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Old 07-04-18, 01:51 PM
PatrickKing PatrickKing is offline
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Default Painting over old egg tempera paintings

Hello,

I'm just getting back to egg tempera after not touching it since art school.

I have a number of unfinished paintings that have been sitting around for about 30 years. If this were any other medium I'd simply jump back in and rework or paint over them. I'm not sure however, if that's safe to do with egg tempera. I've searched all over and can't find an answer, so I was happy to discover this forum.

Thanks in advance.
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Old 15-04-18, 02:52 PM
Koo Schadler's Avatar
Koo Schadler Koo Schadler is offline
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Hi Patrick,

Paintings are complicated structures: Multi-layered, disparate materials asked to co-exist happily with one another, generally for the long term. I don’t think it’s requisite to care about durability, I just think painters should know enough to willingly choose it or not. Some painters neglect durability because they are painting for their own pleasure, and that’s fine (although don’t underestimate how cherished a painting might become to future generations). And I understand that even a well-made painting kept in harsh conditions can fall apart. With those caveats, here are some considerations regarding working on an aged painting.

1. How dirty is the surface?
2. How well does fresh paint behave atop the surface?
3. How well will fresh paint adhere?

Step 1. Clean the Surface.
Aged paint surfaces accumulate dust, grease, nicotine, mold, dead insects, splattered spaghetti sauce - you name it. For the paint to behave and adhere you must have a clean surface.

Even a very gentle cleaning can abrade egg tempera. ET has very high PVC (Pigment Volume Concentrate), which means the quantity of pigment is so great relative to the yolk binder that pigment particles slightly protrude above the paint surface; the surface is not fully “sealed” (unlike oil painting, which have a smooth, sealed surface because the oil binder fully covers pigments). High PVC paint creates a microscopically irregular surface that not only traps dirt and dust more readily, but also is harder to clean without abrading the slightly protruding pigment particles.

In an ideal world you’d call a conservator because cleaning a painting (especially egg temperas) without harming underlying layers is tricky. Conservator aren’t always as expensive as one may think – AIC (American Institute for Conservation) is a good US resource for finding one:

http://www.conservation-us.org

I realize this probably isn’t relevant to your question. But I have to mention it because I’m in trouble as soon as I suggest that an artist clean the surface of a painting himself; it's risky without proper training. Just so you realize that.

To Clean: Once egg tempera has fully cured (takes 3 to 6 months, so at 30 years you’re good) it is somewhat durable and no longer water-soluble. First gently brush off all dust. For paintings that aren’t very old and/or have been protected, this may be enough to clean the surface. However if a work has been sitting around for years (or decades) and/or was left exposed, you’ll probably need to next clean with mild soap and water. Don’t use detergents, just a very gentle and absolutely minimal amount of soap. Better yet, Natural Pigments makes a Picture Clean Gel (and also offers a good article on how to clean paintings; see https://www.naturalpigments.com/art-...oil-paintings/). Use a very soft, only slightly damp cloth and don’t oversaturate the surface. Test a small corner of the painting to make sure paint isn’t lifting before you dive into the whole thing.

Instead of soap and water you could wipe the surface carefully with denatured alcohol – it works well at removing dirt, grease, etc. The problem is alcohol draws out plasticizing elements in the paint film, which increases brittleness. So alcohol is faster than soap and water, less abrasive to the surface of the painting initially, but more harmful ultimately. Alcohol is effective if you don't care about durability.

Step 2. Get the paint to behave.
How well the paint behaves depends, to a large extent, on the surface. A tempera painter who works exclusively with fine hatch strokes in just one or two layers is asking much less from a surface than a painter who does a hundred layers via brushwork, sponging, splattering, thin glazes, etc. I'm not trying to unnecessarily complicate the issue; it’s just that the longer I teach tempera, the more I appreciate that people have very different methods and this is relevant to what they need from a paint surface (as well as from their paint, brushes, everything else). One size does not fit all.

The working properties of egg tempera are, to a large extent, influenced by how much water is in the paint and the absorbency of the surface to which it’s applied. The most likely problem working on an aged film is that the paint beads up, doesn’t flow. This is because the surface of a fully cured painting is less absorbent than raw traditional gesso or a fresh layer of tempera paint. Dry brush can be managed and controlled pretty well even atop a less-than-ideally-absorbent surface. Watery paint is best controlled on an absorbent surface. So if you try to paint on your old paintings (after they’ve been cleaned) and the paint beads up, or if you work with watery paint at any point in your process, I recommend (after you clean the surface) that you next very lightly sand the surface. The goal isn’t to abrade/remove paint, it’s to open up the paint and create a bit of microscopic texture for fresh paint to grab onto. I use 1500-2000 grit micro sanding sponges (available from auto body stores or good woodworking suppliers).

If, after sanding, the paint still doesn’t behave, try coating the entire painting with a very thin “nourishing layer”; i.e. egg yolk medium thinned with water, about 1 part yolk to 8 or 12 parts water (depends on how fatty the egg is). You don’t want to lay down a gummy mess but merely a very thin layer of yolk to help paint grab on and behave. Don’t overdue nourishing layers – too much excess yolk in a paint film contributes to brittleness, cracking, and something called Fatty Acid Migration (excess lipids or egg oils migrate to the surface and leave a fuzzy residue. FAM is usually readily brushed off from the surface, but still not desirable).

Step 3. Does fresh paint adhere?
We are back to the topic of durability. Egg tempera, if you can get it to behave, will stick to many surfaces in the short term. This sometimes leads people to say you can apply ET to anything, which you may; but for egg tempera to adhere long term it needs absorbency to create mechanical adhesion (the paint and surface interlock; think sewing or Velcro).

How soon does poor adhesion create a delaminating paint film? It’s impossible to say because it’s dependent on too many factors. Poorly adhered paint may stay put for decades if kept under pristine conditions (i.e. in a museum). So you could skip step 1 & 2 above, potentially create a poorly adhered painting, and not see any consequences for a long time. Then again, I’ve seen delamination begin in as little as one month after completion of an ET painting. Suffice to say that if you want adherence, attend carefully to the first two steps. If you clean the surface well, open up the surface, and create good adhesion you should be able to work on 30 year old egg temperas and get good results.

Hope that helps,

Koo

Last edited by Koo Schadler; 15-04-18 at 03:07 PM. Reason: clarity
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