MITRA Forum Question Details

Hi Sarah, 

Thanks for your answer. This is actually not the first time I've spoken to you about paint adhesion. I'm concerned about this because I've noticed my paintings can be exceedingly fragile. There are a lot of different areas on a number of different paintings where I've noticed issues, so for the sake of clarity I'll stick with the most troubling; that is where very simple methods of painting were used and problems still arise.

These are areas where no solvent and no medium is being used, just paint straight from the tube in varying thicknesses.  It's essentially alla prima painting over and over again, each layer given time to dry and the same palette being used throughout.    

Most areas build up enough to lose the weave of a 15 oz (unprimed) canvas.  Some areas are impastoed, some flat. I paint and repaint in many layers, so I thought this would keep the paint lean enough to always be pourous and toothy if I decided another layer was needed.

The surfaces of these layers can range from matte and cakey, course to smooth, to more brittle, shinier impasto. All of these surface types can sometimes seem just as fragile as my more experimental surfaces, where mediums and more questionable techniques are used freely.

Some have been dry for about a year, some a few weeks. It is hard to tell whether additional drying time is the answer. Some passages dried in a week are durable and seemingly similar areas that have been dry for six months are not. They seem weak in the same way. This makes me think a weak bond doesn't always resolve itself. So I'd like to be able to know if a good bond is actually forming, especially if it's primarily a chemical one.

  None have delaminated on their own (probably because the canvas is stretched over panel) but top layers can often be removed fairly easily with a simple piercing and running of the palette knife, peeling off cleanly, a weak, brittle layer (thick or thin) of oil paint from the layer beneath it. It takes about the same amount of force or less that it does to scratch a lottery ticket. Maybe this is normal, I don't know. But it's the separating of layers that is suspicious, as I would think a strong oil painting is bonded all the way through to the ground as one durable film.  Again, some of these layers have had months of drying time.

The ground is a high quality acrylic dispersion made by Utrecht.  I’m now considering going to a lead oil ground to see if it helps, and also switching to using lead white. I've read the films are stronger than titanium and I use a lot of titanium.

What is frustrating is that it seems like lean paint straight from the tube just stops adhering to itself after so many layers, sometimes surprisingly early. I thought this simple method would be fool proof. But maybe a medium is needed at some point in order to ensure adhesion to the previous layer?  I’m very wary of mediums because they can over complicate matters. Also, I've used them by the book before and the same thing is liable to happen, except the area that is poorly bonded is more skin like and flexible than flaky. 

All of this is made more confusing because I don't know what actually constitutes proper bonding between layers and how to recognize it when it's happening. Bonding that would help ensure that the painting will survive well enough under the expected conditions that a painting is meant to endure.  

I do not want to post images online but if you'd like to see some of what I'm talking about, I can send them via email.

Thanks again, I know this was long but I can't tell you how much I appreciate this feedback.

 Thanks, Matthew.  Yeah, I've experienced this with alkyd mediums, as have many artists that I know. I have noticed, however, that some bonds never get better as they dry, or if they do, they improve very little. I’ve noticed it's the bonds that become firm within a week or two that are generally the ones that stay strong, but maybe I'm wrong there.

I've just read some of the basic concepts of commercial paint application. I know they must have different standards, but the concepts of dispersive adhesion such as “wetting”, “roughness” and differing surface energies must apply to oil painting as well, right? If these are universal to all types of painting, is it possible I'm getting air pockets and bridges between lean paint layers that are preventing adhesion?

http://www.materialstoday.com/metal-finishing/features/fundamentals-of-paint-adhesion/

https://en.m.wikipedia.org/wiki/Dispersive_adhesion