Fat over lean?

[SSB]

Sorry to bring this up but I been thinking.....

Where did the "fat over lean" come from?

Did the old master's like Rembrandt or others know about the "fat over lean" principle? Did they practice it?

[sidbledsoe]

As i recall, most of the females that remmy painted were rather "rubenesque" as opposed to the twiggy type.

[illastrat]

^lol

if yo don't use this principal your painting will crack. I don't know how many professionals don't paint like this.

[llawrence]

I've wondered this myself, and have done a (no more than perfunctory, so far) search. So far I haven't found any reference to the fat-over-lean principle in any era other than contemporary. If I remain unable to find any older references with a deeper search, it'll be just one more thing that makes me wonder about the rule's validity.

[Kory]

Originally Posted by illastrat

^lol

if yo don't use this principal your painting will crack. I don't know how many professionals don't paint like this.

Yeah, I had never really thought about that, but it makes sense. If you put lean on top, it will dry more quickly than the fat, then when the fat eventually dries, it will contract, and cause the lean on top to pull apart and crack.

[illastrat]

this doesn't mean thick over thin either. Its the amount of solvent you use. It is actually hard to do when employing an impasto technique that some use such as my self because you have to use two different principals at once.. But of course you can exploit this principal if you want to illustrate dried cracky skin or cracked pavement. i've done that before.

[Ron Francis]

Originally Posted by illastrat

this doesn't mean thick over thin either. Its the amount of solvent you use.

There is some debate about the word 'lean' in this context but ...
It's the amount of oil you use rather than the amount of solvent.
Solvent will evaporate, leaving the paint film with the same pigment to oil ratio it had before any solvent was added.
(There is much written here at WC on the subject.)

Interesting question about the history of the fat over lean principle!

[illastrat]

i always thought fat meant more oil. lean meant more solvent. i could be wrong but i doubt. in turn it would be the same as the amount of solvent...turpentine.

[llawrence]

Yeah, I don't think the solvent makes the paint leaner - although there is disagreement about this too, as there is with just about every aspect of FOL.

[illastrat]

i just researched and everything i found said turp = lean

[sidbledsoe]

regardless of the classic strict definition of fat vs lean:
does adding more solvent make a thinner, faster drying paint film than the same paint without the addition of thinner?
Yes.
Is proper painting procedure to paint thick over thin layers?
Yes
Will painting over a layer without solvent addition with a layer that is
solvent diluted violate the more flexible over less flexible principle?
Yes
too much solvent will even make the paint underbound, regardless of the oil to pigment ratio.

[DAK723]

There seem to be two methods of thought on the fat over lean issue. One is how Ron has described - the ratio between oil and pigment. The solvent evaporates and does not play a part in the equation.

The other method is - how much oil is in your paint layer. In this case it is the amount of oil - not the ratio. If your add solvent to your mix - it reduces the amount of oil molecules by spreading them farther apart (to make room for the solvent molecules). So even after the solvent evaporates, your paint layer has less oil molecules then a layer with no solvent added. Therefore, more solvent equals leaner.

Unless you are using a lot of solvent in your mixes, the end result is probably not that different. If you are putting more oil in your mix, it is fatter.

Don

[sidbledsoe]

Where did the "fat over lean" come from?

I have never heard exactly who first said this but the origins of this term was from a time when mediums were mainly vegetable oils or “fats”. Now there are all sorts of solvents and alkyds, etc. that were not under consideration when this rule of thumb was cast in stone. It is not prudent to adhere to antiquated definitions that don't take everything currently used into consideration.
“Fatter” layers are more flexible than “leaner” layers. Therefore each new layer that is applied must be “fatter” than the previous, hence “fat over lean”. When you add a solvent then you will effectively make that paint less flexible and thus in practice it will behave as a leaner paint film and that is important in following this procedure in real life. Amien really ought to know this.

[sarastar]

No not all old masters used these methods. Some let layers dry for months in between and so did not have to worry about this rule. Others did not follow the rule at all and have cracking in their paintings.

Perhaps some masters did not think about the far distant future and care at all if their paintings would last another 20 years or not, I mean most people didn't live past 45, right? Perhaps some painters thinking the world will be over sometime in 2012 might have done terribly fugitive things with their artwork, with no regard for it lasting through the end of the year.

However, if you want your painting to last and not crack in your life time, you should probably follow the simple rules of oil painting.

[Ron Francis]

Sorry Sid, I have to question some of these axioms:

Originally Posted by sidbledsoe

regardless of the classic strict definition of fat vs lean:
does adding more solvent make a thinner, faster drying paint film than the same paint without the addition of thinner?
Yes.

Solvent will allow you to paint thinner, and thinner paint will inherently dry more quickly. I'm not sure that solvent will increase oxidization in any other way.

Is proper painting procedure to paint thick over thin layers?
Yes

I'm not sure where this came from!? Thicker paint doesn't mean that it is more oily. Thicker paint is more likely to wrinkle and crack so I wouldn't call it 'proper' procedure. The principle should be 'more oily over less oily.

Will painting over a layer without solvent addition with a layer that is solvent diluted violate the more flexible over less flexible principle?
Yes

If the oil/pigment ratio in both layers is the same, then both layers will be as flexible as each other. It should make no difference, and in fact, I do it all the time. If you use solvent in a medium, and you are painting onto a layer where the solvent has evaporated, then it is unavoidable.


Illastrat,
Fatter and leaner are confusing terms because they can be used in different ways. A medium with a lot of solvent could be said to be more lean because there is proportionally more solvent in relation to total volume.
But when painting, we should only be concerned with what is left on the canvas. In this regard, in response to a WC member's question, the conservators at AMIEN say:

Solvents play no role in the "rule of fat over lean." They evaporate. It's the amount of oil that counts. End of story.

This discussion can be found here:
http://www.amien.org/forums/showthre...ratio#post9698