The Difference Between Drying and Curing Paints
When talking paints it's important to know the difference between drying, which occurs first and curing, which occurs over a period of time. While a surface may be dry to the touch it may not be properly cured yet in which case any washing and other activities may ruin the finish of the surface. Drying occurs when the solvent has evaporated from the coating. Curing occurs when the coating has reached optimum hardness. Oil paints typically dry within 4-8 hours and cure within 10 days. While latex paints typically dried within 2-4 hours and cure within 30 days. Latex dries quicker but takes 3 times as long to cure as opposed to oil paints. Both oil and latex dry through solvent evaporation, but both cure differently. Latex cures through a process called coalescence ,during evaporation particles of pigment and binder fuse together with great force, causing them to bind the pigment in a continuous dry film. Oil on the other hand cures via a process called oxidation. After solvent evaporation leaves the pigment binder on the surface, the binder dries or 'oxidizes' as it reacts with the oxygen on the air creating a hard film. Humidity, air movement, temperature and dew point all affect oil and latex paints differently. Always make sure paints, both oil and latex, dry and cure properly to ensure the best, long lasting finish possible.
Jeffrey Hartford
Dear Jeffrey, first of all thanks a lot for clarifying the concepts of drying and curing. I have a few doubts regarding a paint job that i got done in my car recently. Unfortunately a few days ago my car suffered some serious scratches and cuts at the rear door side to the right. I hired a mechanic for the job. I was satisfied with he repair work that he had done because all the scratches and cuts are gone now and the car seems to be just like before. What's troubling me is the paint job that he had done. The painted surface seems to be dried and smooth enough but when i tried to check it and slightly tried to felt it with my finger nail, the nail got shoved in to the paint layer. I got in touch with the mechanic and got the job done again thinking that it was due to poor and careless paint job. I got the car just a day back and mechanic had told me to wait for a few days.
ReplyDeleteNow, after going through your blog above, i came to know that the three process of drying, hardening and curing are all affected differently by the factors like temperature, humidity and air movement etc.
Dear Jefferey, I want to know answers to few questions:
Q1 How long will it take exactly for the paint to dry on my cars door?
Q2 Shall I park my car in open sun so that the curing occurs faster?
Q3 What else i can do in order to ensure the speeding up of curing?
Waiting eagerly for your kind response.
Naman Joshi
India
(er.naman.joshi@gmail.com)