quickly, which means they sink in less and coat most evenly. However they dry so fast that for a large painting it could be hard to get a consistent application. The one solvent-based isolator from Natural Pigments worked well and is used in the conservation world; it has a strong, mineral spirits smell.

All isolators dried quickly (within 2 to 10 minutes), and all were minimal to non-yellowing. Shellac imparts the most yellow (albeit minimal, if thinned enough). It’s been my favorite isolator for years, but now that I know about synthetic options that are clear, more flexible, and reversible with age (unlike shellac), I’ll switch to one of them.

Isolator finishes ranged from satin to high gloss. This can be changed by the type of varnish applied on top, so isn’t necessary relevant.

The pure egg yolk isolator (essentially a second nourishing layer) was the least isolating. All others sealed well and greatly helped with the application of a varnish.

VARNISHES
Okay, onto varnishing. Here are some I'm experimenting with:

Conservar Finishing Varnish, Natural Pigments
Gamblin Gamvar, premixed
Acryloid B-72 (ordered from Talas, an online bookmaking supplier)
Golden MSA
Renaissance Wax
Conservar Wax Medium, Natural Pigments
Gamblin Cold Wax Medium

I applied them both directly atop egg tempera (no isolator), and on egg tempera with an isolator. The all behaved better (less sinking in, more consistent coverage), some significantly so, with an isolator under the varnish.

All have different characteristics – I’ll make just a few comments.

Both the Conservar Finishing Varnish from Natural Pigments and Gamblin Gamvar cover well, dry fairly quickly, have UV stabilizers, are non-yellowing & reversible, and uses a different (much less smelly) solvent (odorless mineral spirits) than the Conservar Isolator - so they meet all the criteria of a good varnish. The same synthetic resin (Regalrez) is used by the National Gallery to varnish. The gloss is fairly high but can be mitigated (as explained on Natural Pigments' website).

Acryloid B-72 is another synthetic resin, readily soluble in acetone. I got it in pellet form and it dissolved readily in acetone. B-72 is used by conservators to inpaint damaged areas on restorations and is one of the most stable of the synthetic varnish resins. It tried it as an isolator but it dried a little bit cloudy – I think it’s better as a varnish.

The wax mediums best approximate the organic, satin finish of a polished egg tempera painting. All worked much better atop an isolator (although I know ET artists who have luck applying wax mediums directly atop tempera, no isolator, as long as the tempera has cured for a few months). The Renaissance and Natural Pigment waxes have synthetic resins added, which makes for a harder varnish, slightly more shine. They are mineral spirit based (and thus a bit smelly). Gamblin’s wax is pure beeswax + odorless mineral spirit.

Strangely enough, Golden MSA had a distinctly yellow cast on top of egg tempera (more so directly on ET; still noticeable, tho’ slightly less yellow, over an isolator). I tried it on three different ET test panels with the same results (all from the same jar of varnish). I showed it to the technicians at Golden and they are very puzzled, said they will look into it. Golden MSA has a successful track record on acrylics and oils, but was not tested on ET, so a good example of why actual testing is useful (tho' it may be the fault of that particular can of varnish, not the varnish itself - or could it have something to do with egg? I'm not sure at this point, I'll report back if Golden figures it out).

(Aside –I spent a couple of days with the techs at Golden. Very knowledgeable, curious, not a commercial side of the company, not there to sell; they are there just to answer artists’ questions on any medium. As DB notes, the Golden website is informative and worth a visit; and the techs are a great resource for material related questions.)

A FEW FINAL WORDS...
Of course, it you love the look of unvarnished egg tempera, with its soft "egg shell" shine, you may think isolators and varnishes are unnecessarily problematic. There are pros and cons both to varnishing and not varnishing. It is a bit more work to isolate and varnish, and there is the downside of the isolator becoming part of the painting (hence a good isolator is important). On the other hand, a properly varnished egg tempera is better protected than an unvarnished ET; conservators commented on the fragility of paintings, how detrimental the environment can be, and how a good varnish can extend a painting’s lifespan. I also like the increased saturation, enhanced values and colors that an isolator and varnish impart. Understandably, it's not for everyone, but for those who opt to varnish, there are less and more durable ways of doing so.

Feedback, questions, your own experience with isolators and varnishes – all welcome.

Koo

Last edited by Koo Schadler; 26-05-16 at 02:57 PM.
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Old 29-05-16, 08:13 PM
dbclemons dbclemons is offline
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Very thorough testing, Koo. Thank you for that.

The results of Golden's MSA giving you a yellow tint is indeed curious. That's the varnish I use on top of the Liquitex Medium for my caseins, but never noticed any problem. Which isolator medium did you use it on? Perhaps you could try it again on a tempera painting that has had longer time to cure.
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Old 30-05-16, 06:28 PM
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Koo Schadler Koo Schadler is offline
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I used the Golden MSA Spray varnish on egg tempera with no isolator, and also on egg tempera isolated with Conservar Isolating Varnish - it yellowed in both instances. I also applied two other Golden MSA varnishes (gloss and matte versions) on two egg tempera panels (one isolated, one not); the egg tempera had cured for 2 months but both yellowed too. The gloss version yellowed the most, the matte the least, so that is perhaps a clue as to what is going amiss. I don't understand it at this point.

I also recently applied Renaissance wax over Conserver Finishing Varnish (to mitigate its shine), forgetting that both use mineral spirits (OMS, in the case of the Conserver Finishing Varnish) for a solvent. The Renaissance wax layers started to dissolve the Conserver Varnish - got a bit messy. So it's important to keep in mind that, to whatever degree you layer isolators and varnishes, consider their solvents.

Finally, I recently heard from a fellow painter who brought up the subject of petroleum based products. While irrelevant to some, it might be of interest to others that the various synthetic resins I'm talking about are all essentially different types of plastic, so to speak (synthesized polymers). Natural resins are biodegradable (if you can imagine your painting turning to dust someday...) and from renewable resources; the synthetic options obviously are not. Some painters would prefer a natural resin that yellows and gets brittle over a synthetic polymer; others would take the more durable material made from a non-renewable resource. You decide.

Then there is this upcoming dilemma - after all my kvetching about alternative gesso products that don't behave well with egg tempera (see earlier posts), a company is about to release a synthetic gesso that, of the many gesso alternatives I've tested, actually performs pretty well with egg tempera. It is less hygroscopic than traditional gesso (so not as susceptible to humidity), and vegetarian painters will be pleased (no more animal glue). On the other hand it is yet another synthetic resin and will be, in it's very modest way, adding more plastic to the world.

Happily I don't need to make these decisions for anyone but myself, but I thought it only fair to mention the above.

Koo

Last edited by Koo Schadler; 31-05-16 at 02:58 PM.
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Old 05-06-16, 08:36 PM
zarina zarina is offline
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Thank you for all your detailed responses - apologies for delay in replying. Plenty of research to look into and trial in the studio - it will be very useful to have this research at hand.

Zarina
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