Oiling Out and the Cause of Dead Spots in Oil Paintings

Hello Sarah, good morning. I came across the problem of dead dry patches when applied linseed oil to my finished painting before varnishing. I see a few dry patches that do not get leveling shinning as most of the painting seems leveled with oiling out. My question is how to fix this problem before I apply varnish. 2nd question, how long do I have to wait before applying varnish after this application of linseed oil used as oiling out process?

A: It is not something we can approve or recommend, and we know that no conservator or materials expert would present this as best practice. So thats the short answer. That said, if having to use something, then a retouch varnish would be better than a general oiling out since it is at least potentially removable and should not yellow appreciably if art all. So if you have to do something, that would be the best option in our opinion.

Your ground may be too absorbent. Try experimenting with different grounds to see if this helps prevent your oil paints from sinking in.

On absorbent surfaces the Stand Oil generally did better than the more fluid alkyd medium, its thicker consistency allowing for better hold-out and resistance to soaking in. However the Stand Oil, as expected, also dried more slowly.

Q: Or, is the long term problem caused by the fact that a layer of oil (regardless of type) will attract dirt which will cause it to yellow, and it wont be removable as a varnish would be?

Its been a problem for a very long time. At least according to the historical record. Blotchiness. Sinking in. Dead spots. For oil painters these are well known terms, conjuring up images of skin disease as much as painted surfaces, but whatever words are used the implication is clear its an undesirable nuisance;  a loathsome interloper in the creative process.

This can take patience and try nerves, but if experiencing dead areas after a painting is finished the best thing would be to wait for it to dry sufficiently to allow for a final varnish. Waiting 6-12 months remains the safe rule before varnishing, and while there are some who advocate a shorter period, we feel there has not been enough research done on the possible consequences. That said, if needing to apply something earlier, after making sure it is at least hard dry, the use of a proper retouch varnish would be preferable. These are typically composed of thinned-down versions of full strength varnishes and should be applied as thinly as possible, aiming to simply create an even overall sheen. Damar and other natural resin varnishes should not be used for this purpose due to yellowing and embrittlement.

Oiling Out and the Cause of Dead Spots in Oil Paintings

Before heading toward causes and cures its good to briefly define the problem, especially if this issue is new to you. What is being described here is the appearance of a dull matte area in a section of an oil painting. Thus the sense that the color has sunken-in, or gone dead. This is particularly annoying with darker colors, where their matte appearance makes them seem lighter and creates the problem of matching a color with fresh, glossier paint much more difficult (Image 1).

Thanks Sarah as usual you go the extra mile! Enjoy your time in Peru, because I will be bugging you again after June 6! Regards.

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Image 5: Different sheens caused by film thickness on oil grounds. Cobalt Blue Deep and Raw Umber.(Click image for higher resolution)

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You are using paint with a high pigment to binder ratio. Some paint formulations may inherently have a low concentration of binder. Try adding a touch of oil medium to your paints to help maintain sheen and body.

Or take a look at the varnishes put out by such companies as Gamblin, Natural Pigments, or Winsor Newton as all of these would be possibilities.

Image 8: Raw Umber and Phthalo Green on Three Coats of GOLDEN Absorbent Ground(Click image for higher resolution)

Thanks for the warm words about the article we truly appreciate it! And great questions which I try to answer below:

Hi Meera. Thanks for the great questions. As you can sense in our article, we recommend oiling out only when needing to alter the sheen of an area one will be painting back into and never as a final finish on its own. In terms of evening things out once a painting is done, one of the uses of varnishing is just that to unify the sheen over the painting, and so one would typically just apply sufficient varnish to achieve that or, if needed, to start with a light spot application of varnish to a sunken in area and then follow with a more overall application. Finally, in terms of how long to wait, we take a very conservative approach and recommend always waiting 6-12 months after the last layers are applied including things like oiling out. If you do not have that luxury of time, then we would obviously encourage you to wait as long as possible, with perhaps a month being a good minimum. But sadly there is not enough testing around this to be precise. Using retouch varnish will also help limit issues of applying varnish early on, so would agree that is the better option.

Thank you for doing this study . I have a painting with dark dead areas right now, but I still love the painting.Waiting for it to dry and varnish will fix it.

In general, oiling out is not recommended. However, if you choose to oil out your painting we recommend you follow the steps outlined in the Best Practices section below. If you are finding that you frequently need to oil out your painting it is best to consider the following factors that are likely at the root of the problem:

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In feel and performance these come closest to various traditional absorbent grounds, such as chalk gesso. In all applications Raw Umber had areas that were sunken-in, especially where wiped away or thinned with solvent. It clearly did best when Stand Oil was added. Phthalo Green, on the other hand, did okay not as well as elsewhere, but clearly able to hold onto some luster and, with added mediums, able to maintain a glossy sheen even in a thin glaze. 

Please note, while included in these tests, the Absorbent Ground Tech Sheet cautions against the use of full-bodied oil paint applications as the extremely porous surface can absorb too much binder, leaving the paint sunken in or, at worse, underbound. (Images 8 & 9)

Some paint colors are notorious for being dull, so now I know what to do with Stand Oil.

Image 6: Raw Umber and Phthalo Green on Two Coats of GOLDEN Acrylic Gesso(Click image for higher resolution)

Image 10: Raw Umber and Phthalo Green on Two Coats of WIlliamsburg Lead Oil Ground(Click image for higher resolution)

Hope that helps. If you need more assistance I will be back on June 6th.

A third cause needs to be mentioned, which functions independently of a grounds particular absorbency; namely film thickness. For many paints, it turns out this alone is enough to cause a matte appearance to develop, as you can see in the following examples.

In the past it was common to deal with this problem through the use of retouch varnishes or various recipes for mediums that were applied in order to resaturate the matte areas and help with color matching when starting to paint again. Unfortunately these were often extended over the entire painting, creating issues later on for conservators as these layers would yellow badly as they aged and, in the case of varnish, grow brittle and remain sensitive to solvents. In light of that, current recommendations are much more targeted and simple.

As for fast drying mediums, oil painting is ultimately a medium that rewards patience and taking shortcuts almost always entails a lot of additional risks. That said, something based on Stand Oil with an alkyd to help speed drying, and OMS if needed, is perhaps the best I can offer.

A: Yes to all of these things.As the article points out, one should oil out ONLY in areas you plan to paint back into, and not as a continuous overall coating left alone. Obviously when painting on top of an oiled out section, these other issues are not a factor.

Overall our philosophy is to keep things as simple as possible and avoid as many intervening layers of oil or even worse, varnish as possible. But art is always at least partly a dialog and tug-of-war between artistic necessity and technical soundness.

Overall, whileslightlymore absorbent than the various oil grounds, the wordslightlyneeds to be emphasized. Neither application was anywhere near the extreme absorbency conjured up by so many on forums and discussion boards. That said, these tests only included our own brand, and sadly acrylic gessoes have become a category with a notoriously broad spectrum of quality and performance in the marketplace, with many being overly absorbent and even brittle due to excessive amounts of fillers and water. 

In the results, 4 coats did better than 2, feeling less absorbent and performing closer to an oil ground. However, wiping paint away was not as easy as with oil grounds, something that is frequently noted.  (Images 6 & 7)

Curious to hear your thoughts. Thank you

Image 9: Raw Umber and Phthalo Green on Two Coats of GOLDEN Acrylic Ground for Pastels(Click image for higher resolution)

If the painting is fully cured final varnishing should help to even out the sheen and fix any sunken-in passages. After all, retouch varnish, which has its own long history of use as a curative for sinking-in, is simply a weakened, dilute solution of a full strength varnish. So the practice of using varnishes to fix this issue is a well known, traditional approach. It is also important to always start with thin layers of gloss varnish until an overall even sheen is established, and one might need to start with a thin application on just those areas with dramatic sinking-in for a more even final result. Lastly, we think its important for the painting to have ideally dried for the traditional 6-12 month period to assure that it is no longer undergoing many changes and has become hard dry.

Great article, but now I am totally confused on best practice. Based on your research it shows oiling out is bad, so that makes me wonder why would a company like Gamblin advocate to oil out for every painting?

Q: What do you think of oiling out sunken areas with safflower (with or without a little alkyd in it), even if Im not going to repaint those areas, and then varnishing later when the time is right?

Thanks so much for this insightful article. The darker areas of my painting developed a cloudy and matte appearance. I believe the colors have sunken in. The color was a rich dark brown (mixture of Ivory Black, Rublev Purple Ocher, Yellow Ochre Deep and I think English Red), and I thinned it with refined linseed oil to create a thin layer for my shadows. After reading your article, I think the thin layer may have been the source of the problem.

Image 3: Connection of film thickness and sheen on non-absorbent film. Raw Umber and Phthalo Green.(Click image for higher resolution)

As for what to do about it, the traditional and handed down remedies have run the gamut from oiling out with different recipes to the frequent application of retouch varnishes of various types. What is the current thinking about all this? What might be the cause and best solution? What follows is not an exhaustive treatment on this topic by any means, but it shares results from some current testing and offers what we feel are best practices given what is currently known.

When repainting is not possible or practical, one can apply a small amount of a drying oilonlyto an area you plan to work into, making sure to wipe off any excess. Preferably use the same oil or medium found in the paints or in that section, applying as little as possible and using only enough to even out the sheen.Neverextend this treatment to the painting as a whole, or to areas that will not be painted over in that days session. Doing so can create problems with adhesion and the eventual darkening and yellowing of those areas.

Adding solvent to the oil to create a thinner application, or thinning something more viscous like Stand Oil, is possible but care must be taken as young oil films can remain solvent sensitive, especially when underbound. In addition, solvents can extract materials from the film and make it more brittle over time.

Hope that helps and if there is anything else we can do, just ask! Also, feel free to email us with questions .

A few things to note we DO include oiling out among Best Practices but feel it should be used judiciously and only when and where needed, rather than applied as an overall layer. By using it only where you plan to repaint that day, any oil left on the surface after wiping away the excess would simply merge and be part of the whole and not represent a truly separate, intervening layer. On the other hand, applying oil over areas where it is left to dry on its own runs the risk of additional yellowing and darkening in the future, and if ever needing to paint over those areas later on, there could be potential wetting and adhesion issues. Granted a lot of this is an issue of degree and we are choosing to ere on the side of caution, especially as we know conservators who have been confronted with older paintings where the broad use of oiling out caused issues with no good solution. As for glazing, this is great question. Certainly using all over,glazes with very little color will run the same risks of yellowing and make subsequent painting in those areas difficult. A lot of the yellowing of glazes is not noticed in many older paintings because they were frequently used to deepen and develop the darks, or to provide warmth to an area that then simply grew warmer still the resulting patina even being, at times, prized, like the admiration we have for old furniture. So its complicated.

If possible, repaint a sunken-in area with the same or similar color but this time add a small amount of a bodied oil, such as Stand Oil, which should prevent any further sinking in and, as a result, should dry with a soft but even sheen.

Image 11: Raw Umber and Phthalo Green on Two Coats of WIlliamsburg Titanium Oil Ground(Click image for higher resolution)

Unfortunately I am in Peru until June 6th so cannot go into much depth at the moment. Long and short oiling out over areas you will not paint on shortly afterwards is not supported by conservation research as they have had many old paintings that are irreparably yellowed or have other issues as a result. The best thing to do is to adjust your ground, painting techniques, and possibly the type of medium used to limit the amount of sinking you are having.

My question to you is, how do I fix this problem and bring back the richness of the dark brown? If I were to repaint, would I need to paint a thicker layer? Or would I need to change the medium to maybe stand oil + Gamsol? If I were to use varnish instead, would I need to apply retouch varnish first to the sunken in passages before I apply a final varnish to the whole painting? How long would I need to wait between applications of retouch varnish and final varnish? Could you recommend a good retouch varnish and final varnish?

The most common chorus as to the causes of sunken-in patches of paint tends to focus on two areas overly absorbent grounds and paints thinned with too much solvent. And of course these are two faces of the same coin, as both imply that the paint has become underbound to some extent: in one instance, by the oil being pulled down into a thirsty, matte surface, while in the other being spread out too thinly and readily soaking into the underlying layer. We wanted to put both of these causes to the test, so painted various swatches over an assortment of grounds, including GOLDEN Gesso, Acrylic Ground for Pastels, Absorbent Ground, and Williamsburg Titanium Oil Ground and Lead Oil Ground. For paints we chose Raw Umber, a color commonly associated with sinking-in, and Phthalo Green, which dries to a reliably glossy film like most synthetic organics.These were applied in various ways: thickly brushed out, blended with odorless mineral spirits to the consistency of cream, rubbed out with a cloth or cotton swab, and finally, mixed with a fast drying alkyd or Stand Oil as a glaze (Image 2).

DO NOT USE.More than any other practice, this is likely the worst option as it introduces a permanent layer of oil that will only darken and yellow with time and with few treatment options available to reverse this condition. Also, should you need to paint on it further, the dried layer of oil or medium could cause issues with adhesion, beading, and potential problems with cracking in the future.

Oiling Out and the Cause of Dead Spots in Oil Paintings

What do you think of oiling out sunken areas with safflower (with or without a little alkyd in it), even if Im not going to repaint those areas, and then varnishing later when the time is right?

Its important to note that the connection between absorbent grounds and sinking-in stretches well back into the historical record, with documents recording artists bemoaning, complaining and finding fixes for grounds they felt were too absorbent. At the same time, a seemingly equal number pursued them with fervor, especially during Impressionism and other periods when a matte surface was actually prized and thought to give a more direct, brighter, and less yellowing appearance. So this is not a new issue that can be easily hung at the door of modern formulations or materials, but rather a common one known to occur with even the most traditional materials of the highest quality.

Hi Suzanne You are so welcome! And thank you for taking the time to let us know that you enjoyed the article. Stand Oil is indeed useful as it yellows much less than regular linseed oil while also helping the paint to level, besides also helping with dead spots. Just keep in mind it dries slower than most oils, but then oil painting is nothing if not a constant reminder that patience is a virtue. As always, if we can do anything else, just let us know!

Thank you very much for this work, which has much more depth than anything Ive read on the subject before. I have a question about oiling out to remedy sinking. I understand why this is a bad idea with linseed or an oil that is known to yellow, but what about oiling out with safflower or another type of oil that isnt going to yellow? Or, is the long term problem caused by the fact that a layer of oil (regardless of type) will attract dirt which will cause it to yellow, and it wont be removable as a varnish would be? Im really trying to find a combination that will work in the short and long term. I dont want sunken areas if a painting sells quickly or is a commission that the client doesnt want to wait 6-12 months for, but I also dont want to jeopardize the future of the work. I have been using a thin layer of alkyd to oil out, but am rethinking that thanks to this information.

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Lastly, to avoid this problem in the future, you might want to check to see if your ground is too absorbent. Not knowing what you are using it is hard for us to say if you need to change. If using an acrylic ground, or a preprimed canvas, you might look to first apply an oil ground to the surface which can help by often being less absorbent overall. Then tweaking the medium you are using, by adding or swapping in some Stand Oil can also help. In truth p

Reading your article I did learn that I will be using retouch varnish just to be on the safer side. Thanks.

As for Gamblin, we cannot speak to their positions and at the end of the day we simply have a difference of opinion or philosophy on some issues. Overall we are known to err heavily on the side of caution and, as best we can, to follow what we consider best practice in light of current conservation research. That said, conservation is a large and evolving field and finding consensus, even there, is a rare thing.

Image 1: Example of sunken-in areas in an oil painting.(Click image for higher resolution)

Painting with dead spots before and after oiling out(Click image for higher resolution)

Q: I have a question about oiling out to remedy sinking. I understand why this is a bad idea with linseed or an oil that is known to yellow, but what about oiling out with safflower or another type of oil that isnt going to yellow?

Image 7: Raw Umber and Phthalo Green on Four Coats of GOLDEN Acrylic Gesso(Click image for higher resolution)

Thanks again for your help and advice.

You are adding too much solvent to your paint. Try to avoid using too much solvent or even any solvent at all.

I thought final varnishing doesnt do much to remedy sunken passages? Or if it doesnt its only temporary?

Thanks for this. Since I have never gone to school for art, I wasnt sure what the stand oil was even for!

They even say it is part of having a more stable painting in that article. And when people glaze (say with liquin or galkyd) wouldnt that then not be ideal for a painting top surface before varnishing? Clearly those oils or safflower oil like you mentioned above will yellow over time even if it has color in a glaze?

The second set of examples (Image 4) are simply two thicker piles of paint that were then scraped with a palette knife to create a thin film on a lacquered, non-absorbent drawdown card. In both cases the glossiness evident in the body of paint is lost in the thin scrape-out, where the thinner the paint the more matte the appearance. In fact, at its thinnest, the paint takes on an almost powdery appearance.

Thanks Sarah!  I cannot paint without oiling out.  If I skip this crucial step, then Im astonished at the nasty surprises that suddenly appear upon varnishing.  These surprises had sunk in and were not visible during the painting process.  I find that oiling out is like a dress rehearsal for the final varnishing.  It reveals the unseen and indicates what the final painting will look like.  But there is always the issue of time.  I cant use slow-drying oils and still complete a painting in a reasonable time frame. Finding a fast-drying oiling out medium is challenging. Some painters abuse fast-drying alkyd resins by oiling out with them.  I know of painters who begin a days work by applying a layer of Liquin over their work.  Few of them realize that this is precarious.  It would be great if manufacturers could produce a fast-drying Oiling Out Medium.  Sadly, this isnt an option. Thickened Linseed Oil is too viscous for me, even when diluted with a solvent. Im tempted to try Drying Linseed Oil as an oiling out medium, perhaps diluted with a solvent. How does that sound to you Sarah?

I know that is not an ideal answer for your needs but is really the best practice we can recommend.

Image 4: Different sheens of paint due to thicknesses on non-absorbent drawdown cards. Ultramarine Blue French and Ultramarine Pink.(Click image for higher resolution)

As for how to correct things, if repainting is an option then that would be great and yes, using a medium with Stand Oil as mentioned above can help. As for painting it more thickly, you might not need to. What we would recommend is first oiling out the areas where you will repaint using a blend of Stand Oil thinned with some Gamsol and letting that sit for a bit before wiping off any excess. This will help quench the thirst of the sunken-in areas, so to speak, and should allow the new layer to dry more evenly. If not wanting to repaint, then you could correct this when you decide to varnish but know that we recommend waiting 6-12 months after a painting is finished before applying a final varnish, so this might not be an option if you have just recently completed things. For future reference we make a series of varnishes that are compatible with oil paints, called MSA Varnish, that would be worth looking into:

A: While Safflower will definitely yellow less, it will STILL yellow some over time. So one is not completely rid of that issue. Plus Safflower oil makes a less durable and more brittle film, so having it as a permanent coating on top of the paint, or in between layers, is not necessarily ideal. That said, if you are oiling out IN ORDER to resume painting on top, and have been using Safflower oil in your mediums as paints, then using Safflower oil as a way to remain consistent would have some validity.

Also, retouch varnish often seems to remain a little bit tacky, and that makes me distrust it, so I dont think thats a good solution anyway.

Hi Matte Thanks for the comment and glad to hear that the article was helpful, even though it seems to have raised as many issues for you as it resolved.

In the last example (Image 5) we show Cobalt Blue Deep and Raw Umber cast over Williamsburg Lead Oil Ground on polyester film. These are both cast at 6 mil thick, about the same as two sheets of paper, and clearly show the degrees of gloss you would expect for a well bound film. The thin, very matte strips to the top and sides are areas where the paint was scraped very thinly by the drawdown bar during application. The bands to the left are on the polyester film, while the ones on top are on the Oil Ground. This is important as it shows that the dead matte appearance is independent of any difference in absorbency between the Oil Ground and polyester film. Again, the only explanation is that the paints, when applied very thinly, can have the same appearance as a sunken-in area usually attributed to solvents or an overly absorbent surface.

Hope this helps and if we can do anything else just ask!

Lastly, how do I avoid this sinking in for future dark passages? Is the solution painting a thicker layer with less medium? Or continue to paint in thin layers but with a medium that includes stand oil?

Despite the name, this isnotrecommended as a way to remedy sunken-in areas of color during the course of a painting. Doing so complicates the structure of the piece by introducing a very different material in between paint layers, not to mention that retouch varnishes are almost always removable and therefore poses a problem for future conservation and cleaning as they could be reactivated. That said, if you have used these, simply make sure to make note of it on the back of your painting.

Sarah Sands, Senior Technical Specialist, MFA Yale University. Prior to Golden: Instructor, NY Academy of Art; Associate Professor of Painting, Indiana University; Business Manager/Technical Specialist, Williamsburg Oils

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Thanks so much in advance for your help!

Both performed well, with minor differences mostly related to their sheen. The glossier Titanium Oil Ground allowed for glossier paints overall, although rubbed-out and solvent-thinned applications of Raw Umber still appeared blotchy and dry when no mediums were added. Phthalo Green, on the other hand, appeared glossy on both, even in the rubbed out areas. (Images 10 & 11)

While only including two in this testing, they performed as expected, with Phthalo Green creating a glossier film in all instances, even when thinned with solvent to a very fluid consistency and applied on an extremely absorbent ground. As Phthalo Green has less oil by volume than Raw Umber, this is clearly a function of pigment particle size more than anything else.

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In the first one (Image 3) we applied Raw Umber and Phthalo Green in three different thicknesses onto a non-absorbent polyester film. Sheen is notoriously difficult to capture in a photo, but if you follow the reflections across the curved surface you can see changing degrees of gloss. For Phthalo Green, the gloss actually increases the thinner the paint is applied. Raw Umber, on the other hand, grows increasingly matte and in a very thin film, has a nearly dead flat appearance. Since none of this can be caused by absorbency, and Phthalo Green has evenlessoil by volume than Raw Umber, the only possible explanation is that the particle sizes of the different pigments have a large impact on the final sheen of the paint, especially when applied very thinly.

Hi Donna We are so glad you enjoyed the article and found it useful! Dead spots can definitely try ones patience when waiting for a painting to dry enough to varnish, but ultimately that really is the best way to even out the sheen. As always, if there is anything else we can ever do, just let us know. Until then, best of luck with all your painting!

Thanks for the comment and questions. Fist definitely know that the blend of colors you used included many that have long reputations for drying unevenly, so you are not alone! And definitely if you found that applying a thin layer with the first medium resulted in dead areas, then switching to one using a bodied oil, such as Stand, could be helpful since it will not soak into the underlying layers as readily.

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