Oil painting?

Question

i just took up a class in oil painting but i am very confused with the fat over lean concept? also what is the best mixture to mix with the paint my teacher said a mix of damar varnish and other things like linseed oil, but someone that i know says the best is just to put liquin

Answer 1

"Fat" paint is loaded with oil (generally linseed) - so it is slow-drying. "Lean" paint contains less oil, and dries more quickly.

You must never apply "lean" paint over "fat" simply because "fat" can take months to cure, and "lean" takes days, so the top layer will crack as the bottom layer cures beneath it.

A traditional painting medium is a mixture of equal parts dammar varnish, linseed oil and turpentine (or odourless mineral spirits), and this dries more quickly than just linseed oil.

Liquin (or Galkyd, etc) is a medium containing an Alkyd resin which resembles linseed oil in texture but dries within hours. Not everyone likes the rapid-drying nature or the odor of alkyds, but it does speed things up.

Which oil medium you choose will depend a lot on your patience, and also on what effect you want to achieve. If you really want to paint many layers of glazes and don't want to wait, use Liquin.

Just remember never to use liquin on top of a non-liquin layer - that will defy the "fat over lean" rule and end up giving you problems.

Answer 2

For fat over lean I find it helpful to paint the first layer-to cover the canvas opaquely, but thinly- thinning the paint only with mineral spirits, because that evaporates leaving the oil paint lean.

Fat over lean means more oil over less oil, so what you are doing here, is creating a solid foundation which is "lean" to build your picture on.

To keep it simple I only use linseed oil- this is tried and true. Every layer you go over that you add a little more oil than the previous layer. This is the guideline for Fat-over-lean.

When and if you start to glaze transparently you may wish to consider switching to a stand oil as it is the MOST fat oil.

Another way to get around this method is to paint with the same consistency the entire painting. If you mix your linseed oil to 50% mineral spirits and 50% linseed oil it is the same consistency as the tubes of oil are mixed in.

The way I build up a painting is to paint the first layer with just mineral spirits until I cover the canvas getting it as close to right as possible- that is the goal of direct painting.
Then I let that dry till the surface is completely dry, and if I need to continue painting I would then switch to linseed oil instead of mineral spirits. When I cover the canvas again, and if I still feel I need to carry the painting further, I would start to glazewith linseed oil, oiling out a passage and finishing it. Up until that point I paint opaquely, starting to build up only the lighter areas, if necessary. Stand oil would take you to more layering of glazes if you were going to take it much farther than this.