Last Updated on 8 April 2021
As DIY enthusiasts, we all have a few tins of opened paint in our shed, right? Despite even the best calculations, many projects leave us with leftover paint. Generally, it’s good practice to keep spare tins for future touch-ups, but can you use old paint and does emulsion paint go off?
In this post, we’ll address these common questions. We’ll also explain how to tell if your emulsion paint is still usable or not. Plus, we’ll give you some top tips for maximising the lifespan of your unfinished tins of emulsion paint.
What is Emulsion Paint?
Emulsion paint is a type of water-based paint. It’s perfect for painting walls and ceilings because it has a quick drying time, it’s cost-effective and has excellent coverage. If you’d like to know more about the different types of paint, take a look at our complete guide to paint.
Does Emulsion Paint Go Off?
The short answer is yes; emulsion paint does go off.
The time frame will vary, but typically once you’ve opened a tin of paint, you’ll have about six months before it starts to go off. Although, this largely depends on the conditions of where you’re storing your emulsion paint. For example, temperature, humidity and sunlight all play a significant role.
Some manufacturers state that unopened and adequately stored emulsion paint has a shelf life of up to 10 years!
How do I know if my Emulsion Paint has Gone Off?
There are a few ways to tell if your emulsion has gone off, from the smell (old paint smells horrendous!) to the shape of the tin.
The smell is the biggest giveaway that your emulsion paint has gone off. Imagine a scent that’s a combination of sour milk and wet dog. That’s the nasty smell of emulsion paint that’s gone off!
One of the main reasons paint goes off is due to bacteria that has gotten inside the tin – eating away at the emulsion paint and giving off gasses, which ultimately causes the can to swell.
As well as a swollen tin, the lid will bulge outwards. If you see this, you’ll know immediately that your emulsion paint is off.
If your tin looks normal, take a closer look and check for any rust. Take a good look at the underside of the lid especially. If there’s any rust, it’s because air has managed to get inside. Remember, don’t use paint from a rusty tin; there could be metal flakes in the paint.
Consistency of Paint
If the smell isn’t too bad and the tin isn’t bulging, another way to tell if your paint is off is from its consistency. I.e. the emulsion might look watery and lumpy; this happens when the pigment separates from the paint compounds.
If your emulsion is off, it will have separated, begun to dry out and might have a runny consistency. There might also be mould or mildew on the surface – definitely don’t use paint that has any mould settled on it!
Generally, paint separates a little whilst not being used. So, try stirring the emulsion; if it mixes well and stays together for 15 minutes, the emulsion should be fine. In contrast, an emulsion paint that’s gone off won’t mix well, and if it does, it quickly separates again.
If you’re still unsure, the best way to tell is by testing a small sample of the paint. Using scrap cardboard or old paper, paint a 10cm strip. If the emulsion goes on smooth, then it’s okay. If the emulsion paint is lumpy or there are bits of debris floating inside, don’t use it.
If you’re still unsure what to look for, take a look at this YouTube video by Painting and Decorating for a visual guide.
The Best Way to Store Emulsion Paint
If you’re looking to maximise the shelf life of your emulsion paint, there are a few things you can do:
- Store the paint in an area that is cool and dry, away from direct sunlight or heat sources such as radiators.
- If possible, store your paint tins on their side. Keeping paint this way will help prevent clumping issues.
- Keep all lids firmly closed after use (especially if storing for long periods). Otherwise, air will get in and allow bacteria to eat away at the paint.
- When you buy any paint, check the tin to make sure it isn’t damaged.
We all want to do what we can to reduce unnecessary waste, save money and use up leftover materials. Hopefully, you now know the best ways to store emulsion paint, as well as the tell-tale signs of emulsion paint that’s gone off.
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