Hello,
I’m an oil painter that has had good experiences with using ACM panels with an acrylic dispersion ground as a substrate to paint on. However I noticed some adhesion issues with the last batch of panels I primed and was wondering if anyone has any advice on how to move forward, things to consider etc..
My process for preparing the ground has been as follows;
1) Lighlty scuff/sand the polyester surface of the ACM panel making sure not to sand down to the aluminium surface.
2) Clean the surface with 97% Ethanol
3) Apply a first layer of Golden Acrylic ‘gesso’ mixed with GAC 200 in a ratio of roughly 60/40 – 70/30
4) Leave to dry for 24 hours
5) Apply a second coat of the Acrylic ‘gesso’ with a little bit of water added to improve consistency for easier brushing on the primer. (Max 10% of water) I don’t measure those amounts precisely, doing just by feel.
6) leave to dry for 24 hours
7) Repeat steps 5) and 6) 2 times.
8) Finish the ground with a layer of pure Golden acrylic gesso, no water added.
I live in Belgium and prepared these panels last month when it was pretty cold (wintertime) although the temperatures in my studio were normal room temperature during the day. During the nights it will have beeen colder however, so some temp fluctuation will have occurred. I left the panels to dry for 2 weeks and performed an adhesion test on one of the panels by crosshatching with a blade making little 1/10 inch squares and applying a piece of ducktape and swiftly ripping it off. Result: over 50% of the primer stuck to the tape and came loose…
If I take a palette knife and scratch the side over the delaminated area trying to remove more paint I have to apply some pressure to scratch it off, so there is some amount of bonding but I’m not happy with that result.
How to move forward? Will all of these recently prepared panels be totally unsuitable to paint on? Do I have to worry about more severe delamination of the painted surface in the future? What risks do I take when painting on this surface? Are there ways to improve the current state of the grounds without completely sanding off all of the layers and starting over?
Any advise highly welcomed and appreciated.
Kind regards,
Tom
Dear Matthew,
Thank you for your answer. Any ideas on how to salvage the situation? Is there anything I can do to improve adhesion or do to the panels so to improve the ground for oil painting? It’s a big batch of panels I prepared. Or is there nothing left to do but to reprime the backs of the panels? I added an image of the cross hatch test, showing different types of damage by 3 different sticky tapes. To the far right is the result of the ducktape and some hard palette knife scraping.
Kind regards,
Tom
82B47451-F814-4415-A205-4B5A92655C42.jpeg
Thank you for all your responses! To answer some of the questions posed; as seen in the attached image of my previous comment, the polyester surface of the panel has become visible with the cross hatch/adhesive tape test. So the problem is mostly the adhesion to the acm panel’s surface with the first priming layer. Not an inter layer bonding issue. The reason I applied that number of layers was to create a sufficient barrier between the eventual oil paint film and the substrate. Or is this not necessary? Can the bond between the primer and substrate be weakened by certain painting practices (application of solvent, oil,..etc) ?
Concerning my situation as present. What exactly am I risking by continuing with these panels to paint on with oils? Is the not so good bond between primer and substrate an issue I should be concerned with? What kind of problems may arise further down the line if I were to ignore this? Even though the adhesion is not ideal, the primer is not easily delaminating, I can not peel it off, etc.. so I thought it relevant to ask. Also the paintings are meant for indoor hanging.
Thank you,
Tom
I’m not sure if this is precisely the reason for the poor adhesion described, but since studio temperatures were mentioned: With most acrylic dispersion primers, for a film to achieve the best strength, temperatures should be maintained at 50 degrees F/10 degrees C consistently, including overnight, for several days while the film coalesces to full integrity. (The manufacturer will be the best source for information regarding specific brands, but 50 degrees F is normally the minimum even for architectural/house paints.) If your studio temperatures are dropping below that at night, a tungsten light bulb in a utility lamp might be enough to make a difference, if you can keep one on safely near the primed panels. If you are not able to keep a heat source safely near the panels, it’s best not to schedule priming until warmer times. The first few days after application, while residual water and glycols leave the touch-dry film, is the critical interval.
To the best of my knowledge, if the acrylic film has been affected by cold temperatures, there is no way to improve it after the coating has coalesced. Keep in mind, however, that we don’t know for certain that this is the source of the issue you are describing. Also, I am a studio artist and not a conservation professional so my remarks are just guesses. It does seem to me, however, that the best course of action would be to remove the failed primer and apply a new coat, if it’s obvious that the existing primer is not performing correctly.
Unfortunately, it is very difficult to improve a lack of interlayer adhesion or cohesion on a solid panel covered with a cured acrylic dispersion ground. Additional binder added to the surface would not be able to penetrate through the ground enough to do what you are looking for. Most of it would stay at the top of the ground creating a slicker surface but with little change to the adhesion of the ground.
However, there would be no harm in trying. I just doubt that the results would be what you are hoping for. Repriming may be the only real option. So sorry.
A couple of things to add to the discussion – duct tape is a WAY stronger adhesive than the tape recommended for adhesion tests of architectural coatings. Regular masking tape is much much closer to what is used. Also, did all the layers of the ground delaminate from the panel, or is there a specific layer in-between? It could be that moisture was pulled down with each coat and there was never enough sustained warmth to get full adhesion in the underfyling layers, or to pull out other volatiles within the paint film, so even though the top of the ground might feel dry, there could still be curing happening within an interlayer level lower down. To test for this, it might be good to first take a panel and keep it in a consistently warm and dry environment for several days and retesting. I have definitely seen films that had so-so adhesion at 2-weeks and be quite strong at a month – so 2-weeks is not necessaily the end of the development of adhesion.
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