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Old 22-09-16, 01:22 AM
Koo Schadler's Avatar
Koo Schadler Koo Schadler is offline
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Default Aluminum Panels

Hi Koo,

You mentioned the possibility of using aluminium/aluminum panels. Are they prepared in the same way as mdf? Is an initial sealing with rabbit skin glue necessary or can the gesso mix be applied directly?

Hi Fergus,

Using aluminum as a support for ET was discussed on this forum a few years ago. Jeff Gola used it with success, I believe; probably others have too. Hopefully they will chime in with their experience.

My experience is limited – I’ve made several aluminum panels, but I’ve actually painted on only one so far. I’ve also done a lot of research on the topic, and wrote a handout for students. It’s too long to print the whole thing here, but I’ll paste parts of it in the post that follows.

To cut to the chase, if longevity is a concern, I believe it’s important to first apply linen to aluminum before applying traditional gesso – in my experience traditional gesso applied directly on aluminum failed adhesion tests.

As for the working properties of an aluminum panel, I don't have enough experience to say. I think it depends on an artist’s working method. If you work mostly dry brush it seems to work great. If you apply a lot of water to the surface or many substantial layers (as I do), I think it’s possible to run into problems of moisture accumulating in the gesso, which can encourage paint lifting while trying to accumulate layers, and thus could slow or prevent accumulation of layers.

I also think there are still unanswered durability questions, which I discuss in my handout excerpt. I can hear aluminum enthusiast groan as I raise these concerns…many painters of all mediums love working on aluminum. I’m enthusiastic about it too, but I also like to think long term about these things – art materials can be so full of surprises.

Please let us know if you give it a try, and glad to hear your voice on the forum.

Koo

Last edited by Koo Schadler; 28-09-16 at 02:51 PM.
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Old 22-09-16, 01:30 AM
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Koo Schadler Koo Schadler is offline
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Default

Here are some excerpts from my handout on aluminum panels...

Aluminum remains virtually unaffected by changes in humidity. It creates a lightweight yet rigid and durable support. Oil and acrylic grounds adhere well to aluminum. The question is, does traditional gesso adhere long term? While some people think the answer is an unqualified yes, others are uncertain.

First, a bit about aluminum panels. There are a few companies that sell aluminum panels made exclusively for artists (Trekell ACM panels, Artefex panels from Natural Pigments, aluminum panels from Jacksons, and Duho panels carried by Dick Blick, to name a few). Most sign makers work with aluminum and often have scraps lying around that they are willing to part with.

There are two primary types of aluminum panels:

1. Aluminum Composite Material (ACM) made of aluminum sheets on the exterior with a solid, plastic core. They can be cut to size on a table saw using a carbide tipped or non-ferrous metal blade. ACM panels are what artists mostly work with.

2. Aluminum Honeycomb (AH) panels are made with aluminum sheets on the exterior with a honeycomb, aluminum core. AH panels are thicker and more stable, but heavier and harder to cut due to their thickness.

Preparing the Panel
Aluminum is a highly reactive metal so it’s important the surface be made non-reactive. Most ACM panels are made with a protective coating that prevents reaction, corrosion, etc.

Panels arrive with a removable, plastic film on one side that covers the protective coating - only this side is suitable for gesso. Slowly peel off the film and lightly scuff the surface - do not sand all the way through the coating. Wipe with denatured or rubbing alcohol but do not apply soaps, solvents, or greasy fingerprints, which might affect the coating and/or adhesion of gesso.

Applying Gesso
Given that most ET artists prefer to work on a true gesso, the question is: how well does true gesso adhere to aluminum? This is where things get a bit complicated.

There are primarily two adhesions that occur when gesso is applied to a wood panel: (1) dispersive adhesion, which is most important; and (2) mechanical adhesion, which occurs when gesso soaks into and “interlocks” with the wood grain. When you apply true gesso to a non-absorbent surface, such as aluminum, there is dispersive but no mechanical adhesion. Opinions are mixed on whether this matters.

From both experience and intuition I believe mechanical adhesion is important, particularly if moisture enters into a painting, gets between the gesso and panel, and “breaks” the dispersive adhesion. I recently applied traditional gesso (1) directly on aluminum, and (2) on linen attached to aluminum. Then I tried a “tape pull test” (how the paint industry tests for adhesion). The gesso applied directly to the ACM failed the test; the gesso on linen showed good adhesion.

Given the above, I think if you care about longevity it’s important to first cover the aluminum with cloth, then apply gesso as usual on top. Cloth can be attached with BEVA (a conservators adhesive) or PVA glue; gesso is then applied directly over the cloth. (FYI, Trekell makes ACM panels already covered with linen, attached using BEVA).

An aluminum panel covered in true gesso creates a lightweight, stable support that is seemingly ideal in the short term. But will it change the working properties of egg tempera paint, and how does it endure over time? No extensive painting or long-term aging studies of true gesso and egg tempera on aluminum have been undertaken at this point, as far as I know. A few possible questions are:

- At times the water content in egg tempera paint is significant, particularly when a “petit lac” (“little lake”) is applied. In my experience (admittedly minimal) in making aluminum panels, I found gesso dries much more slowly atop aluminum than on wood, presumably because of the non-porous metal under the gesso. Would the same thing happen with water-rich paint? Might excess moisture in the ground cause problems to the ground, paint layers, working properties or drying time of the paint?

-Atmospheric humidity is always traveling in and out of a painting to varying degrees. A wood panel soaks up moisture, which is problematic because it causes the wood to move. It also means that moisture entering a painting has somewhere to go - into the wood! An aluminum panel itself doesn't absorb moisture, but nonetheless a small amount of humidity enters from the front of the painting into the paint layers. Where does it go? Does it sit atop the aluminum, encouraging delamination between support and ground? Is additional moisture created by condensation on metal, particularly if a painting sits in a heated room against a cool, outer wall?

- Wood’s absorbency also might help with “Fatty Acid Migration” (FAM), a type of efflorescence that can occur in egg tempera (and occasionally oil) paintings. If a paint film has too much binder (yolk) in it, extra lipids migrate to a painting’s surface and create a whitish “fuzz” (which, in most cases, can be carefully wiped off without harming the painting). FAM is not a well-understood phenomenon, but some conservators suspect that a wood support helps absorb excess lipids and thus mitigates FAM. Would aluminum panels increase FAM?

Aluminum panels have great promise, but at this point have no long-term history with true gesso and egg tempera. Paintings are fragile objects, and many collectors (unknowingly) don't treat artwork well. If a tempera painting on an aluminum panel experienced problems at some point, an unhappy collector might question the use of non-traditional materials that could be seen as untested. Damaged paintings go to conservators who might, rightly or wrongly, look askance at an aluminum support.

For now, I am reluctant to switch to aluminum. The risks involved in using wood panels, and how to mitigate those risks, are known. For better and for worse, wood is the conservative choice. Despite this hesitation I am interested in aluminum as a support for ET and hope that artists continue to experiment (as I will). If you’ve tried ACM, please let us know the results (both short and long term).

Last edited by Koo Schadler; 24-09-16 at 05:17 PM.
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