Every once in a while we receive inquiries from artists who use our products with Masterson Sta-Wet Palettes, a sealable palette system that keeps acrylic paints workable for days or even weeks by utilizing a wet sponge and permeable palette paper. Some of these artists shared that certain GOLDEN Artist Acrylic colors were changing consistency when used in a Sta-Wet Palette for an extended period of time. While Masterson does not recommend prolonged storage beyond a few weeks, some artists still practice this. After conducting some tests, we have determined that this issue might be related to surfactants. We have also found a simple solution that can help.
What are Surfactants?
Surfactants (surface-active agents) are basically soaps, which perform a variety of functions within an acrylic paint system. For example, they aid in pigment wetting, the feel when painting, and how paint lays down on a surface. In a sense, surfactants are crucial to the overall stability and performance of acrylic paints.
Surfactants are also quite mobile depending upon their environment. In a damp setting, like a Sta-Wet Palette, there are areas of high surfactant concentration (paint) and low (sponge). Due to this disparity, there can be diffusion across the gradient until there is a more even distribution of surfactants. Essentially, we suspect surfactants may be migrating from the GOLDEN Artist Acrylic paints into the water, which is disrupting their stability. Since pigments are unique and require different formulations, this may affect individual colors or even brands differently. No two paints are exactly alike.
The “Solution”
In our testing, we found that using a solution of distilled water and GOLDEN Wetting Aid to saturate the Sta-Wet Palette sponge helped maintain the feel of GOLDEN Acrylics for weeks or longer. That being said, if storing beyond the manufacturer’s recommendation, consider it more experimental. Routinely refreshing the palette after a few weeks would be best practice.
Recipe
We suggest using a ratio of 32 parts distilled water to 1 part Wetting Aid as it is a concentrated surfactant. To make things easier when measuring, we created a mixture of 8 ounces of water with 1/4 ounce of Wetting Aid during our testing. We followed the manufacturer recommendations for preparing the palette and used this mixture to moisten the sponge and keep it hydrated as needed. In our testing, this mixture proved to be the most effective in maintaining the stability of GOLDEN Acrylics in a Sta-Wet Palette.
It’s important to note that we conducted the tests in a controlled environment. We didn’t dip wet brushes into the paints while they were in storage as it could have affected the results. If an artist uses tap water to thin their paints, a wet brush may introduce microbes. However, we found that adding ¼ ounce of household ammonia to the distilled water and wetting aid solution was equally effective in maintaining paint consistency. Small amounts of household ammonia can help raise the pH of the water. This helps prevent mildew or unpleasant odors that may develop over time due to microbial growth. You can use household ammonia without affecting the paints or palette paper.
Conclusion
If you have experienced changes in consistency of your GOLDEN Acrylics used in a Sta-Wet Palette, we hope this helps! If in your use of the Sta-Wet Palette you haven’t encountered this, no need to change what you are doing. As always, if you have any questions just let us know at [email protected].
super interesting
it’s actually quite a problem for miniature painters
(not the classic one, but the resin/plastic small scale model
(such as tabletop warhammer 40k stuff
basically every miniature painter use certain wet palette
though the paint do keep wet on that wet palette
but paint’s feel may change
(absorb too much water and get separated easily
and not so much information/discussion on that
Hello Nourkias. If the palette is too wet, it will reduce the viscosity of the paints. As the paints absorb some of the water, like you say, they will gradually loosen up the paint over time depending upon amount of water and how long paints sit on a wet palette. There isn’t a whole lot that can be done to mitigate that besides controlling the amount of water used. We hope this article was helpful and let us know if you have more questions! [email protected]
Scott
I’ve been using this recipe and been telling people about it since you told me about it in an email.
So many thought it was too tedious and too much effort until they tried it and found it just was so much better.
Soflats and fluids still have some issues but most of that comes down to the quality of the parchment people use from what I’m finding as that thick paper it comes with is super tricky to use.
I sometimes leave the pallet closed for well past the manufacturer recommended length due to getting incredibly busy but its been about a year and still no mold on the sponge.
We are glad this seemed to help when you tested it out. It can require some additional preparation, but it seems to really help! We did out testing on the paper that was supplied with the Sta-Wet palette and had good enough results, but we weren’t painting with it per se. So there may be additional needs based on mixing and working the palette paper more. A year is a very long time and certainly not the norm, but interesting results. We were able to get a few months, but again we had best results within a few weeks.
Scott
Thanks for first-hand user insights.
What papers are being used instead of Sta-Wet’s own palette paper? You mention “parchment” and I’d like to know if you mean regular parchment paper for baking? If so, are you aware of which brand(s) work well?
Scott,
I agree with the previous comment that the real issue is how much water to add to the sponge. That would be useful information to supplement your article. I add too much and the paints thin out, too little and they dry up. The instructions from Masterson don’t offer much help as you are just squeezing out some of the water. Is there a better more precise technique?
Hello Jay,
We don’t have a scientific way to managing the water. So much depends upon the type of paint being used and the length of storage within this system. You could formalize it by using weight if you wanted to be precise. After you finish a session you could weight the palette and replenish what is lost to evaporation through use. Simply re-weigh the palette again periodically or prior to using it again and using that amount of water to replenish. You could also use a spray misting bottle and lightly spray the colors with this distilled water mixture with wetting aid or with distilled water generally. We found this was helpful in controlling the amount of water we used, but it can also loosen up the paint a bit. Not sure this solves it, but it is a more formal way to approach how much water you are using. Let us know if you have more questions! [email protected]
Best,
Scott
Helpful and interesting. I pretty quickly did away with the sponge and palette paper and switched to a glass palette from Posh that fit inside the Masterson Sta-Wet box. Underneath the glass palette, I sprinkled some baking soda. Along two sides of the glass, I placed folded paper towels soaked with tap water and a little hydrogen peroxide. The piles of paint went on top of the paper towels and mixes were done on the glass. This setup kept the paint fresh and wet for weeks, but if the mixes were thin, they would dry and I would have to scrape them up. I like this setup better than the sponge and paper. The sponge got sour pretty quickly and I didn’t like the bounce or give when mixing.
Thanks for sharing your experience Allen. We have heard from some artists using the paper towels as well, but not the glass. It makes sense and Sta-Wet recommends the use of Hydrogen Peroxide to help stave off some microbial growth as well. There is certainly some experimentation that can happen to find something that works best for each artists needs! Thanks again for sharing!
Scott
I find that 1 Tablespoon of bleach and 1 tablespoon of borax per gallon of distilled water keeps the nasty out of my masterson box for weeks at a time.
Hello MaryAnne,
Bleach would not be recommended as it can react with ammonia to form some nasty compounds. Acrylic paints contain ammonia, so using bleach can be dangerous and should be avoided.
Borax is a salt – so not as much of a concern other than untested with our system – as a salt it could affect some surfactants and if absorbed into a paint increase sensitivities but fairly effective as a anti-microbial it makes pH elevated so similar to the Sodium Carbonate solution in function.
We hope this helps and let us know if you have questions at [email protected]
Scott
Q1. What is the point of the baking soda under the glass palette?
Q2. Regarding the folded paper towels along two sides of the glass palette:
Are the paper towels located *on the surface* of the glass near the edges of that glass surface?
Or is the glass palette smaller than the Sta-Wet box, so the paper towels are located *next to* the glass palette?
Thank you for publicizing this investigation Scott.
I’ve been using the sta-wet palettes on and off- mostly for mixture storage in between sessions, and once I discovered adding household ammonia to my water sprayers, my issues with mold growth and mixtures going gelatinous have disappeared.
I even give my jar colors a quick spritz occasionally too, since the tap water I use copiously seems to be highly microbial..
PS and in earlier experiments, I found that hydrogen peroxide did not really do the trick.
Much to my chagrin, I tried the ammonia-laced water as a mold preventative for some watercolors that I have stored in small jars, but that was ruinous to the gum Arabic, ouch. Fortunately I only wrecked a couple of colors before realizing what was hoing on..
It is good to know about your experience with Gum Arabic watercolors. Acrylics have some ammonia within them, so the ammonia doesn’t affect them in this way. Glad you did some testing and thanks for sharing your experience!
Scott
Very excited to see this article, as I use both the golden and the sta-wet exclusively. I notice that my sponges deteriorate very quickly, holes get eroded here and there. Any idea why this happens?
Hello Paul,
We sent out an email to you separately. For those with similar experiences, microbial growth, if it develops, can eat the cellulose sponge material. We are not sure what the sponge is made from as is proprietary, but this is one thought. So keeping your eyes on the palette can be helpful and if you run into this you could always try using a small amount of Household Ammonia in the distilled water to raise the pH a bit, which helps. No tap water is exactly alike, so there can be varying results depending upon your water source. Hope this helps!
Scott
Paul, some paints (especially phthalos) seem to be more caustic than others. Try this: wring out a new wet sponge, lay it in the palette, and spray the sponge lightly with a 50-50% mixture of household ammonia and water. Position a single layer of paper towels over the sponge, and then lay a piece of prepared Sta-wet paper on top of the paper towels. By adding a paper towel layer, I find that the paint does not deteriorate the sponges, and they last much longer. The ammonia-water spray will keep any mold from forming–mold, left for very long, can eat through both the paper and the sponge.
Thanks for the detailed response to Paul, Yvonne! Household ammonia is strong, and adding ammonia should be minimal. The concept is to raise the pH level into the low to mid 8.0 range so that you don’t overwhelm yourself from the fumes but stave off the mold which needs near neutral pH in order to grow. – Mike
Thank you for this article, Scott. Golden ‘Just Paint’ articles frequently convey information directly related to my own interests and methods.
In the course of your experiments did you see any evidence suggesting that the sponge will be damaged by either the Golden Wetting Aid or the Amonia?
I’m wondering if the Wetting Aid stiffened the sponge, and whether the Amonia might cause the sponge to disintegrate.
Our pleasure Tom. In our testing with Sta-Wet Palettes we didn’t see any issue in the time frame we tested at for the article, which was ~3weeks to a month. The paints were happy and the sponge looked good. Wetting Aid is essentially a surfactant or soap, so this didn’t affect the feel or stiffness of the sponge that we could observe. We did see some stiffness in areas that were low in water though as the sponge began to dry a bit. We saw great paint and sponge performance at ~3weeks time, beyond this is more experimental. Thanks Tom!
Scott
Thanks, Scott! I used Master’s palettes quite a bit, but got frustrated with how often the paints would become mildewed or smelly. I’m going to try your distilled water/wetting agent method and hopefully it’ll extend the life of my palette.
We hope this helps, distilled water with a little household ammonia has been helpful in our testing!
Scott
Another thing to help with preventing mold is to put a penny underneath the sponge. I hate the a ammonia and peroxide smell and this works way past manufacturers suggested time!
Thanks for sharing your experience Janet, that is interesting as well, we will have to try it out!
Scott
This has been one of the most interesting emails I’ve received. I’ve owned this palette for decades but have been away from painting almost as long. Glad I didn’t throw it out!!
It’s great to know that you can use ammonia or peroxide without damaging the paints. Very helpful.
Scott,
Is the distilled water and wetting agent used on the palette paper as well as the sponge? The manufacturer says to use hot water on the paper. How did you do that with the distilled water mix? Did you microwave it first?
Jay
Hello Jay,
We followed the manufacturers recommendations pretty closely. We boiled water and soaked the paper separately in a shallow tray. We did not microwave it. We tried two approaches to the sponge. We rinsed it with tap water real well in one test and the wrung it out carefully, before rehydrating it with the Distilled Water and Wetting Aid solution. We also tried letting the sponge fully dry after rinsing it and hydrating it with the solution once we prepared the paper. We didn’t see any real difference in results with either approach. To hydrate the sponge we used a 32oz container filled with distilled water and added one additional ounce of Wetting Aid. From there we got the sponge wet and wrung out excess if we over did it. Then placed the paper on top before adding paints. Periodically we would mist over the color and paper or add more to the sponge as needed. Controlling the amount of water in the sponge will help with the consistency you hope to maintain for your paints. There is certainly some trial and error needed to get that part just right. Keeping your eyes on the palette is helpful. Hope this helps!
Scott
Has to be pre-1982 pennies that have more copper. I put one under each corner and it seems to help.
I’ve been doing the same for quite a while now, and it really helped with the mold. I keep my paint in the palettes for months with good success. I also minimize the amount of water in the sponge. I usually have three palettes going at once, and use them for both Open and Heavy body. For Open I don’t use the sponge, and I put small balls of paper towels in the corners or slightly under the paper to keep some moisture in there. I spray lightly before closing.
Thanks Katherine! That is a good tip on the OPEN, we will have to try that. Since open is so good at holding onto moisture and is slow drying to begin with, having a small source not directly in contact with the paint may be enough to draw moisture to the paint. We haven’t tested this, but it sounds like one we should!
Scott
Great article! I work almost exclusively with Open Acrylics (GREAT product!) and am currently doing a summer course that required pre-mixing puddles of colours.
I do not use the Sta-wet palette for mixing. I mix on a separate surface, mostly an enamel pan. That is also where I put my paints when I am working on a painting. So the Sta-wet is just for storage.
It bit me in the you know what during the course, as all colour extended and ran into each other the day after putting the mixes in with a good inch of space in between. So I am very keen to try out the suggestions in this article to see if I get more life out of the paints.
They stayed workable for a good week, by the way, but some changed because they ran into each other.
So, for my own clarity I have some questions:
1. What is ‘a little ammonia’? How much is a little? And can we express the measurements in ml please. I get so confused by other measurements!
2. For the person who wrote in about putting balls of kitchen towel in the corners: were they soaked and the only source of water?
3. How do people work with the sponge when colour leaks onto it?
4. How to prevent, IF using a sponge, that it shrinks after wetting it?
5. Like others, I too have 3 different Sta-wet palettes, in different sizes. I love working with them. I did clip the small ‘tentacles’ in the two biggest ones, as they dipped into the paint puddles. Just wondering why they are there. In the biggest palette I am assuming it is to keep the lid off the paint, but still, having the ‘tentacles’ touch the paint does not help me.
6. Has anyone tried to create squares with painting tape to create mini compartments so the paint cannot run into another paint? This may be something to experiment with, or even equip the Sta-wets with: adding compartments but of course then having to find a solution for adding some kind of ‘sta-wet’ surface.
I will keep following this post. Thanks for all the information!
Cheers,
Nicky
Hello Nicky, We are not experts on the use of Stay-wet palettes, so most of your questions will be best answered by other artists. We can answer your question about what the article recommends in terms of ratios. The recommended ratio is 1/4 liquid ounce of Wetting Aid for 8 ounces of distilled water, and if household ammonia is also desired that also would be 1/4 ounce. According to Goggle, 1/4 liquid ounce is equivalent to 7.393382 milliliters. Eight liquid ounces would be equivalent to 236.588 milliliters. We hope this is helpful!
Great advice! I will have to try this. I use Redgrass wet pallets (both the older style and newer membrane) I will have to try this out on my old style pallet. I for sure notice some golden paints (depends on the colour) get watery the longer I leave them on (days). I also have a tendency to add too much water to the sponge lol. I bet this would work great for mini paints too, for all my fellow enthusiasts.
I have never had an issue with mold, but again different pallet brand.
We hope the information will be helpful. Happy painting!
Thanks for this article—it’s quite helpful. Is the 1/4 ounce of ammonia for 8 oz. of water or for 32 oz.?
We are glad you find the article helpful, Brie! The recommended ratio is 1/4 ounce of Wetting Aid for 8 ounces of distilled water. Should you wish to add household ammonia to this combination, the amount we suggest is also 1/4 ounce: eight ounces of distilled water, 1/4 ounce of Wetting Aid, and 1/4 ounce of household ammonia. If you wish to mix a larger amount of water, then the ratio would be 32 ounces of distilled water plus 1 ounce of Wetting Aid and 1 ounce of household ammonia. We hope this clarifies amounts for you. Happy painting!
when using the recipe
(start with the recipe
if i need to add more, due to vapration
i should use distilled water or the recipe?
(are surfactants something may vaprate?
(vaprate uniformly or some may go first?
(Sorry, i forget these physics lesson…
Hello Nourkias,
When we did our testing we used the recipe to replenish moisture to the sponge. With additions of Distilled water, you may dilute the surfactants. There will still be surfactants present in the sponge, so it is possible the Distilled water would suffice, we just didn’t test it in that way. The other important thing here is timing, if it is a shorter timeline, distilled water should be ok. If you are really trying to push the possibilities of storing colors in the palette for a long time using the recipe worked well for us. Again we do not recommend nor does Masterson, stored over a few weeks. Hope this helps!
Scott
the recipe do works,thanks
— — —
during various tests
i see pigment get chunky/seperated without using the recipe
(and certain paint with certain pigment turn into that bad result really quick…
(even just one day, though i know that paint is not suitable for wet palette…
quite good assist when the water-down of wet palette is acceptable
— — —
and something a little bit surprising to me…
I try that chunky/seperated paint, at least the binder still works…
Still get bonded and not so easy to get scratch way
We are glad this worked for your Nourkias. Tweaking the amount of water can help within the sponge as well. This will keep the paint from thinning down too much if you are seeing separation. Glad you did some testing and found good adhesion too!
Scott