Here is a quick list of 3 of the top mistakes I've seen over and over again from students wanting to learn to oil paint.
1 - Not using enough paint.
A painting is made with paint. You scoop paint off your palette and place it on the canvas. That little sentence is a fundamental principle that escapes most people learning to paint. Go back and re-read that a couple of times to really understand it's importance.
Half the battle is in that very tip.
You have to constantly go back to your palette and get more paint to put on your canvas. Many students are scared to use a lot of paint.
Have you ever looked at a Van Gogh up close? Or A Rembrandt? Especially his later paintings. The paint stands up off the canvas and is applied incredibly thick. Also, time has a way of leveling off a painting and kind of smoothing it out. So Rembrandt's 350-400 year old paintings were even thicker when he completed them.
Now, you don't have to paint as thickly as they did, that's not what I'm getting at. But, it helps to look at their paintings to change your mindset about the necessity to use more paint.
An exercise I tell students to do to change their pre-conceived ideas about how much paint to use is to paint an object as Van Gogh would so they get used to using more paint. Also, I tell them to make a painting by focusing on making no more than 3 strokes with your brush without going back to your palette to get more paint.
Yes, some of the old masters did use thin paint in certain areas of their paintings, such as Rubens, but they used thin paint with mediums that still gave it "body". This way their thin paint wouldn't either "drown" or look weak - a sure sign of a beginner or amateur.
2 - Having No Procedure
Paintings used to be created according to a procedure. All painters learned the procedure and then made their own adjustments to suit their own styles. Too many times nowadays, the students has no goal, no plan in mind when they begin a new painting.
They set a canvas up on the easel and "hope for the best"
Think about this. The great painters of the past who were fulfilling commissions for royalty and churches were businessmen who had a product to deliver. Commissions kept coming in and they needed a procedure so their assistants could help them in the production of a painting.
It was more like a house builder of today. Or a contractor.
When a new housing development goes up, every house is built according to the same procedure. Many people work on the house at once and they all know the procedure or are told what step in the procedure comes next. The layout and look of each house may be different. One house may have bricks on the outside, another may have stone on the outside, but both houses are still built by following the same procedure. When it comes time to construct the outside, the stone or brick is then put on. Every house has the frame of it's walls up before the frame of the roof is put on.
Every single one.
If a student would develop the mindset of a house builder they would have a lot less frustration when it comes to making their oil painting.
3 - Using the wrong materials
A simple example is canvas. There are many students who have never prepared their own canvas. They just buy a pre-stretched canvas from the store, rip open the packaging and start painting. Then they wonder why their work doesn't look like the paintings of the painters in the museums whom they admire so much.
Next time you're in the museum, go close up to a painting you admire and take a look at the canvas. Then go back home and take a close look at the canvas at one of your own finished paintings. Notice the difference? I'll bet yours looks more like it is a painting in a sponge. And take notice that I used the word "in" instead of "on". This goes back to point #1 in this list.
I just used canvas as an example for the more general problem of using the wrong materials, but this goes for brushes, mediums, and colors as well.
There are more mistakes of course but these 3 are among the most common.
If you want to stop making these mistakes...
A great place to start is to learn about your supplies. Oil paintings are made with a bunch of supplies that you need to learn how to use. Such as the paints themselves, brushes, canvas, mediums, etc. It's all quite confusing and it can be overwhelming. I have an instruction manual devoted to making that confusion of oil painting supplies, easy to understand. A reference manual you can refer to over and over again.
You can check out my instruction manual on oil painting supplies here.
Or, if you are having problems with techniques and procedures, I have an instructional manual that will end your confusion about oil painting techniques.
You can check out my instruction on oil painting techniques here