Oils cracking and medium question. - Artist Forum
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post #1 of Old 07-02-2018, 09:14 AM Thread Starter
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Unhappy Oils cracking and medium question.


I have been painting with oils for a few years and had never used mediums until recently when someone gave me a bottle a few weeks ago. At that point I wasn't aware of the 'fat over lean' rule and kind of started adding medium to my paint somewhat randomly. Despite this, I did manage to mostly stick to this rule by chance as the first few layers were painted without medium and I have been working up to using washes. However, one of my paintings now has some very light cracking in certain areas. I would like to finish the paintings that have fallen victim to my recklessness. If I paint over the cracked areas using 'fatty' paint and stick to the rules from now on, is it likely that the cracked areas will just keep cracking through the new layers or paint? How long should I leave these paintings before adding new layers so that I can see the full extent of the cracking?

Any advice will be appreciated!
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post #2 of Old 07-04-2018, 03:54 PM
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Picasso loved to see the craquelure develop in his paintings. He thought it belonged in the artistic process. So I don't think you should bother so much. Virtually all the paintings of the Old Masters have cracks in them. Some even use craquelure medium or crack glaze to accomplish this effect.

Anyway, you can without risk paint over an oil layer that is dry. If it has dried for more than 6 months, or so, then you needn't use fat paint, because the paint layer isn't moving much anymore. So you can hide cracks in this way, although not perfectly. Probably, they will sooner or later become visible. But it doesn't matter much. However, the conscientious method is to scrape the paint off and begin anew.

You should always use medium, because the colours become more beautiful, and the paint layer stronger. The traditional medium is linseed oil mixed with solvent, of course. But I recommend some alkyd medium.
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post #3 of Old 07-05-2018, 03:06 AM Thread Starter
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Thanks so much M Winther for taking the time to reply.

I agree with you, the cracks actually don't bother me at all. I find them charming. I think I'm just being paranoid that these paintings would be fragile or 'damaged' or 'un-sellable' as my project is to exhibit them eventually. I didn't know that oil painters should always use medium but you're right, the colours do look so much nicer with it. I will definitely continue but will be more methodical from now on. Someone actually told me recently that too much medium can cause cracking too. Is this true? I recently invested in a 'normal' gloss medium (Sennelier) and a glazing medium for washes. I would also try to try alkyd at some point.

Also, colour quality aside, is it OK to paint without medium or does this lead to quality problems? For example, would a painting done without medium become fragile over time? I've heard mixed responses to this question and would be interested to hear what you think. I have some paintings that I did over two years ago without medium and there is no sign of cracking so far. I worry as I sold a painting last year that was painted without medium. I wouldn't like for the client to have problems with it later on.

Have a lovely day
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post #4 of Old 07-05-2018, 05:52 AM
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It depends on what you mean by "medium". If you use too much solvent, then it might cause flaking, because the binder (linseed oil) becomes too thin. On the other hand, if you use too much linseed oil, then it gives rise to wrinkles in the paint, which is what has happened to Watteau's paintings. But you have to be really careless to create such calamitous effects.

Adding medium cannot cause cracks if it's a good medium, containing both binder and solvent. The only thing that happens is that the paint layer becomes more transparent. It allows light to penetrate the layer and bounce around in there, creating trompe-l'œil effects. Painting directly out of the tube means that the pigment particles are so densely packed that they won't allow light to penetrate. It is also wasteful. You get twice(?) as much paint for the money if you use medium.

The medium in oil paint tubes is sufficient to create a strong paint layer, with one exception. It has always been known that ivory black will start flaking if you don't add medium to it. I made that mistake myself. But all pigments are improved with some medium added to them. It depends also on what brand you use and which pigment. Some already have much binder in them. It is also the question of what artistic impression you want to make. If you want a strong white highlight, then you shouldn't mix it with linseed, as it turns more yellow with time.

However, most artists don't bother much about these things, I imagine. Oil painting is a remarkably durable technique, and all brands are good today, even the cheapest Chinese brands.

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