Discuss: An Artist Asks: How to fix cracking | BrushBuzz by Canvoo
Discuss: An Artist Asks: How to fix cracking
Submitted by CarrieTurner at 9/10/2010 1:18:34 PM CST
CarrieTurner: I have a potential customer who is looking at a four year old painting that has developed "cracking" or crazing. It is not extensive but I can't sell it as. My question is how do I fix it?
Any suggestions would be appreciated.
Carrie, what medium is it? Oil on canvas? Cracking usually happens when the paint film is diluted too much with solvent or turpentine. Ivory Black cracks, the old - regular alizarin crimson cracks and so do some of the earth colors - because their pigment particles are large and can't be ground down finely.
I'm not sure if you thin your paints, but if you want to thin oil paint, it's better to use a medium to do so instead of solvent. The medium dries as a harder film and has less tendency to crack.
The same thing goes for acrylic. It's better to glaze or thin with medium than with a lot of water because it weakens the pigment binder and the paint can flake later on.
Early cracking can also occur when the painting has been painted on a canvas where the primer hasn't had time to cure properly. Even acrylic should be left for a week or more before one starts painting on it.
The other thing that comes to mind is when the old words of wisdom 'paint lean to fat' are ignored and thin transparent coats of pigment are painted over thicker slower drying layers. Too much solvent e.g turpentine will weaken the paint film and if painted over a thicker layer, especially if it has been mixed with a lot of white it will crack. All oil paint will eventually crack but the above are generally the reasons for early cracking.
I have a similar problem. Yes, lean to fat and all that... I know the traditional technique: first layer thinned with mineral spirit or turpentine, then adding stand oil to the spirit and later optional dammar warnish in the mix. Maybe I didn't wait enough time between layers? I paint very thin and often I paint the whole painting using only odorless turpenoid, because I like the satiny surface. I have cracks on the background on the painting I spent about 100 hours on. QUESTION is: how to fix it? Another painting was in acrylics, I did use water, but not much. Painting cracked in a few places, but only on the one canvas of the diptich. Maybe it's a primer's flaw? Natasha Kinnari
Natasha, turpenoid or other mineral spirits break down the binder in the paint - usually linseed oil, so that there's nothing holding the pigment together after it fully dries... which leads to cracking or flaking.
It's safer to use an oil painting medium to thin paint rather than mineral spirits. The medium further binds the pigment particles and dries to a hard film, whereas mineral spirits like turnpenoid just evaporate. As you're probably aware, there are many formulas for painting mediums. I like Galkyd or Liquin or Walnut Alkyd medium for glazing because they help the paint to dry a bit faster.
Don't know why the acrylic cracked - that's unusual.
Oh, Natasha - I have no idea how to fix a painting that has cracked. The only thing I can think of is to repaint the area - using a painting medium. I did have one painting crack and flake - where I used too much ivory black (which cracks over time), if I were to try to fix it, I would probably lightly sand the cracked area and repaint it with a different color combination. Then when it's dry to the touch, I'd varnish with retouch varnish - probably Kamar... it's a retouch varnish that looks like a final varnish.
final damar varnishes can be applied after an oil painting has dried for 6 months or more. you probably already know that ;-)
Strange that the acrylic cracked? All I can think of is that could happen if it was painted on an oil primed canvas. You can paint oil on acrylic but not acrylic on oil. I can't think of any other reason.
I looked at my acrylic paintings again. It's two paintings 24x24, painted as a diptich, in the same manner, in the same time. The primer is acrylis gesso.The only ONE painting have cracks on it. The paint was thinned to the consistency of a sour cream. I did use masking tape, probably, to create curved lines. As I am new to acrylics and wasn't sure I could do blending, as in oils, I decided to do semi-abstract images with flat areas covered one at a time-between masking tapes. I have painted beautiful matte surfaces with canvas tread visible still. I noticed very thin cracks later, and on the back side there are lines, like someone did with fingernails. I did try to paint over it, the cracks are covered, but the surface looks ugly. The only thing I can do, is to paint over the whole painting part by part (not going to), or create some textures in strategic places to draw attention away from flaws. About oil painting. I paint in oil since 1968, when I entered into my first art college. If you ask any painter, educated in Russia, they will know what is "troichatka", from the word "tri" -three. That mean a mix of turpentine, linseed oil and Damar varnish (or copal, or some other warnish, but damar was the best) . We used so called white spirit instead of turp, because it was hard to get it refined. I suspect, that maybe Damar warnish manufactured in Russia, has some different components, but I never, ever had any problems using it in my mixed medium. Only once I had a painting cracked and I know why: I used too much glue, when sealed my canvas. Once I had the painting painted with thinned damar warnish from the very beginning, and it's still good after 40years. I wish I could post photos with my current cracking problems. Still on another painting oil paint wash went right through the canvas onto the back, like cracks, thought face is OK, but I am sure that the primer is substandard.
I'm not sure if Lori agrees, but I have looked at you website and you know what you are doing and from your description of your paint application nothing is wrong there. I am convinced it is your primer. The paint should never seep thorough to the back. The main object of priming for oil painting is to keep the oil away from the fabric as it turns acid and rots it. Nothing much you can do to fix that other than use it as an experience and check you priming and canvas before you start. The acrylic still has me stumped. Good luck!