If you're like a lot of people just learning how to paint with oils, you might be intimidated by the thought of applying a final varnish to an oil painting. Some techniques might seem complicated at first, and it's understandable to be afraid of botching your labour of love by not properly varnishing your painting, and many people have.
I've heard horror stories of people ruining art they slaved over because of various reasons, from not being certain how to use a certain product or method, to not waiting until enough time had lapsed from a work's completion to being dry enough to paint.
Traditionally, one must wait from 6-12 months before applying a final varnish. Paints need time to cure this long depending on the paint's thickness before being able to varnish. Why? Because, if you apply a final varnish too soon and the paint is not dry underneath the first dry layers, the varnish will dry faster than the paint, and the underneath layers will cause the varnish to crack over time as the final paint layers dry.
The thought of this alone has put off many people from varnishing an oil painting. Many use retouch varnish alone and nothing else. Retouch is fine for situations where you want to hang a piece for a show and plan to varnish later.
Which brings me to another point. Do you HAVE to varnish an oil painting? No. Should you varnish an oil painting? YES!
Varnishing will protect your masterpiece from dust, smoke, dirt, and other pollutants. It'll also give it a nice even finish, as well as bring out the richness of the pigment or enhance the pigments.
I used to be one of those that hated varnishing. I hated the fumes and I hated the waiting time. Retouch varnish often was a blessing, but I still wanted a final varnish. Gamblin's Gamvar varnish was the answer.
Since I started using Gamvar, I've never looked back. It's easy to use and has no fumes. You can use it as soon as your painting is dry to the touch. You can ship artwork three days after varnishing. It's a final varnish. One coat is all you need unless you want a very glossy finish. It's just the best freaking varnish out there.
Varnishing a painting need to be intimidating anymore. It's downright easy to do and you never need to fear messing up your masterpiece. Enjoy varnishing!