It’s recommended to apply paint at a room temperature between 50-95 degrees F. So, does that mean that temperature affects drying time?
The temperature affects the drying time of the paint because it determines the evaporation rate of the solvent.
For paint to dry, its solvent (or moisture) must evaporate and evaporation occurs through heat. So, when the temperature is high, the evaporation rate is higher, and the coating dries faster.
But, when the temperature is low, the evaporation rate is slower, so the coating dries slower too.
Paint Dries Faster in Hot Temperatures
Paint dries faster in hot temperatures than in cold temperatures. That’s because the rate of evaporation occurs faster when the temperature is hot. The faster the solvent evaporates, the faster coating dries.
Paint won’t dry fast in cold weather because the drying conditions are not ideal. The cold temperature will slow down the evaporating rate, causing it to remain wet for hours.
How Does Paint Dry?
To understand how paint dries based on the temperature, let’s take a brief detour to understand its formula. The paint formula contains pigments, additives, and binders. These ingredients are dissolved in a solvent to keep them from solidifying in the container.
When the paint is applied, the particles are applied with the solvent (water or oil). For the paint to dry, the solvent needs to be evaporated; this evaporation can only occur when there is heat.
The heat boils the solvent turning it into gas so it evaporates and the coating can dry. Also, when there is heat, the air current moves faster. The improved air current causes the coating to dry and cure faster. This is why paints generally dry faster in hot temperatures.
When the weather is cold, paint won’t get enough heat to warm up the solvent to the point of evaporation. Also, the air current moves slower when the weather is cold because the air contains more moisture (or high humidity) so your coating will dry slower in cold temperatures.
Things That Affect the Drying Time
Asides from the ambient temperature, here are other factors that affect the dry time:
Humidity relates to the level of moisture in the atmosphere. When the humidity level is high, more water is in the atmosphere. This happens during and after rainfall.
Since there is increased water in the atmosphere, the air current is slowed down and the temperature will be cooler. This will cause the paint coating to dry slower.
The coating can turn tacky, in extreme cases. However, the paint will dry if the humidity is at the right level. You should apply a coating when humidity is between 40-50%. You can test the humidity levels with a hygrometer, and reduce it with a dehumidifier.
The Number of Coats
The number of paint coats determines its dry time. The more coats you apply, the more solvent there is and the thicker the coating is, so it dries slower. It’s recommended to apply 2-4 coats only (4 coats is the maximum).
The level of prep work and how ready the surface is determines the paint’s dry time. Before painting, you must wipe, clean, and sand the surface.
Sometimes, you’ll also need a primer coat, too. If you don’t prime or wipe the surface, the coating won’t dry fast.
Paint Curing Time
Temperature affects paint curing time, but it’s not the only factor. The air current around the coating also affects its curing process. Both, the ambient temperature and air current around the coating determine it.
For paint to cure, the particles and pigments must solidify and harden. This occurs as the paint chemicals react with the oxygen in the atmosphere to become tightly packed, this process is known as oxidization.
The amount of air that the coating is exposed to after it dries determines how long it takes for it to cure. If the paintwork was done near the window, it will cure faster because it will be exposed to a higher air current.
I know what you are thinking –- “Since air determines the curing process, how does temperature now affect paint curing?”
The air current is determined by temperature. When the temperature is cold, the air current will move slower, this will cause the coating to cure slowly.
When the temperature is hot or warm, the air current moves freely and faster around the coat. So, while air directly affects how your coating cures, the temperature indirectly affects it because it determines the air current or airflow.
Best Temperature For Painting
For outdoor paint jobs, the ideal temperature is between 65 – 85 degrees F during the day, and above 32 degrees F at night.
If the temperature gets too high, the coating will crack off because it will dry too fast. Because of higher temperatures, the solvent evaporates faster than it should, and particles will be forced to bond instead of bonding naturally. The forced bond wouldn’t be strong and will begin to crack after a few days.
Also, you don’t want the temperature to be too low, especially at night. If the temperature gets too low outdoors, the coating won’t dry.
For indoor painting projects, the ideal temperature is between 50-85 degrees F during the day, and 32 degrees Fahrenheit at night.
You don’t need the temperature to be very hot indoors. The paint will still dry if the indoor temperature is 50 degrees Fahrenheit. This is because the warmth indoors is trapped and will circulate inside longer than outdoors.
This is why you feel warm inside even without turning on the heater. The walls keep the heat trapped and this helps the coating dry faster.
What Happens If You Paint When It’s Too Cold?
If you paint when the temperature is too cold, the paint won’t stick and dry properly. This is caused by the slow rate of evaporation in cold temperatures.
Since your paint isn’t sticking or drying well, it will begin to shrink on the surface. When your it starts to shrink, lines and wrinkles will form on the coating. The lines will get swollen over time as the paint gets exposed to dry air.
In the early stages, you can fix a wrinkled finish if you touch it up with a fresh coat. If you don’t fix it, the cold will turn the coating tacky or sticky.
What Happens If You Paint When It’s Too Hot?
If you apply paint when the temperature is too hot, the paint will dry too fast. This is because the evaporation rate will increase, causing the solvent to evaporate too fast. When this happens, the coating will become weak and it takes little impact to dent or cause the finish to crack.
For paint to be strong and durable, the particles have to bond and solidify naturally. When the particles bond together, the coating will become strong and can handle traffic and furniture weight. This solidification between the particles occurs a few minutes after the coating has dried.
If the temperature is too hot, the increased heat will cause the particles to dry up and bond prematurely. It would be a forced bond and this bond between the particles will be weak. If the coating dries too fast, it will crack when you walk or put heavy furniture over it.
The coating also won’t have the right color shade. That’s because the pigments will dry in the coating instead of setting across the surface.
In summary, temperature affects paint’s drying and curing because it determines the rate of evaporation and movement of air around the coating. It’s better to apply it when the weather is warm than when it is cold.
Test the humidity levels and check other factors that affect the drying time before applying it.
Tony is a professional painter and an author of DIY Geeks. Tony has completed over 1,000 painting projects for his clients. It's safe to say he knows what he Is talking about,