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  • Support for Large Scale Egg Tempera PaintingApproveRejectUn-ApproveSubscribeUn-Unsubscribe
    Question asked 2020-01-16 12:15:18 ... Most recent comment 2020-01-22 11:19:35
    Rigid Supports


    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.

    Lora Arbrador

Answers and Comments

  • EditDeleteModerator Answer

    ​Hi Lora

    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: 

    Finally, the above is not the final word on the subject. Other moderators and poster will likely have other ideas and incite.

    Brian Baade
    2020-01-17 13:22:14
  • EditDeleteModerator Answer

    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 paper coating.

    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.

    Brian Baade
    2020-01-17 14:03:57
  • ApproveRejectUn-ApproveUser Comment

    ​Hi Brian and others, Thank you for your detailed responses and I apologize for not reviewing the forum and resources first. I did not understand that I could search the content by keyword but now I do and have!

    Thank you for confirming that tempered hardboard is not only OK but superior to untempered (standard). I read the Ampersand link and was reminded that before I started my previous 4' x 8' panel I had communicated with them about obtaining one of their panels in that size. It turned out that the price of shipping was prohibitive. I also inquired about buying similar panels but could only purchase them in quantities of 100 which would be impossible to store and require several lifetimes to create paintings at my slow painting pace.

    I do carefully cradle my hardboard panels right up to  the edges and champfer the edges prior as Koo recommends. I have been using kiln-dried douglas fir, which although it is technically a soft wood has a very high hardness rating similar to hardwoods. However, based on your resources section I will look for kiln dried oak or maple. I found it curious that in the rigid panel resource section is states that only the bracing on the edges is to be glued. The interior braces should be affixed to the outer bracing using hardware. I assume that is to allow expansion and contraction of the wood, similar to the cradling used on panels constructed from planks of wood (at least the ones on very old paintings.) But perhaps this is unnecessary and I can continue to glue my bracing to the interior of the panel as well as the exterior?

    Getting back to type of panel, I looked into 1/8" plywood (as I am currently using 1/8" hardboard due to weight considerations in a 4' x8' panel). It seems it may be difficult to source high grade 1/8" plywood as most of the airplane grade plywood only comes in smaller sizes. Perhaps you have a source you could share? "Baltic Birch" seems recommended but only comes as large as 5'x5' . Plus in your resource section it recommends maple, walnut or mahogony and not birch as birch may cause more checking. Finally, even if I find a source, due to size, panels are usually shipped by freight which is very expensive. But if I do find a superior panel for my purpose I would be willing to pay in the hundreds but maybe not in the thousands for one panel!!

    So I may need to stay with what I have recently used which is 1/8" hardboard, made from Douglas Fir (which is abundant in the NorthWest.) It is manufactured in Oregon and distributed by the Stimson Company. If I could find a source for 1/8" high grade hardwood plywood, I would then apply a muslim layer as you suggest. And from what I read it would be lighter than the hardboard which would be a real plus.

    I am wondering if aluminum is lighter than hardboard and/or plywood, but at 4'x8' would probably still need bracing, which would add to the weight, and I don't know if hardwood strips would adhere or if metal bracing would be required?

    Best of all, your recommendation that I would NOT need to apply  8 coats of gesso to the rear and could just use the semi-gloss alkyd paint, since I do a pretty good job of bracing. That would make the painting a great deal lighter. Thanks for the link to Koo's question- that helped. 

    BTW, what do you think of the Joseph Edward Southhall substrate for ET? He (or I believe his wife prepared his panels) stretched a loose weave canvas to a wooden frame and then applied equal coats of gesso on either side. The gesso adhered through the loose weave. It seems precarious to me but his paintings seem to hold up with the test of time.

    Thanks so much for this extraordinary forum!!


    2020-01-18 13:10:52
  • EditDeleteModerator Answer

    Hi Lora

    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.

    Brian Baade
    2020-01-18 18:08:22
  • ApproveRejectUn-ApproveUser Comment

    Hello Lora and Brian,

    A few thoughts and questions to add to the conversation. My understanding is the idea of oil migrating up to the surface of a tempered hardboard panel isn't accurate; the oils within tempered hardboard are drying oils, they cure and can't travel within a panel. The presumed problem with a tempered board is more that the oil content makes the surface slightly less absorbent, and thus the gesso doesn't "sink in" and adhere quite as well as on an untempered material.  Still, it adheres well enough, and there is the benefit of greater strength.  So, an untempered board isn't as strong but allows for maximum mechanical adhesion (in my experience, mechanical adhesion is very helpful to long term durability); however a tempered board is a stronger panel (also very important) but with slightly less optimal adhesion.  Is all that correct, Brian?

    I know there are manufacturers who have more experience with ACM (aluminum composite material) panels than I, and hopefully they'll chime in.  For now, here's a bit about my experience.

    I did the cross hatch adhesion test (as outlined by Golden on their website) of traditional gesso atop an ACM panel and had a pretty high failure rate (see photo). KS - Cross Hatch Adhesion TG to ACM.jpeg Attaching fabric first to the surface made a big difference. 

    Regarding how to attach fabric, BEVA is often mentioned as a good option and conservators tend to favor it. However as a practicing artist, it's a bit complicated. The liquid form is quite toxic, I don't want to work with it.  BEVA film takes care of the toxicity, but my experience is that to create a good bond, the temperature needs to be very carefully calibrated, which is hard to do with an iron; air bubbles or imperfect adhesion can result when the temperature is off.  I had my framer use a heat vacuum press to adhere some sheets, which worked better, but that limits the size and adds costs.  Are PVAs and acrylic gels considered durable (albeit irreversible) alternatives for adhering fabric to aluminum?

    I've done maybe half a dozen tempera paintings on ACM at this point, and the results are good but with a few caveats.  First, the drying time of both the gesso (as it's applied) and egg tempera paint is different from on top of wood based supports; in fact, substantially different if the applied layers has lots of water in it (like a thinned glaze or petit lac) - I experienced up to 10 times slower drying times for certain tempera layers atop aluminum. This make sense; the great benefit and drawback of wood based supports is that they act like a sponge.  So if you work with watery paint and/or in a humid climate, expect slower (potentially much slower) drying times (as well as, potentially, more lifting of underlying paint layers as a consequence).

    A hairdryer can help speed things along, but be careful – it can also, if used too often (even on moderate heat), warp an ACM panel (I presume because it's affecting the interior plastic core).

    Finally, ACM panels can definitely develop a bow in them; I had it occur even in a very small panel just from the number of layers of gesso and paint on the front.  And, although rigid, the panels are thin enough that they flex, especially at large sizes, which would be hard on traditional gesso and egg tempera, particularly as ET ages.  I think bracing for large panels is a good idea, although I'm not sure the best way to do this.  

    Kudos to Lora for working on such large scale temperas - most ET painters work relativley small, but you and Botticelli (among others) show us an alternative. 


    2020-01-20 10:15:27
  • EditDeleteModerator Answer

    ​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.

    George O'Hanlon
    2020-01-20 12:40:28
  • EditDeleteModerator Answer

    Koo and George.


    Thanks for weighing in and offering us your experience here.

    Brian Baade
    2020-01-20 12:53:05
  • EditDeleteModerator Answer

    ​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. 

    Mirjam Hintz
    2020-01-22 11:19:35

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