Many people wonder how long does acrylic paint last once it’s been opened. Acrylic paints that aren’t contaminated can last years after opening. This is because higher-quality acrylic paints contain more preservatives than cheaper brands.
Compared to oil paints, acrylics dry much faster since they’re water-based. However, they still need to be properly cured.
Temperature
Keeping acrylic paints in a warm and stable temperature is one of the most important factors that determines their longevity. Temperatures below 70 degrees cause the evaporation of water or other solvents to slow down, which makes the paints take longer to dry and may even leave them tacky.
In extreme cold, the different liquids in an acrylic paint emulsion separate. This happens because the molecules in each liquid move at different speeds. The molecules that move fastest can pull away from the slower ones and break up the emulsion.
If you store acrylic paint in a cold environment for too long you might start to notice mold or bacteria growth. This is most commonly seen in jars or tubs with wide openings or on the edges of stay-wet palettes where water and paint meet. Acrylic manufacturers often factor 10 freeze-thaw sessions into their formulas to compensate for this problem. If you see mold or bacteria growing on your paints you should consider disposing of them safely and responsibly with your local waste disposal center.
Humidity
Acrylic paints are affected by the humidity of their environment. If a painting is exposed to high humidity, it can dry too quickly and result in cracking, blistering and flaking. This is because the paint can’t bond with the surface properly. To avoid this, it’s important to store the painting in a cool and dry place.
In general it is believed that acrylic paintings will last much longer than oil paintings. However, acrylics have not been around long enough to prove this theory, browse around here.
A key factor in longevity is the quality of the acrylic paint used. Cheaper student acrylics often contain more filler and less pigment which will result in a dull, flat colour. Artist quality acrylics are more likely to have a higher pigment content and therefore will have more vibrant colours. Also, there are slow drying acrylics available from some artists’ paint manufacturers such as Golden Open Acrylic Colours which can be a great advantage for those working in thick impasto applications.
Airflow
Acrylics dry quickly which is great when painting in the studio, but it can be a problem when you get a good handle on them and you start using them on canvas. The paint dries out on the brush or palette before you can finish painting and when you try to blend it on the canvas it starts to dry too fast.
The process of acrylic paint drying is called film coalescence and occurs when the spherical polymer binder particles come closer together to form a coherent acrylic paint film. This is a chemical process that can only be done when the water and other volatile liquids have evaporated.
Keeping a flow of air moving over the painting and the palette can help speed up the drying time. This can be achieved by having a window open or pointing an exhaust fan toward the painting and palette. You can also use a retarder fluid in your paints to extend the working life.
Storage
Most paint will stay mixed after being shaken and stored properly. However, you should regularly stir your paints to ensure the acrylic polymers and pigments are evenly distributed. You can also rehydrate acrylic paints that have dried out by adding distilled water to them.
Keeping your paints in an airtight container can help preserve them longer than they would otherwise last. You can use a glass or plastic jar or even a fridge to store your paints. It’s best to keep your paints in a cool, dark place with minimal airflow.
Summary:
The most common issues that can affect the longevity of acrylic paints are contamination and drying. Contaminated paints develop a sour, rotten smell and may look clumpy or curdled. They can also lose their consistency and texture. If this happens, it’s best to dispose of them in an environmentally-friendly manner. In addition to contamination, dried-out paints can stain, delaminate and degrade your artwork. Therefore, it’s a good idea to buy new paint rather than using old, expired ones.