Why does oil based paint turn yellow

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You have no items in your cart. What follows does not attempt to solve or lend support to a particular theory. Rather it simply shares our empirical findings from a multitude of tests that have been ongoing since , when we first acquired Williamsburg Handmade Oils.

In terms of age, the examples run from just under 9 years old up to ones that are currently 2. Collectively all of these would still be considered very young films, still in the first stages of the processes and changes that will continue for centuries. We tested 14 oils in all, representing a wide range of the common ones available from different oil and paint companies, as well as more unusual options. The oils were tested by themselves, as well as being made into a series of Titanium White paints.

In that part of the testing, we followed two different approaches. In one, we created a basic, representative formula for Titanium White and simply changed the oil being used, making minor adjustments when needed to keep the thickness of the paint the same. We created a second series where the same oil and pigment were blended with different components, as a way to gauge the impact of each ingredient, moving from a simple combination of just pigment and oil all the way to a fuller and more complex formulation.

This area of our research held few surprises at the broadest level: poppy yellowed least, followed closely by safflower and walnut, and behind them a large grouping of linseed oils showing only the slightest variations among themselves. And perhaps just that sense of sameness was the most noteworthy and compelling feature; like most, we went into this expecting to see a clearer difference between alkali-refined, cold-pressed, and the traditionally water-washed versions.

In fact, that was the initial hypothesis we wanted to document when we started these trials. We tested oils in several ways and at various thicknesses. In one test we applied them to glass slides that were frosted, as well as ones having a small concave depression or well where we placed either one or three drops of oil. All samples were then kept under ambient conditions, exposed to alternating cycles of 12 hrs.

Nearly every sample was prepared in triplicate and no variance was noted in the results. As one can see, the results on the filter paper are tightly grouped. While the poppy oil is indeed lighter, followed by walnut and safflower, all the other examples tended to be indistinguishable Image 1. Separately, the glass slides showed similar results, although the larger volumes of oil did seem to generate slightly more variance in color, while oils like poppy and walnut displayed far less surface wrinkling, likely due to slower drying times delaying the formation of surface skin.

Very thin films on frosted slides, on the other hand, appeared nearly identical across all samples and displayed such a small degree of color they appear essentially clear Image 2. This difference between thick and thin films is something we also noticed in other testing, where 3 mil films of oil about the thickness of a sheet of paper were drawn down on top of acrylic gesso. In the example we show Image 3 of an alkali-refined linseed oil, cast in and later kept pinned to a wall in an office, the very thin area has just the slightest tint of color, while the oil that spread and gathered off to the right side, culminating in a 9 mil area towards the top, took on an increasingly amber tone.

Whether the drops of oil on the slides will develop along similar lines over the next years remains to be seen. This dichotomy between thin and thicker films of oil makes it problematic to hang too much weight on examples of yellowing where the oil has pooled and formed a solid mass, like one can sometimes find around the neck of an old tube of paint.

While these can be dramatic and raise alarm, it is also true that it is never advisable to use oil in this way. Even in glazing, where mediums start to play a dominant role, the applications should always be kept as thin and lean as possible to limit any yellowing.

This also holds true when working with thickened oil or alkyd-based impasto and extender mediums, where it can be tempting to create thick translucent textures that can unfortunately yellow dramatically and irreversibly over time. If the oils themselves felt close in appearance, things became even tighter once they were made into batches of Titanium White. After 2. In fact, the differences are so small that the inherent limitations of screens and printed pages have made capturing them reliably in a photo next to impossible Image 4.

In the end, the hoped for evidence that this or that oil causes the whites to yellow markedly more than another simply never materialized. Rather the dictum that eventually, ultimately, most oils converge toward a similar appearance would seem the better fit for what we eventually found; at least given the test conditions and time frame. Further aging might still crown a clear winner, and other factors besides the oil alone might prove to have the more lasting and decisive impact.

You can see this convergence taking place over time by using a spectrophotometer to measure the initial yellowness of the paints fresh from the tube and following them as they dry and age.

In the graph Figure 1 you can see that the paints have their greatest differences right at the start. After just one day most of the paints actually became whiter, and by the end of the week, when they had all dried to the touch, their differences began to flatten out.

From there to their current state at 2. The importance here is not simply to highlight the difference between the two mediums, but because the brightness inherent in white acrylic paints and gessos have set a standard that we often judge things against.

However this can also end up magnifying our sense of just how much difference you might actually notice if you saw these swatches, especially if separated by some space or in the context of different paintings.

If anything stands out as remarkable, it is perhaps the overall sameness that we noted when looking at just the oils — the different brands of alkali-refined, bleached, or cold pressed linseed, as well as traditionally cleaned and water washed ones, in the end all simply crowded close together.

Does this mean that all the passions spent advocating for one or another of these variations are simply much ado about nothing? That all the claims of decreased yellowing might not matter all that much in the end? Or this could simply be the usual bunching-up that one sees at the start of any long distance race.

We are barely out of the blocks after all, and patience is called for. Still, these results defy most expectations and stand in contrast to other panels of various whites that even we have created.

That said, these are still the first large set of controlled examples that we know of, compromised of some 90 swatches all made to a similar formula and kept under the same conditions, where only the type of oil changes. We will ultimately go wherever the evidence leads, while still looking to confirm these findings in future rounds.

This is an area that has remained largely unstudied in any systematic way. Research on oils in and of themselves, as well as treated by various methods, are easier to find, along with ones that blend oils with single pigments and perhaps some drier. Absent in all those are studies that take a look at the impact of all the various components that make up most modern oil paints. Our own work in this area dates back to , when we acquired Williamsburg Handmade Oil Colors, and some results start to come in that are interesting to look at.

In the assembled examples Image 5 , the paint made with just Titanium White and alkali-refined linseed oil yellowed the most, belying the common belief that simple blends of pigment and oil are always the best. The next two variations, which include the addition of barium sulfate or precipitated calcium carbonate, become increasingly less yellow while also showing a corresponding drop in oil exuding to the surface or out the sides.

This would also explain why the paints become significantly whiter, especially in the thick application, once beeswax was added in as a stabilizer, or why the addition of drier on top of that would help even further. The beneficial effects of drier in this regard is noteworthy as far too often it is claimed that their use leads to more yellowing, not less.

This is the opposite of everything we have observed. However, these tests do not include the full range of available drier combinations, their use in distinctly different paint formulas, under different environmental conditions, or at levels that would be considered excessive. While the pressing-out of oil is dramatically captured in the 60 mil disks, it is worth speculating that a similar but much smaller-scale process could be happening in the thinner swatches as well — namely that oil is rising to the surface at a microscopic level, and forming a thin, yellowed film around the topmost layer of pigment.

This phenomenon around the formation of a skin of medium on top of the paint has been noted by current researchers of modern oil paints, although the exact cause has not been established Izzo, F.

We also know that this type of phenomenon is one of the main reasons that Zinc Oxide was used so frequently in conjunction with titanium dioxide. The combination of beeswax and drier used in these tests might be helping along similar lines, but without the downsides with zinc. Dark yellowing is a well-known phenomenon where oil-based paints stored in the dark will yellow significantly, although the yellowing is thought to be fully reversible by exposing the paints to light Levinson,H.

This is an area we have written about before Sands, S. Having a selection of swatches kept in dark storage for around 6 years, and examples of the same formulas kept in ambient, indoor light for 3 months and another set for 2.

Differences in yellowing could be found in all three stages. Of the swatches kept in the dark, the one made with cold-pressed linseed did the worst, followed closely by alkali-refined, then safflower and the others. The paint made with just pigment and stand oil did the best in this category, although it should be noted the paint itself was unpleasant to work with because the oil was so viscous. The fully formulated paint did far better than the same pigment mixed with just ARLO or CPLO, and in the end nearly equaled the paints made with safflower or that included zinc in the mix.

It is also critical to note just how long it took these paints to recover from long-term dark storage when exposed to just typical indoor light levels. After 3 months the recovery was still only partial when compared to similar examples in the same room for 2. Thus the time needed to fully reverse the effect of dark yellowing can take far longer than many people might realize.

Needing this type of long recovery period has also been noted in more recent conservation research Townsend, D. If the yellowing of the oil based enamel is due to poor ventilation and exposure to ammonia, then the enamel should be allowed to cure sufficiently, then lightly sanded and repainted with a non-yellow water based acrylic enamel product like Haymes Ultratrim Acrylic Enamel High Gloss or Semi Gloss. If an area such as a door or skirting is going to be painted with a white or pale colour and colour and yellowing is an issue, then water based acrylic enamel technology like Haymes Ultratrim Acrylic Enamel High Gloss and Semi Gloss can be used as an alternative to the oil based products.

These are acrylic paints will not yellow like the oil based enamel products. Haymes Paint has an ongoing development process in the area of trim products to ensure products with excellent film toughness and low yellowing. The information provided is correct at the time of preparation; however it is the responsibility of those using this information to check that it is current prior to specifying, recommending or using products contained in this information.

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Oil based gloss does discolour and go yellow over time as the oil content comes to the surface causing the discolouration. In future do not use oil based paints. Use water based gloss, eggshell and satin instead.

To solve the yellowing, when the Polycrylic is just tacky almost dry spray a light mist of 1 part vinegar to 10 parts water and wipe off with a clean cloth.

The yellow will wipe off leaving the finish clear. The yellow will not return when the Polycrilic dries. Use a non yellowing polyurethane to prevent this. Spray the cabinets with the mixture, one cabinet at a time. Rinse the sponge, wring it out, and wipe the cabinet again to remove the cleanser.

Dry the cabinet with a soft towel or rag. Writer Lorna Hordos suggests removing a yellow tinge this way: Wash your cupboards with a fizzy mixture of 1 cup vinegar, 2 cups warm water and 1 tablespoon baking soda. Oil based is best in terms of durability BUT 1 you need to be careful pick a brand that won't yellow I recommend Sikkens and 2 it is much fumier. Rinse the car and allow it to dry completely.

Pour liquid rubbing compound onto a cotton towel. Use a small amount and add more as needed. Apply a small amount of car polish to a clean cotton towel and polish each area that was rubbed with compound. Water based gloss can be cleaned from brushes without the use of solvents with a soap and water mixture, making it less harmful to health due to the absence of fumes to inhale.