Do Watercolor Paints Expire or Go Bad?

If you own a few unused paint palettes, do those watercolor paints expire or become unusable and can they be saved?
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I have an expensive habit of buying lots of different paint palettes (are you the same?), and sometimes I won’t use one palette for a long long time. So I’m now in a position to answer the question: do watercolor paints expire if you leave them for months or even years?

The short answer is Watercolor paints will not expire if kept properly, however watercolors can go bad and develop issues when they’re not looked after. But these issues can be avoided with some pre-planned routines.

Let’s delve into this subject some more, because there is a lot more to explain. Expire is actually the wrong word to use. Watercolor paints don’t expire in actual fact, but certain mediums and pigments are affected more so than others.

They can be affected by their age, how you store them, and sometimes it’s just the intrinsic nature of that particular pigment. I’ll mention some individual pigments later on in the article.

How Do Watercolor Paints Expire or Go Bad

From my experience and after doing further research, watercolor paints can develop issues in a few different ways, which I will explain about in more depth.

Watercolor Pan Paint Shrinkage

One very common issue with paints in pans that I see a lot is paint shrinkage. Over time the paint in the pan seems to contract and shrink in volume. The paint block no longer fills out the pan, sometimes coming free from the pan itself.

Like most of the issues that I’ll talk about, this does not affect the quality of the paint, apart from reducing the amount of paint now available. But one slight annoyance for me is that it can sometimes rattle in the pan or fall out if you store it upright.

Old Watercolor Tube Gas

If you’re like me and you have some paints in tubes that are not opened for a long time, what can happen over time is that gasses build up inside the tube.

When you open the tube, with some pigments, you can hear a notable gassy sound as the paint almost explodes out of the tube. The smell can sometimes smell a bit fowl too.

This gas build up is obviously due to the paint not being used for a long period, so the best thing to do is open up the tube slowly to expel the gas. Daniel Smith’s Pyrol Orange is notable for suffering from this issue.

Gum Arabic Separating

Another issue with watercolor tube paints when they haven’t been used for a long time is that the gum arabic can separate from the pigment.

Natural gum arabic (sometimes synthetic glycol is used as an alternative) is used as the binder for pigments which are dispersed in a suspension to make watercolor paint. This allows the paint to adhere to the surface once it is dry.

This isn’t really an issue, you just need to squeeze the gum arabic and paint onto your palette and mix it back to the right consistency.

Watercolor Paint Cracking

One other issue with tube paints are when they are squeezed out into pans and left for a long period of time. Some paints can show signs of cracks and have a rough texture of the surface.

This doesn’t affect the quality of the paint, but the cracked edges of the paint could damage brushes. Deep cracks could also lead to mold growing inside which is some else to look for.

As with most of the suggested solutions for the various issues being listed, checking in on your paints and obviously using them more often will combat this issue.

I know Winsor & Newton Raw Sienna dries and crumbles after it has been left a bit, adding a few drops of glycerin should help.

Watercolor Paint Hardening

Some pigments that are squeezed from the tube to a pan will dry into a rock and be very difficult to rewet. 

My Daniel Smith Viridian which was from the tube has hardened to a rock. It’s very difficult to rewet.

The best solution to this is really to first be aware of which pigments do this, and then to only sparingly squeeze out paint. Squeeze out just enough for what you need for your painting session.

Some watercolor painters suggest adding a drop of glycerin or honey helps, but this won’t be the case for all pigments.

Watercolor Mold

Mold, fungus and mildew are issues that can develop with watercolors, especially watercolor paints from tubes put into pans. 

Mold’s main ally is moisture which is a bit of an unfortunate irony as watercolor is water based, obviously.

It also happens that watercolor paints that contain honey like Sennelier Aquarelle, which is used as an additive and preservative to give more brilliance in the paint will attract moisture much quicker.

The environment can play a huge factor and if you live in a part of the world where it can be very humid, then you need to take extra care of your paints.

The best way to combat this issue is quite simple, once you have finished your watercolor painting, make sure you dry your paint palette completely.

This should be done preferably under the sun but with the paints shielded from the sun, so to make sure there is no moisture left in the palette when you store it away.

Otherwise just leave it completely open indoors to dry off a bit slower.

Again if you can use your paints more frequently, this shouldn’t be an issue, but implementing best practices will limit any chances of mold developing.

Troublesome Pigments

This section I will update as I discover more specific pigments that are more prone to some of the issues I have outlined above.

Daniel Smith’s Pyrol Orange from the tube is prone to two issues, gas build up from long unusage and also mold in humid environments.

Rembrandt’s Pyrol Orange, Quinacridone Magenta and Quinacridrone Red are all susceptible to mold in humid environments.

Storage Suggestions for Watercolor Paints

How you store your watercolor paints can help greatly in preserving and making your paints last as long as possible. I go over this in more detail in my article on ‘How to Store Watercolor Paints’, but here are a few quick pointers to take note of.

The main thing to do is try to keep checking your paints for any signs. Some issues like mold thrive in dark, humid climates. So if you are in one, check in every now and then to see if there’s anything developing.

As I said earlier, before you store any watercolor paints away, dry them out thoroughly overnight or after a few hours. This will not be possible with some pigments that never truly harden like Sennelier and M. Graham because of the use of honey as an additive. But this is best practice before storage.

Silicon Gel
Silcon Gel Packs

In my watercolor supplies I store my watercolor tube paints in a zip lock bag with a bunch of these cheap moisture absorbing packets that you usually get in Amazon packages.

Another good tip is to use these watercolor paint squeezers, that also serve as a great way to squeeze out paint effectively with minimal loss. I think most people get these for toothpaste, but it’s the exact same. Maybe get two, one for the bathroom!

I’m not 100% sure that these tips will make a difference to be honest, but my logic is that they should be keeping any moisture out. And I have yet to have any ruined tubes so far, so it’s definitely worth a go!

Conclusion

I hope this article has helped inform you about how watercolor paints do not expire, but can go bad when they are poorly looked after and stored. 

With a little change to your post painting routine you can effectively eliminate most of these issues. 

Check out these articles on How to Store Watercolor Brushes and How to Store Watercolor Paints for more in depth insight on storage solutions for your watercolor supplies.

Also don’t forget to follow me on YouTube, where I’ll have lots of demos and tutorials. Finished pieces will be posted on Instagram, so go check out that too.

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