Cracks in oil paintings

[Victor]

I don't know if this is the right place to post this but does anyone know if there is a way to repair fine cracks in an oil painting

Victor....

[Bringer]

Hi Victor,

I suppose that the oils' forum is the best place.
Are you talking about an old painting or a recent one ?
Cracks can be cause by film tension or if the painting is recent from non respected rules of solvent/thinner evaporation between coats and/or fat over lean.
When talking about automotive refinishes, the solution is to sand and repaint, but ofg course that by default I guess that one's not going to follow this method in your case.
Recently I had in my hands a good book about painting restoration.
Just didn't buy it because it was expensive.
To be honest, if it's an old valuable painting, I'd keep an eye on it to see if the cracks develope and if not, wouldn't probably touch it.

Best regards,

José

[Ron Francis]

Hi Victor,
Similar question to the above post ... is it one of your paintings or one you own.
If it is yours then you need to learn what to do to avoid them with your technique, although eventually it will crack as the paint becomes more brittle as it ages.

There isn't really anything that can fix cracks.
If the painting is delaminating, I believe that it can be glued to the back to the canvas or the whole painting could be fixed to another substrate, but that is a conservator's job.
But once there are cracks, I think it is a matter of preserving rather than restoring.

[Victor]

Hi Ron. Jose,

The painting is about 15 years old and not particularly valuable.
It belongs to a fellow artist and he said he thought it would be a matter of using wax but he wasn't sure.
I told him what Jose said and he is going to give it a try. I don't think he has anything to loose

Thanks for your advice

Victor....

[Ron Francis]

Ah!
Wax may disguise the cracks but won't stop it cracking further.
On the other hand, it won't do any damage.

If the cracks are in concentric circles then it is likely that storage (temperature changes) caused the problem, otherwise it was probably his technique in layering his paint without consideration of how much oil is in each layer.
There are other possibilities though ... cheap gesso, overstretched or over keyed canvas, small pigment particle size etc.

[TheBaron]

What type of surface was it painted on would be a valuable piece of information? th painting might have been hung over a fireplace before the oils had dried out completly?

[Victor]

Hi all,
This painting was done on canvas and I don't think it was hung anywhere, just stored.

Victor....

[patindaytona]

Hello,
I have been painting about 4 years using oil. So far, none of my paintings have signs of cracking. I paint many many layers, sometimes using alot of medium (walnut oil), and then other none at all (mixed).
My question is: does signs of cracking usually occur within a time period such as 2-3 years (curing time), due to disregarding fat over lean principle?
And after that I'm pretty safe? I realize that their is a difference between aging cracking, and curing cracking. So if I'm past the curing stage, then I'm safe, i hope. After that, it's a matter of normal aging cracks due to stress, environmental factors (humidity, heat)
Patrick

[sidbledsoe]

Cracking can occur within just about any time frame due to the various different reason(s) for it to happen. Paint thickness varies, binding oils vary, application, types of pigments/paints, storage conditions, etc. I think there is a thread right now in WMO's where someone experienced cracking upon initial drying.
But I think I have heard of others who have seen cracking after months, then some after a year, or many years later, or like the girl with the pearl earring (http://www.flickr.com/photos/nightf3v3r/374415757/in/set-532828/), maybe centuries later.

[sidbledsoe]

I just looked at that closeup of Vermeer again and thought of all the times I have been to museums and closely looked at the cracks in old masters paintings. Then I ask myself, regarding long term cracking issues, do I really want to invest all my efforts in discovering the secrets of the old masters if this is how they have fared? Aside from the prudent practice of following good painting practices that apply to oils, in my opinion the best things one can do to ensure durability and reduce cracking in the long term, is to use linseed oil paints and alkyd mediums.

[Gigalot]

I guess, primer can play first role to crack or not to crack. :) Acrylic primed canvas have no cracks during 50 years, since it was discovered.

[Ron Francis]

Hello,
I have been painting about 4 years using oil. So far, none of my paintings have signs of cracking. I paint many many layers, sometimes using alot of medium (walnut oil), and then other none at all (mixed).
My question is: does signs of cracking usually occur within a time period such as 2-3 years (curing time), due to disregarding fat over lean principle?
And after that I'm pretty safe? I realize that their is a difference between aging cracking, and curing cracking. So if I'm past the curing stage, then I'm safe, i hope. After that, it's a matter of normal aging cracks due to stress, environmental factors (humidity, heat)
Patrick
You have to remember that paint continues to cure over all its life. That is, it becomes more and more brittle until it falls off the canvas.
With in mind, say you painted a fat layer and waited 6 months then painted a lean layer over it.
According to George O'Hanlon from Natural Pigments (via AMIEN), waiting for the underlayer to dry (hard dry) will mitigate the problem to a great degree. However, if both layers keep curing over their lives, eventually the lean layer may overtake the fat layer (even though the fat layer had a head start), and become less flexible and therefore more prone to cracking.
Ralph Mayer expresses thoughts like this in his book although I would be hard pressed to find it at the moment.
Having said that though, I believe that painting lean over fat generally shows cracking fairly quickly after application. A matter of days I think if it is excessive.
Anyway, I would always recommend trying to add at least the same amount of fat to each layer no matter how long the underlayer is left to cure.
Still, 4 years is a good amount of time and an indicator that you shouldn't see any problems for a long time, if at all.

[Gigalot]

There is nothing to be interesting for me "why some painting are cracked or delaminated". Much more interesting is "why some paintings newer cracks?" Why "lean over fat" pastel never can crack? There are nothing more leaner than pastel.
Another good question: How thin or thick paint layer (in nanometers or centimeters) must be to pass "fragile" properties? Why fiber glass armored paint layer do not crack? Why preraphaelites zinc white do not crack? Why Flemish 7-layers still life paintings are still so good after five hundred years?

The cheap industrial paint (housepaint alkyd?) on the street lamppost is not cracked after 20 years it was painted. I guess, those type of paints can stay five hundred years or more at museum conditions.

[patindaytona]

Very interesting discussion here...thanks for the replies. I have oiled out the last 5 or so paintings, only to get them out again and do "just a little touch here"...but it always ends up 5 hours of painting. I'm very obsessive about things.
I have not tried to sell my work since I started painting almost 4 years ago......but.....tomorrow my one piece will be in a showing at the local gallery. They have about 5 or so a year. Maybe I should really think about selling my work instead of worrying about it cracking in 5 or 20 years. They all are so personal to me because of the anquish I put myself thru...but you've got photos of them...and they are just hidden in the closets, anyways.

[patindaytona]

Just thought of something...what if that paint is still just slightly tacky from day before...or even a few days drying. Isn't it still pretty "wet", in spite of it feeling fairly dry? If so........wouldn't that leaner layer over it kind of molecularly bond to it moreso? I understand if it was dry for a month already...that's a little different.

[Ron Francis]

Just thought of something...what if that paint is still just slightly tacky from day before...or even a few days drying. Isn't it still pretty "wet", in spite of it feeling fairly dry? If so........wouldn't that leaner layer over it kind of molecularly bond to it moreso? I understand if it was dry for a month already...that's a little different.
I'm not sure of the chemistry behind that. The newer paint should bond with the tacky paint and form a more of a single layer I guess.
I don't know what would happen when touch dry as paint goes through its greatest dimensional changes in the first few days and if the lean layer dries before the fat layer has done most of its changing then it may be the worst case scenario.

But why would you deliberately want to paint a lean layer over a fat layer?
The bottom line is that you want the outside layers to cure more slowly than the underlayers to create a film with the best chance of longevity.

[patindaytona]

How does a Varnish come into play here? If I varnished after a year or so, wouldn't that somehow hold the paint down? Does that varnish dry the fastest of all those paint layers? That mean it would crack first. What is cracking on Vermeer G.W.Gold earring..the varnish, or that paint beneath?
Clearly, alot of variables in this. I am not doing this intentionally at all. I just end up changing my mind on resuming the painting after I've called it done.
Seems to me that very thick paint would be the worse of all because it would reveal cracks much more and hold more oil content.

[Ron Francis]

Varnish would hold the paint down I suppose, but varnish is meant to be removable when it gets dirty or becomes too yellow etc., so if the paint underneath was delaminating, it would be very difficult to remove the varnish without hurting the painting.
Varnish cracking is another issue.
I believe that modern synthetic varnishes are acrylic and are probably more flexible. I have never used them so I don't really know.
At any rate, if the varnish cracks, it can be removed and re-varnished.
If the paint cracks, the treatment is then to try to stop it cracking any more or less quickly.
Painting thinly is supposed to make a film less likely to crack, yes.

[Gigalot]

Just thought of something...what if that paint is still just slightly tacky from day before...or even a few days drying. Isn't it still pretty "wet", in spite of it feeling fairly dry? If so........wouldn't that leaner layer over it kind of molecularly bond to it moreso? I understand if it was dry for a month already...that's a little different.

Yes, but oil from upper layer can completely penetrate to down layer (sinking effect). And this layer can loose flexibility and, also, do not adhere properly, crack and delaminate.
You need to add natural resin (adhesive) and Alkyd resin (flexible, high molecular weight polymer) to your medium, which can help you to form good paint layer anyway.
Or, do not add alkyds, resin, solvent or wax. Just let your paint layer to dry several weeks and then paint over it safely.