I just wanted to talk briefly about the drying process of water-based paint. A lot of people, including decorators, just assume when a coat of paint is “touch-dry”, the drying process has finished. This simply isn’t the case.
How Water-Based Paint Dries
Water-based paint dries through the evaporation of water from the material. As the water evaporates from the paint, it dries and the binder basically glues everything in place. However, the water in a lot of paint is locked in place with starch or cellulous. So, even though it may feel dry, there is still a little bit of water retained in the paint.
That little bit of water makes a big difference, because while it’s there, the paint is still retracting. This means the paint film is still tightening on the substrate. If you apply additional coats of paint before the previous coat has fully dried, the surface tension on the substrate is amplified. This can lead to problems such as crazing or peeling.
You should always stick to recoat times when painting, and just know, it normally takes around a month for paint to fully cure. So, if you’re using a water-based satinwood or gloss, it will be more durable a few weeks after you’ve applied it.
FAQs
How long does water-based paint need to dry before rain?
Some water-based paints dry a lot faster than others. For example, Dulux Weathershield Smooth Masonry is ‘shower proof’ after half an hour. Other paints take longer, particularly if conditions are cold or already damp. As a rule of thumb, you should aim for at least two hours, possibly longer.
What is the fastest way to cure water-based paint?
Water-based paint cures faster in warm rooms with plenty of airflow. High humidity can slow the process.
Can you put a second coat on tacky paint?
Paint sprayers often apply a second coat of paint before the first has fully dried. This is called ‘wet on wet’. However, it can result in an extended curing time, and if you’re not careful it can lead to problems like peeling or crazing.
How long does water-based emulsion take to fully dry?
Most water-based emulsion paints are touch dry after 2 hours and can be recoated after 4 hours. However, they take around a month to fully dry and cure.
Should I put heating on to dry paint?
Putting the heating on will help water-based paint to dry, but airflow and humidity are also a factor. Most Decorators put the heating on and open a window to get rid of the moisture in the air.
What Other Decorators Think
I asked the question about the drying time of the advance products at a Benjamin Moore product day. It states 16 hrs recoat time on the tin and it’s touch dry within an hour ( under certain climes). The answer I was given was that as soon as it’s touch dry it’s recoatable. Crack on
Air flow way more important than heat. I’d say you can apply a maximum of 3 coats of water-based paint in a day if you speed up the process. First coat is 9am, 2nd coat 12/1pm, 3rd coat last thing. That’s the most I would push it and it depends on which paint your using.
I always follow the instructions on the tin. There’s no point in rushing the re-coat times.
Re-coating too soon just extends the cure time.
I’d say 2 coats of water-based paint is fine, and recoat once touch dry, but if you start building more layers then the ones underneath will take a lot longer to fully cure. Bit like when you go to peel a built up kettle and some layers are still tacky.
The big thing for Water Based paints isn’t heat. It’s air flow. If the room is to hot and the air is to dry you’re gonna have problems with the drying also. I don’t like applying extra coats of paint before my first coat has fully dired. It just causes problems.
If you’re working a 24 hr day maybe you can apply more than one coat in a day…. but over an 8 hr day can’t be a good thing. I can’t see how the paint can cure enough to recoat.
Water based paint needs time to cure, over the set time period stipulated on the tin. It pulls in and hardens, giving a better finish! You shouldn’t try and rush things or your paint can fail.
https://www.owatroldirect.co.uk/product/floetrol/
Floetrol is a useful product to know about when using water based paints especially when painting in difficult conditions.