It is most noticeable in situations where the natural lighting is poor, for example sliding cavity doors, inside door jambs, behind furniture or inside cupboards. It has been extensively researched and is known to be due to the presence of chromophores coloured chemicals that are formed during the paints drying process. These chromophores are sensitive to light and will be bleached out of the paint film if exposed to daylight. Some alkyd enamel paints discolour more than others depending on the type of vegetable oil blend eg.
Good ventilation, with the aid of fans, during application and during the drying period for all water-based paints will allow ammonia vapours if present to escape more quickly.
As an alternative to conventional water-based paints, low VOC water-based paints that usually do not contain ammonia can be employed. In order to prevent this problem, it is recommended to avoid applying white or light coloured enamel or alkyd paints in presence of water-based paints at the same time, because it can adversely and permanently affect the colour of the alkyd enamel.
Light, and lack of light, can affect how well paint color is preserved and how quickly it yellows. In the case of yellowing due to lack of light, chromophores are to blame. Chromophores are produced as oil-based paint dries, and are a natural part of the process. Chromophores are broken down by exposure to light. If your white painted wall is exposed to light most of the time, it is likely to stay beautiful and white. The parts hidden behind the furniture are likely to suffer from the yellow tinge of chromophores.
Moisture is another common environmental cause of yellowing paint. Smoking in the home and cooking can also cause moisture to be released into the air and settle on the paintwork, leaving yellow stains. Moisture is a common cause of white paint turning yellow on wood and white painted cabinets turning yellow, as cabinets are often located in places that receive more moisture.
For example, kitchens and bathrooms are among areas most exposed. If paint yellows due to lack of light, it is often easily resolved.
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. For testing of the 14 different whites, each of the paints was made using a basic formula of oil, titanium dioxide, synthetic precipitated calcium carbonate, barium sulfate, beeswax and a low level of cobalt-manganese drier. These were then cast directly onto polyester film that was either uncoated or had a layer of acrylic gesso applied as a ground.
We used polyester because it is non-reactive and stable, while the addition of acrylic gesso simulates some of the absorbency one gets when painting on a typically primed canvas. The samples were then stored under ambient conditions with light coming from color corrected fluorescent bulbs on a 12 hr. They have not undergone any prolonged dark storage.
In any test, what is left out can be as important as what is included. We did not control for humidity or temperature, two environmental factors commonly linked to increased yellowing. No mediums were included. The driers were limited to either a low or medium level of a single cobalt-manganese combo, and a host of other potential modifiers and additives were left out, such as hydrogenated castor wax, magnesium carbonate, and aluminum stearate.
The range of substrates and grounds were also very limited, and we mainly cast the paints onto polyester film that was either coated with GOLDEN Acrylic Gesso or left plain, although one set of examples were applied to acrylic gessoed canvas.
In terms of pigment, we tested only one type of rutile titanium dioxide, supplemented by zinc oxide in two examples, but did not test basic lead carbonate, lithopone, or zinc oxide by itself. Finally, we did not include other brands of paint for comparison since we had no way of knowing their exact ingredients, and therefore no way to know what might be responsible for any results in either direction.
At the moment, none of this testing will definitively resolve which oil or formula of Titanium White will yellow the least. But at least it starts to give us a controlled set of paints kept under controlled conditions that can form one basis of the discussion. More rounds of testing using fresh drawdowns of yet more variations, are in the works and as those results come in, and these original swatches continue to age, we will certainly publish and share those findings.
This is work and research that will literally go on for decades, long past the lives of most of us in the Lab. The hope is that in the future, when all those questions about oils and yellowing continue to be asked, that the answers will have a firmer footing.
Burnstock, A, van den Berg, K. Subscribe to the newsletter today! Thanks Richard — as always I truly value your appreciation for the work and research we do. Thanks Jean! Definitely some curious results that ran counter to some of our own expectations. Will be interesting to see where this ends up at the 5 and year mark.
Hi Avery. We did not purposively ignore Lead White as much as simply needing to start somewhere and Titanium White is unarguably the most broadly used white for paints and grounds.
Plus it has some unique issues, like its tendency to push oil to the surface. Our hope is to include lead white in future rounds, as well as lithopone PW 5 , and to explore more fully the impact of functional solids as well as stabilizers like aluminum stearate that are used broadly by artist paint manufacturers, although we have chosen to use small amounts of beeswax ourselves. So a lot to look forward to!
The walnut oil paint has far less resin like qualities compared with the hand refined linseed which is something I miss. Hi Darren — Thanks for the comment and sharing your experience. In some future iteration, we hope to include more walnut oil, and especially a water-washed one, just as another variation to look at.
It is, along with linseed, one of those classic oils stretching back to the Renaissance, but is often talked about has having a thinner, slippery-like feel which some love, but others will miss — as you seem to do — the more bodied feel of linseed oil.
In any case, hand-refining oils is always a great way to learn about them and gain some insight into the past. And if we can ever help further, just ask! This is a very thorough examination of the darkening of oils. I am very appreciative of Golden for providing artists with these results to think about.
Interesting figure 5 how bees wax sample 4 reduces surface oil to inhibit yellowing, and so does low cobalt drier sample 7 but not high cobalt drier sample 6. I was under the misunderstanding bees wax increases yellowing. This is an area palette knife painters could consider, as knife work has had the reputation to increase yellowing by drawing oil to the surface. What were the concentrations of cobalt drier and bees wax used?
I am interested to see where this study heads to in about 10 years time, especially with stand oil and bees wax. Thank you once again. Thanks for the compliments about the thoroughness of our testing and the sharing of the results.
Feedback like yours means a lot to us. Also, know that the spirit of open-ended inquiry and a desire to make as much information available as we can are cornerstones of our culture here. In terms of your questions, you are correct that beeswax has that reputation but we think it is tied more to the fact that, at higher percentages, it increases transparency enough that the inherent yellowing of the oil is not masked.
You can determine if the cleaning product contains ammonia by reading the label section of the cleaning product that lists the ingredients. If the yellowing of the oil based enamel was due to the absence of natural light, then the yellowing can be reversed over time by exposing the paint work to light.
This reversal is not instantaneous and depending on the light level in the room could take some time. 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.
Because use conditions and applicable laws may differ from one location to another and may change with time, those using this information are responsible for determining whether products and the information in this document are appropriate for their use and for ensuring that workplace and disposal practices are in compliance with applicable laws and other government enactments. Haymes Paint assumes no obligation or liability for the information in this document.
No express warranties are given except for any applicable written warranties specifically provided by Haymes Paint.
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