MITRA Forum Question Details

  Hi Jesus, i am not sure why you really interest to try metal panel that i actually had concerns with. the issue is for metal its expansion rate is very high, that may result of cracking in temp. changes. also the adhesion of ground to metal may be weak, because the surface is not porous for best adhesion. 

plus it is only a very thin metal sheet, glues on a core, usually a plastic type, so i think it had risk of delamination or bending. and it could be very heavy. 

so what i think a better alternative is tempered hardboard, which is engineered wood that immerged in oil for tempering, result of a stronger structure. 

and i also not like gluing canvas on substrate, the reason is because with moisture fluation the canvas will experence dimension changes, that may lead to cracking.

​so it would be best to directly acrylic gesso on tempered hardboard, it will result a very simple structure. 

Hi, ​thank you for your answer. The first concern you mentioned i​s indeed the one that made me rule out anodized aluminum to begin with. 

If using ACM panels my take would be glueing them to a metalic craddle to prevent bending, and using an ACM already coated with a polyester fabric, to promote adhession. If glueing a top fabric, it would be a polyester one, which being synthetic doesn't react to changes in RH, preventing the oil painting layers from being exposed to potential damage. Having read a lot of opinions in this forum in favour of this solution, I have got truly interested in this option, hence my seek for advice. 

​I eitherway want to try an Ampersand tempered gessoboard (a brand for tempered hardboard) as well, but I think an Alucobond coated with polyester could be a good option just as Mr. Merrill stated back in the early 2000s.

hi, the thing is for metal panel you had to worry the adhesion of your polyester coating. even it is manufacture do that for you, it still has risk of being delamination due to the natural of metal surface. think about how easy a car paint can peel off from its metal. 

and these product had not developed for archival purpose to use in mind, so not see a good reason to use them. 

also, metal will expand much more than oil layer, that will result a cracking, even your polyest is inert to RH. but metal is sensitive to temp change. 

but wood substrate had been used in hisotry and is proven to last. and engineered wood trying to solve common wood issue. 

​and tempered hardboard is porous to accept bonding to acrylic gesso, that i had take a test to apply acrylic gesso on top and use a knife to scrap it, and found it aheres wood layer off, so it means it really bonds. 

​Hi, thank you again for your reply. I understand your statement. I have read a lot of information regarding that substarte, and some people still are doubtful on that substrate as well. It could be possible, though, to glue the polyester fabric onto a tempered hardboard.

The main problem then is tempered or untempered hardboard availabilty here in Spain, as MDF is mainly the only wood substrate of this kind I have been able to find so far. 

I can find them through Jackson's, which ships here, but also a problemartic is size: there are artworks I want to create that would be 2 meters in size, which would be too heavy for a wooden panel to not suffer planar deformation, an also even harder to find. I don't know if Ampersand creates, and much less ships, such panel sizes. 

​Ahh if only a truly archival, synthetic support were readily available... 

hi, i not sure why you want to glue polyester fabric on any substrate? it is okay to glue but my concern is the fabric pattern on polyester is too mechanical that these regular pattern shows on the picture looks not natural. also i experienced a cracking of polyester canvas before. 

​and for tempered hardboard, you no need to buy from art store, it is commonly available construction material in lumberyard, so you just go there can buy a very large size and cut to what you need. it is exactly the samething you will order from art store but charges you 20X more! 

r​

​About the fabric you are correct, although my plan was to cover the patter with a slightly thick lead oil ground on top of the acrilyc gesso. 

I can ask in a wood store I know here. Also, I have read the tempered ones are less desirable than untempered, as the former accepts more readily the acrylic gesso, bonds better, according a few opinions in this forum. 

​Still wood's sensitivity to RH, temperature and bugs are something that concern me...

hi, Lead oil ground is a traditional type of ground, with the lead that makes it dries fast, lean and relative flexible. however it is still has the same property of drying oil, which is less flexible compared to acrylic and suspect of cracking during age, where acrylic will not crack over time. and when you make it thick, it will be fatter, oilly and more suspect of cracking. usually oil ground is applied in relatively thinner layer. 

some people still prefer lead oil ground but i think acrylic is a good alternative of modern material. 

you are correct to read people concerns about tempered hardboard, and i actually did a test myself that apply acrylic gesso on tempered, and using a knife to scrap it off, and found it always peels off a thin wood layer off, which means it is very good adhesion. 

​untempered is hard to find in store because its structure is not very rigid compared with tempered one. and since it is tempered, it is less subject to environmental changes. and of course, you best to apply isolation layer all around, maybe a varnish or wood sealant like shellac. i personally using the same picture varnish all around the wood panel. 

take your own test and you should love it. ​

​These a fair points indeed. I will test it, definitelly.

​About the lead oil ground, I think maybe, no matter the support, it would be an option to apply it in thin layers as you mentioned on top of an acrylic gesso. I am not too fond of painting directly with oils on acrylic gesso, the feel of it is not something I like too much. Would it be a sound practice?

Hi, no need to worry about oil on acrylic as it is proven of good adhesion. i mean even you apply oil ground, then what you put underneath is still acrylic sealer, unless you use rabbit skin glue. 

​i had seen delamination of coating on metal support in some cases. but anyway, they are designed for outdoor display, which doesnt really have requirement of hundered years achivability. but i mean it could work for you, just feel it is very expensive for large size. 

so i think get tempered hardboard from your lumberyard, you will get a cheap but achival surface after you apply acrylic gesso on top. 

Hello Greg, thank you so much for your reply. I am glad to read that both ACM and tempered hardboard are considered to be good alternatives if coated with acrylic gesso and then oil ground. After mulling it over, I think both are almost equal in terms of stability. I think I will have to give them both a try to make my final decission. 

Another question about the fabric weave being visible, I am curious, would it be a good approach then to cover the polyester fabric with 3-4 layers of acrylic gesso (with in between layers sanding) to cover the fabric's pattern, and then applying the oil ground on that flatter acrylic surface, in case I go for the polyester glued ACM? I would love to do so, as if there in one thing I am sure is that I can't stand the fabric weave being visible in the actual final painting. If so, i think I would try to go for this option first, as the weight of a craddled tempered hardboard would be quite troublesome to deal with for 1,5-2 meters paintings.

​Also, this question is for anyone who may know. I have already received a few samples of Sunbrella fabric (recommended by Ross Merrill as possibly the best option for painting on ppolyester), but I am still doubtful on how to remove the hidrophobic coating applied on it. It would be interesting to remove it to enhance acrylic gesso adhesion. I asked Sunbrella, but they couldn't tell me a specific way to get rid of it. So far I have just figured out this is a fluorocarbon finish​. If anyone can chime in on how to safely remove it, I would be truly grateful.  

Kind regards, 

Jesus

Hello Greg, thank you so much for your thorough explanation. I had never heard of Molding Pastes before, but they definitely seem to be the solution to my concern. 

May I ask, for the sake of learning, what is the difference between them and acrylic gesso? I imagine that they are safe and equally archival compared to acrylic gessos, but I want to specifically ask on their compositional difference. 

​As for the fabrics, I have already spotted a website from UK which sells Fredrix's 100% polyester canvases, which is a relief being located in Europe. I will try to get some soon and start testing them, can't wait. ​

Kind regards,

Jesús

hi Jesús,

​i am very courious that since you already used hard sustrate, then why you still want to glue fabric canvas but to even out fabric texture, rather than painting on hard substrate directly? 

usually people who prefer to paint on fabric is because they like the wavy pattern that grabs their paint in the way they like the friction and it holds up thicker paints. 

but i see you want to even out the texture using thick acrylic medium. first if you paint directly on hard substrate like your metal panel or tempered hardboard, it is already a smooth surface without wavy pattern. second, the key for anything is to apply thinnly, if it is thick, it will had risk of cracking, so to even out the wavy pattern, probably is time consuming and i am not really see any benefit of doing so. ​

​​​Hi. thank you both for your replies. 

To the first reply (apologies, I can't see your name), my interest in a mounted canvas is twofold:

First, I am concerned about directly painting on the ACM panel as I am dubious on how good the adhesrence of gesso and paint will be over time. In the resources PDFs XIM-UMA or DTM bonding primers are adviced to apply after sanding the polyester coating of the panel to improved adherence of the posterior gesso layers. Apart from not liking the fact of using industrial ​products not meant for fine arts, I can't get them here in Europe, so that's another problem added. I can get Zinsser Bulls Eye, but still, industrial product, SID or failure of the primer could happen in the future. 

Maybe that's not a problem, or ​perhaps I can safely paint on an ACM after sanding the polyester coating and applying a few layers of acrylic gesso, but I worry about the lifespan of that process. 

The second reason is reversibility: both hardboards and ACM panels suffer from the same, the concern of breaking corners and the impossibility to fix them. So having the painting resting in a canvas mounted to the panels seems to be a good precaution, just in case. I certainly agree with you though, the extra steps of adding the molding paste are tedious, but unless I am wrong in my previous statements, these are my reasons. Of course, anyone is welcome to chime in and tell me otherwise, I am open minded, and the simplest approach would be the most desirable, in the end.

Again, thank you so much for the information, Greg. I have been told by Michael Skalka himself to size and then apply a few acrylic gesso coats to prepare the fabric before any oil application. How would this process be best adapted in case of adding the molding paste in the recipe, after the sizing? 

I understand then that the molding paste is also an archival product. Regarding acrylic gessos, I have read good reviews of Lascaux, still have to get some to try. Any other molding paste and gesso you would recommend to check?

​Thank you so much for your time, I appreciate a lot all the information I am learning here.

Hi Jesus,

​you are more than welcome and your concern is reasonable, however here is actually my thoughts. if you using tempered hardboard, you should not worry about long term adhesion of acrylic ground or your oil grounds. as it is still a wood but engineered one and wood is a proven substrate in history. 

and you can cradel it up to protect the corners, once it well protect, it is not easily to beak there. 

or another tip is you always paint smaller than the panel size, because when you frame it, the frame also covers a portion, and if you do so, you wont worry about any corner breakage and even break, it is easy to fix by wood work. 

i was also trying to glue canvas before, but i found problem of doing so. the glue or acrylic product is relatively too thin for the coarse side of fabric, so i found some area is unglued after a time, maybe got absorbed by the fabric, so it turns out a partial glued canvas. 

in addition, it is not really reversible as we think, because the glue is permenant actually.

so after these test, i end up painting directly on it. 

but plz do your own test and try all the options and maybe comeback here to share your experient result as well! 

looking forward! 

That's exactly the reason why I will try to find and test a tempered hardboard as you suggest. I am yet to find a place were to confirm availability and quality here, but at least for the sake of learning, It's worth the effort. It would though be a problem with larger panels (some paintings of mine are going to reach 2 meters, hence my interest on craddled ACM for the light weight, will have to weigh options in those scenarios). 

You actually have a great point with regards of the smaller than the support painting, hilarious how the fact a tiny part of the picture is going to be covered by ​the frame had completely skipped my mind. In that case, in fact, I am less worried on the margins even if painting towards the end (a couple cms would be of no importance for any of my pictures, so it can be both hidden by the frame or/and removed if damaged in the future). 

Gluing a canvas would indeed​ require a proper system/process to properly do it. However, my idea would be to use a conservation thermoset glue​, like Beba 371 or Jade. If I am correct, both can be activated again with heat, so any imprfection can be corrected, and can be separated from the support if necessary. I would never go for a permanent support, specially before the possible scenario you mentioned, having badly glued spots here and there. 

I will definitely check and test both options, and hope to find the best option and share it with you all. I am a bit obssesive in such topics, and want to make a final decission this year already. 

​​​Kind regards!

​​Hi, quick update: here in Spain neither tempered nor untempered hardboard exist, nobody in any main lumberyard​ here in Madrid knew what I was talking about, so seemingly I will have to stick to ACM for the asdhession tests and the large artworks I want to do, importing large hardboard panels from abroad is simply crazy and wouldn't be affordable. 

I will start testing adhesion in a Dibond plate I have got, crossing fingers.​

Kind regards, 

Jesus

Someone in this thread posted that metal expands and shrinks more than wood products. That is the opposite of the chart I saw. It showed that aluminum is more stable than any kind of wood except perhaps the finest quality hardwood that has been cut the correct (and rare) way. That wood requires old growth hardwood trees so it's typically not environmentally friendly. It's also heavy and expensive.

I don't recommend anything other than aluminum based on everything I have read. I especially would avoid plywood and other processed wood products.

— SRS​