Medium for use with underpaintings

[Anonymous]

The question of solvent only addition is a tricky one. Though the pigment to vehicle ratio remains the same, the dispersion, thickness, and drying rate of the paint film may change significantly. Witness the fact that you must not add too much or the paint film will be rendered underbound. So solvent does change the paint film and it does so in a way that exhibits the earmarks of a leaner paint film, that is, dries faster, and is thinner, and will go through less dimensional changes than a thick oily fat paint film. So effectively in my opinion, it does make it leaner, not by the classic definition of pigment to oil ratio, but by the actual characteristics it imparts. BTW, I know that this opinion/viewpoint is not shared by the gods of Amien but it definitely is shared as being the case by the head chemists at Winsor Newton.

[Trond]

There are so many different opinions about solvents and how they impact FOL. But my understanding is that a solvent, as an ingredient that almost entirely evaporates from the painting, actually does not change the pigment-to-vehicle concentration at all – and that it is the pigment-to-vehicle concentration which is the true measure of fatness or leanness.

I have also heard that…..but it’s not really true in most cases. The reason is simple: most grounds will absorb some of the vehicle. If you dilute the paint with turps, the mix of oil and thinner gets absorbed more easily, and when the remaining turpentine evaporates there is sometimes nothing left to hold the pigment particles. This is why a turpentine wash won’t work very well on true gesso, which is very absorbent; the paint will powder off or crack (I have made this mistake myself). If you apply straight paint from the tube, or diluted it with a little oil, then you can paint straight onto the gesso with no problem.

[llawrence]

Some of that makes sense to me, but I’m not getting all of it. Sid, I had actually asked about chemical changes of solvent on oil earlier somewhere or another (I can’t remember where), but eventually I figured that underbinding was simply caused by spreading the oil and pigment particles so far apart that there effectively just wasn’t a thick enough paint layer to act as an effective binder any longer. What you’re saying, does that mean there’s an actual, permanent chemical change to the binder when solvent is added?

Trond, what you say makes sense as far as it goes – but most painters these days are not painting on traditional gesso, but acrylic primer. I understood that acrylic primer is not all that absorbent. I’m not sure if it would absorb enough of the binder to really make a difference to the ratios we’re talking about.

My website: http://www.rusticportraits.com
My artwork blog: http://llawrencebispo.wordpress.com
My art materials blog: http://sunsikell.wordpress.com

[Trond]

Trond, what you say makes sense as far as it goes – but most painters these days are not painting on traditional gesso, but acrylic primer. I understood that acrylic primer is not all that absorbent. I’m not sure if it would absorb enough of the binder to really make a difference to the ratios we’re talking about.

Exactly. I was not pointing to a general problem, but to the statement that thinning with turps does not change the amount of oil to pigment. Very often it does.

Acrylic primers can also vary though. One brand (Golden?) sells acrylic “primer” and acrylic “gesso”. The “gesso” is very absorbent.

There is one thing I wanted to add: notice that there is very little cracking in De Laszlo’s paintings, but a bit more in those of Sargent, particularly in the dark “wash” areas. Some people here noted that some of Sargent’s painting showed a few cracks even in his lifetime. Sargent quickly laid in his primary turpsy “wash” before continuing with straight paints from the tube, and he painted on oil grounds. The cracking may be due to the oil ground being “fatter” than the wash (and perhaps not always fully cured?). Most of his paintings look quite good today though, and painting straight from the tube is a very archival procedure. De Laszlo also painted on such oil grounds, but he used poppy oil. His medium was therefore very “fat”, and I have a hard time finding cracks in his paintings, other than the ones that have been damaged by other means (e.g. vandalism).

So there are two things that can be tricky with thinning the paints with turpentine or other thinners: the ground could be too absorbent (this one is lethal, conservators say the same), or the ground could, in effect, be “fatter” than your thinned paint. There is an easy fix tough: add a little oil to your turpentine.

[llawrence]

Thanks for the explanation Trond. Seems like every time the subject of FOL comes up, it just keeps getting more and more complex. It’s made me wonder at times if the whole thing isn’t just mythical – or, at least, that there probably aren’t very many painters out there who are actually following it correctly.

With the underbinding thing – luckily for me personally, I just don’t use very much turp any more, even for underpaintings – and what I do use is mixed 50/50 with linseed oil, just like you said.

My website: http://www.rusticportraits.com
My artwork blog: http://llawrencebispo.wordpress.com
My art materials blog: http://sunsikell.wordpress.com

[Anonymous]

I think dave corcoran does a very good job of explaining the underbound aspect when too much solvent is added, in this post here, from one of the numerous threads where this question keeps rearing it’s head over and over again.
I think it is flawed to think of lean paint by the simplistic definition of pigment to oil ratio. I also think the fat over lean axiom is one of the most confusing and trouble making rule of thumbs ever perpetrated on artists. People always try to come up with some simplistic way to categorize a complex process.
As winsor newton says, a better way to think of this is “more flexible over less flexible” now you have all the considerations covered. You want the lower layers to be stable and not shrink before the layer above it does, because if it shrinks underneath a hard stiff layer, then that inflexible layer above it may crack. A film that is thinner and dries faster and contains less thickness of oil (in other words, one diluted with solvent) will reach stability in terms of dimensional changes quicker than the same film with no solvent added. Therefore it looks, acts, and quacks like a lean paint film and not a fatter one.
According to amien, when you add solvent it does not make the paint leaner because it all evaporates and the ratio of pigment to oil is not changed, period, end of story and no more argument. Well I am sorry but it does change the functional performance of the paint film and that is what matters, instead of some myopic rule of thumb about ratio that skirts the rest of the story.

[saintperez]

wow, a whole lot of info to absorb. Wondering if my ground is composted of Utrecht Acrylic gesso the Utrecht oil ground on top of that makes a difference for tooth and absorbency?

Santiago Perez

[Ron Francis]

I don’t think it’s complicated at all!
I agree that we should probably dispense with the axiom “fat over lean”.
I think there are only two things to consider with paint films.

1: As mentioned already, “more flexible over less inflexible” is probably a better way to understand it.
Generally if you add oil to a paint, you are making it more flexible.
If you’re adding solvent, you are not making it more flexible, but as Sid rightly says, you are making it thinner, and thinner layers are less likely to crack (according to Mayer).

But after the paint has gone through its major dimensional changes ultimately it is only the brittleness of the films.

2: “Slower drying over faster drying.” (Outer layers should take longer to dry than underlayers.)
Paint becomes more brittle as it dries, so in this respect it is important to have outer layers take longer to dry than underlayers.
As Sid said, (once again), paint goes through a fairly rapid dimensional change as it dries. From memory it expands and then shrinks.
You don’t want dry paint have paint dry on the surface while the paint underneath is still going through these changes. It would be a little like dry paint on an expanding balloon.
This doesn’t have all that much to do with fat over lean though. If you are using the same oil then I guess the more oil you add, the longer it will take to dry.
But stand oil takes much longer to dry than linseed, so you could have a more oily paint (with linseed) that may dry faster than a less oily one (with stand), all else being equal.
It is better to have a knowledge of the drying attributes of pigments and oils than to try to follow a general fat over lean rule in my opinion.
BUT, you don’t have to be too concerned with this if you let the pant dry enough in the first place before painting over it.

Ron
www.RonaldFrancis.com

[WFMartin]

Just to respond to a few questions and comments that have been asked of me.

I mix up about 2 oz. of my glazing medium recipe, and I store it in a glass bottle, using little bits of it as I need it. It keeps for an eternity, and it does not go stiff, turn brown, or harden in its own storage container as do many alkyd mediums.

In case I haven’t already posted it, here is the recipe I use:

1 part Linseed Oil (Grumbacher or W & N Refined Linseed Oil)
1 part Walnut Oil (M. Graham’s, but not that alkyd-laced stuff)
1 part Venice Turpentine (This is pure, Larch Tree Turpentine (sap–a balsam), and it’s thick as chewing gum. I get mine from Zecchi Art Company in Italy.
2 parts Oil Of Spike Lavender (this is the solvent, and I get mine from Jerry’s Artarama, which offers the best price, by far.)

Not sure why anyone believes that it is not available at Jerry’s because that’s where I get mine, online, and this is the exact page on which it is located. and it is in stock.

http://www.jerrysartarama.com/discount-art-supplies/oil-color-paints-and-mediums/lefranc-and-bourgeois-artists-oil-colors-and-mediums/lefranc-and-bourgeois-extra-fine-oil-color-mediums.htm
That will take you directly to the page, and it will be found near the botton. Extraordinarily fair price, and even with shipping, it comes to less that I can special order it from a local art supply store.

Acrylic gesso or “primer” as it should be termed, is extremely absorbent, and exhibits a lot of “tooth”. That is, it is absorbent if it is behaving like an acrylic primer should behave. That’s what makes the oil paint stick to it, and bond with it.

While it is usually inconvenient to “battle” that absorbency characteristic when applying the first image paint to it, I don’t apply the image paint first. Instead, I apply two coats of Old Holland Cremnitz White paint, tinted with OH Raw Umber, to create a rather light, taffy color. To apply this, I mix it with a medium of 1 part Stand Oil to 5 parts Turpentine. This is an extremely lean medium, but the viscosity of the Stand Oil keeps it a bit viscous, while still being a lean medium.

I allow all the absorbing to happen with this oil ground, which I apply with a 1-inch brush, and allow it to dry before applying yet a second coat.

I avoid acrylic primers which are not porous, nor have some degree of tooth, nor exhibit some degree of absorbency upon the oil paint, merely because to me, absorbency represents good adhesion and bonding of the oil paint. I once tried a sample of Golden Acrylic Gesso, and to me it behaved more like white, acrylic paint, being shiny, glossy, hard, plastic-ey, non-absorbent, very little tooth, and it wouldn’t sand as well. I did not appreciate such an acrylic primer, and I did not use it any further. I use Grumbacher Acrylic Gesso 525, thinned with water to the consistency of cream. I brush it on with a household, sash brush, and I apply anywhere from 4 to 12 extra coats to the usual, store-bought, acrylic-primed canvas, sanding between each 2 coats with 150-grit paper.

Once I have allowed my two coats of White Lead paint to bond with the acrylic primer, I am ready to apply my image oil paint, upon a surface that I consider every bit as good as an expensive, oil-primed surface, but without all the agonizing “curing” time that a true white lead primer must endure.

And, my glazing recipe really represents what I could call a “medium” medium, in terms of fat over lean, being neither “lean” nor “fat”. I use it for each and every layer of my painting, from grisaille, up through and including the uppermost glaze layers of color. The fat over lean principle is not being violated by painting either fat over fat, or lean over lean, because at no point are you ever applying a more brittle layer over a more flexible layer, which is the basic principle behind the fat over lean concept.

wfmartin. My Blog "Creative Realism"...
https://williamfmartin.blogspot.com

[WFMartin]

There are so many different opinions about solvents and how they impact FOL. But my understanding is that a solvent, as an ingredient that almost entirely evaporates from the painting, actually does not change the pigment-to-vehicle concentration at all – and that it is the pigment-to-vehicle concentration which is the true measure of fatness or leanness.

Well, it may not change the concentration, but it most definitely does modify the configuration of it. Using a solvent, alone, as a “medium” may not reduce the amount of oil in the paint, obviously, but it surely does re-arrange the balance and placement of the pigment to the oil within that paint film.

Once the paint dries, it can exhibit a tendency to actually chalk off on your fingertips when rubbed lightly, merely because the solvent has dissolved the oil off the particles of pigment–perhaps not throughout the entire film, but at least on the surface of the paint film, leaving this chalky surface.

wfmartin. My Blog "Creative Realism"...
https://williamfmartin.blogspot.com

[Ron Francis]

Well, it may not change the [I]concentration[/I], but it most definitely does modify the [I]configuration[/I] of it. Using a solvent, alone, as a “medium” may not [I]reduce[/I] the amount of oil in the paint, obviously, but it surely does [I]re-arrange[/I] the balance and placement of the pigment to the oil within that paint film.

Once the paint dries, it can exhibit a tendency to actually chalk off on your fingertips when rubbed lightly, merely because the solvent has dissolved the oil off the particles of pigment–perhaps not throughout the entire film, but at least on the surface of the paint film, leaving this chalky surface.

Yes, this is a classic description of what is referred to as underbound pigment.
To be properly bound, the pigment particles have to be surrounded by oil, and as I understand it, too much solvent washes the oil from around them, possibly making them flocculate.
I think it is a mistake to confuse this with ‘fat over lean’ though as it is a different issue. Common thought is to use no more than 20% solvent.
People use the term ‘lean’ for different things such as a lean medium etc., but what is important in the end is what is left on the canvas.
It really doesn’t matter what you call it, as long as you understand what is going on.

Ron
www.RonaldFrancis.com

[saintperez]

Very interesting and thank you Bill exactly what I was looking for. Ordering from Jerrys now. Had one question though, does anyone have a link to the different properties/ characteristics of different oils (i.e. Walnut, Linsees, Poppy, Spike of Lavendar) etc.

Thanks

Santiago Perez

[DaveGhmn]

….

Not sure why anyone believes that it is not available at Jerry’s because that’s where I get mine, online, and this is the exact page on which it is located. and it is in stock.

[URL]http://www.jerrysartarama.com/discount-art-supplies/oil-color-paints-and-mediums/lefranc-and-bourgeois-artists-oil-colors-and-mediums/lefranc-and-bourgeois-extra-fine-oil-color-mediums.htm[/URL]
….

It’s because the site has faulty subordination. The L&B medium page (and the L&B colors page as well) has accidentally been put under “Genesis Heat Set Paints and Mediums” — and L&B does not appear at all on the landing page for oil colors and mediums.

I’ve sent a note to Jerry’s about the problem.

Judging a Manet from the point of view of Bouguereau, the Manet has not been finished. Judging a Bouguereau from the point of view of Manet, the Bouguereau has not been begun.

--Robert Henri, The Art Spirit

[saintperez]

I actually went to the store down the street from my office and they didn’t have it in physical stock. Ordering online but yes Dave, totally off on their site.

Santiago Perez

[llawrence]

Thanks to all for the explanations and continuing discussion.

BUT, you don’t have to be too concerned with this if you let the pant dry enough in the first place before painting over it.

Yes, this is what I do now, after reading of the soundness of this technique from O’Hanlon. Far, far easier IMO. I don’t have to do any calculations, I can just do a simple test to see if the last layer has finished going through this first oxidation phase or not. Easy peasy.

My website: http://www.rusticportraits.com
My artwork blog: http://llawrencebispo.wordpress.com
My art materials blog: http://sunsikell.wordpress.com

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