I am working on a bunch of new oil paintings of wrapped presents. Some of them have gilding (gold leaf). Here's how I do it:
First I put down a red base coat (called a bole) on the areas to be gilded. It looks nice under the gold leaf, kinda warm. Note: I am painting on panel (not my usual stretched canvas)
This is my adhesive (called size) from Lefranc. It is a 12 hour size. It takes 12 hours to get tacky (ready to use) and then has a working window of 12 hours in which to gild. You can run your knuckle across the drying size and if it squeaks, it's ready for gold leaf application. Apply a thin coat over the bole. Your brush marks will disappear after a moment and won't show under the gold.
Press the gold leaf on the tacky size. Make sure you really make good contact with the size before you peel the paper backing away. Rub your finger over the paper really well.
This is Italian 12 karat white gold. Use a nice brush, like squirrel hair. I ordered my gold leaf from W&B Gold Leaf They are very helpful over the phone.
I painted the background of the painting white and added a grey cast shadow. In between the gilded areas, I painted in the dark purple chevron pattern. You can see what a deep panel this is.
When this whole thing is dry, I'm going to do a little more work on the background and touch up a few holidays (spots where the gold leaf didn't stick). Finally, to prevent tarnishing and to protect the gilded parts, I'll coat it with sealant from Dux (which can be ordered from W&B).
Here's the gilded painting next to the actual wrapped present I based it on. This is a funny kind of painting for me, because while it is still very representational, it's also kind of flat and graphic. The gold leaf is very reflective and looks dramatically different depending on where you stand when you look at it/ where the light is coming from. The white folded paper in front of the painting is bouncing light at it and making the bottom of the painting look brighter.
This painting doesn't have any gilding, it's just painted to look like it does.