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Question asked 2020-01-16 12:15:18 ...
Most recent comment 2020-01-22 11:19:35
I reviewed prior questions and comments in the "rigid support" forum before posing my question. I've been using 1/8" hardboard, cradled approximately every 12" with kiln-dried douglas fir 1" x 2" stripping. This seems to work fine. I do apply 8 coats of traditional gesso front and back, finishing with one coat of alkyd paint on rear per Koo Schadler's instructions.
My main issue is weight. On a 4' x 8' panel this becomes very heavy. I need the help of a friend to move it at all.
Is there a lighter weight material that I could safely try? I wrote to Simon Liu but he says his panels are not safe for traditional gesso.
What about coroplast, or an archival foamcore type material? I could still cradle it with wooden strips for rigidity and would be willing to glue a muslim layer on. Any ideas for lighter weight materials?
An advantage of my system is, of course, that it is dirt cheap but i would be willing to pay quite a bit more for a lighter weight solution.
Two other issues:
1. It is almost gospel that we are to use untempered (standard) hardboard, but I've heard from manufacturers that the amount of oil or resin in modern hardboard is miniscule and actually adds to the integrity of the board, as untempered does tend to chip more at the edges. Perhaps at this point it is just myth that the oil will migrate through to the gesso and affect the painting? For a long time I could not source untempered hardboard in California except by ordering 100 sheets shipped by freight. But now I can buy it locally but I'm wondering if tempered may actually be better?
2. The logic behind applying equal number of coats of gesso, front and back is to equalize the forces in order to prevent warpage. However, the hardboard that is available to me has a "screen back" so it absorbs more gesso. Plus the rear has cradling which also affects the amount of gesso, so is perhaps appling equal coats no longer necessary or, in fact, should I be quantifying the amount of gesso applied either by weight or volume to ensure that the amount is equal on front and rear?
That's it! Thanks so much. It is comfortaing and amazing to have this in-depth MITRA forum available to us artists.
Answers and Comments
Here are a few on my thoughts on this subject
1. Today, tempered hardboard is superior to untampered for this purpose. Additionally, not all hardboards are equal even if one is comparing a sample of one manufacturer's tempered board with one from another company. This PDF from Amperstand is a useful read:
2. I personally do not like hardboards as painting substrates unless they are surrounded by a hardwood surrounded like a frame. It is just too easy to accidently hit the corner of the panel and have it permanently bumped/expanded. Hardboards are also heavy, as you state.
3. I would not recommend applying gesso to fomecore or chloroplast. The fomecore is just not stable enough in any direction and is easily punctured. We generally want the substrate to be more rigid than the priming and paint layers. I have never experimented with putting grounds on Chloroplast and, therefore, cannot recommend it.
4. Many artists like to use thin birch ply as a support for gesso and acrylic dispersion grounds. I do not recommend these as the ground invariably develops checks along the grain lines. A search in our rigid supports section will reveal a number of threads on this subject. However, you can glue a fine fabric to the cradle lightweight ply. This mitigates most of the problems with checking. Again, this has been discussed many times here including suitable adhesives, etc.. A gessoed braced panel made from lightweight birch or other quality ply would likely be lighter than the hardboard panels you are used to.
5. Aluminum composite boards may eventually be the solution for those looking for a rigid stable panel that does not have a grain and does not respond greatly to changes in the environment. I believe that this is still in the testing phase but I will reach out to other moderators to see what the current state of ACM panels also require a fabric interlayer before an animal glue bound ground can be applied.
6. It is a great idea to apply an equal number of layers to the front and back. I do think that you may be over thinking this and just adding a equal number should be sufficient. If you have a well cradled/braced panel you many not need to apply gesso to the back at all. In fact, the bracing makes this difficult anyway. I would probably paint the back of the panel and bracing. Take a look at this thread:https://www.artcons.udel.edu/mitra/forums/question?QID=431
Finally, the above is not the final word on the subject. Other moderators and poster will likely have other ideas and incite.
I just remembered many years ago that I worked with another
painting conservator to help them come up with the protocol to treat a group of egg tempera paintings on fomecore. The paint was literally scaling off in
sheets. The artist did not apply a ground so the tempera was directly on the
I would think that applying an animal glue ground to
fomecore would severely distort the substrate as it does not have enough
rigidity on its own to counteract the surface tension resultant form the drying
of the glue. I would not think that even coating the reverse would remedy this.
If you decide to test this out let us know the results. I would not change my
mind as to the suitability of fomecore either way, though.
When I wrote to not adhere the interior bracing, I guess
that I did not make myself clear. I meant that, in the best-case scenario, the
interior bracing should not be adhered to the back of the panel, but only to
the outside bracing. The outside bracing would be adhered to the panel. My
thinking for this is that the job of the interior bracing is performed as long
as it is strongly connected to the
outside bracing, even if it is not glued to the panel. On the other hand, I
have seen panels where the glue-on interior bracing caused slight buckling to
the panel corresponding to the placement of the bracing. This is really not a
huge issue, it does not happen to most panels prepared this way, and the
buckling is not pronounced anyway.
I was unaware of Joseph Edward Southhall substrate preparation
for egg tempera. I can see no benefit for the method as compared to pre-adhering
the fabric. It would seem to just add another possible vector for failure.
We have had good success with applying traditional gesso or chalk grounds to aluminum composite material (ACM). The only issue we found with applying it directly to ACM is that adhesion can be good to poor depending upon the application. To mitigate the variability of adhesion, we have applied a coating of animal coolage glue and then a lightweight, open weave fabric adhered with the same glue. The ground can then be applied over the fabric with excellent adhesion.
Koo and George.
Thanks for weighing in and offering us your experience here.
If they weren't so expensive than honeycomb panels as they are used in air crafts should work as they offer the necessary rigidity and light weight.
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