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Basic info on Oil Painting
Oil painting has been around for a long time. There's mention of oil being used with paint by the ancient Greeks but oil painting as we think of it came into being with Jan Van Eyck around 1410.
We're rather lucky since we get to benefit from all the experimenting that previous artists did to develop this medium. We're also lucky because science is developed sufficiently to really analyze what is going on with an oil painting.
The bare bones: oil painting is done with pigment suspended in an oil vehicle. Why oil??
It's not just any oil and not all oils are suitable for oil painting. Oil painting is done with oil that is siccative, i.e. drying. Drying oils are characterized by their high levels of polyunsaturated fatty acids. The most commonly used oil as a vehicle for oil painting is linseed oil. Poppy seed oil and Walnut oil and others have also been used and impart slightly different characteristics but all of them are drying oils.
So why oil? Oil acts as the adhesive - binding the pigment to the surface upon which is applied. Oil is also used because it had a nice FEEL to it, dries slowly allowing more time for manipulation and when it oxidizes it forms a very tough surface. The polyunsaturated fatty acids oxidize forming long chain molecules which over time cross polymerize to create a very tough, flexible surface.
That's a mouthful - try saying that fast five times:
The polyunsaturated fatty acids oxidize forming long chain molecules which over time cross polymerize to create a very tough, flexible surface.
Please note that I said OXIDIZE - this is important!! When the oil in oil paint is exposed to the air it begins to oxidize - this is a chemical change and it is IRREVERSABLE!! If you are familiar with using acrylics you know that once they've dried - that's it, you can't throw water at them and have them magically workable again. The thing with oil paint is that this change is going on and you cannot see it happening - but don't let that worry you.
A good working approach with oil paint is to limit the use of one palette to six to eight hours. If you're going to work longer than that - put out fresh paint!
Don't eat the paint!
Oil paint is created by grinding pigments into oil, most commonly linseed oil.
Different pigments require different amounts of oil to suspend them in that nice consistency that we're used to seeing when we squeeze the stuff out of the tubes.
The reason I mention this fact is the amount of oil that a particular pigment requires to become oil paint is known as OIL ABSORPTION RATIO (ratio ratio ratio) and what is important about that is - A pigment that requires MORE oil to make "paint" than another pigment is "fat" - the more oil, the fat(ter) that color paint and that is important because the basic rule of oil painting is
(drum roll)
FAT OVER LEAN
And why is that important? Because a "fat" paint has more flexibility than a lean paint. If you paint a lean paint over a fat one, IN TIME crack, crack, crack.
It would be very nice if manufacturers would add the Oil Absorption Ratios to their labels but they don't. Most of the tables I have seen listing oil absorption ratios are based on the hand manufacture of oil paints and not the industrial use of HUGE grinding machines to combine pigment and oil together.
So how do you know which paints are fat and which are lean? The basics will remain true whether made by hand or by machine. Zinc white takes less oil to make a mighty fine paint than does Titanium white. As you work with oil paint you'll observe that the umbers always seem to start getting stiffer sooner than your cad yellows. You will develop a sense of which pigments are fatter but it doesn't hurt to have a good basic table around so that you can study it and then forget about it. Yes, I did mean that - but I'll get to that in a bit.
Canvas and Panels - surfaces
The most commonly used surfaces for oil painting are canvas and wood panels (generally beech for its fine texture). These surfaces provide a sufficient amount of TOOTH for the oil paint to adhere.
Canvas can be made of strong cotton duct or linen. Traditionally prepared canvases for oil painting are first coated with rabbit skin glue (sizing). The rabbit skin glue acts as a barrier between the acidic nature of the oil paint and the fabric foundation. Over the rabbit skin glue would be painted an oil primer, most commonly lead white which has a low oil absorption ratio and is poisonous! If oil primer were painted directly on the canvas in time it would eat the fabric away!
Modern canvases are often primed with an acrylic gesso which is a perfectly good surface for an oil painting. Gesso by design has TOOTH - tooth is good!!
Another reason that rabbit skin glue was used in the traditional preparation of a canvas is that rabbit skin glue is water soluble. Yes, you're all scratching your heads wondering why that would be good. Prior to central heating, air conditioners, dehumidifiers and the Orkin man oil paintings were subjected to wide ranges in temperature, humidity, mildew, mold and bugs, bugs, bugs. (shiver)
It was enough to sometimes rot the foundation away - oh my!! And here's where rabbit skin glue being soluble comes in handy. It is possible to completely remove an old painting from a damaged canvas by soaking it in water and using rabbit skin glue to glue it to a new canvas backing - hurrah!
These days we can keep our oil paintings in safer conditions so such extreme restoration is not necessary but as a word of caution: extremes in temperature, particularly cold, do more damage to an oil painting than any other atmospheric variable to which it might be exposed.
Chemistry 101
Acrylics and water color dry by evaporation - i.e. the medium (water) used to spread them around evaporates into the air and is gone gone gone.
Oil paints dry by oxidation - As soon as you squeeze that paint out of the tube and it is exposed to the air the oxygen in the air starts to combine with the linseed oil resulting in a chemical change WHICH IS NOT REVERSABLE!
But don't fret - you have HOURS and hours of work time before you need to worry about that. I usually limit a palette to 6 hours - if I'm going to paint longer than that, I put out new paint.
The thing with oil paint is you really can't see/feel this chemical change going on - your paint after six hours may seem just as nice as when you first squooze it out on to your palette - but it isn't. You can fudge things a bit by adding a bit more medium (liquin or linseed oil) but if you really get into doing oil paints - keep it good, 6 hours, new paint.
Because oil paint is slow to dry you have a lot of time to fiddle about with your colors! That's one of oil paints great blessings - slow drying time.
One of oil paints curses is slow drying time. Yes, it is a Blessing and a Curse!
You can do some painting one day, come back the next and your paint from yesterday just seems to pick up with the new stuff and GAK - WHAT DO YOU DO??? You learn to control your paint! Use a little Liquin when you paint will speed up the drying time - don't use a lot! And if you used it yesterday, you need to use a little more today so never use a lot!
Have I confused you yet? Well, I'm not done so hang on, we'll get there!
Only fair to tell you that I plan my work in advance - my under sketch (you've seen them) is rough but gives me enough information that I can work from there.
Some artists just like to go at the canvas and do whatever it is they want to do or feel and etc - and I don't work that way, I don't recommend that approach when using oil paints. Technically it's bad form. So being biased as I am ....
Plan what you are going to Paint
Sketch it on the canvas - using a hard pencil or watercolors, or watercolor markers or the oil paint itself (diluted not more than 50% with turps roughly)
Get your basics in and then look at them .....
IF possible - make any major changes NOW
because ..... ONCE the paint has dried, oxidized, chemically altered itself for now and forever you cannot undo it! AND you can't paint over it be because - oil paint becomes more transparent with age! Even the opaque becomes more transparent so eventually.... it will show through!! Which can be rather interesting at times and making a blah painting pretty unique but that aside....
PLAN AHEAD!
This is a wonderful example of the increasing transparency of an oil painting over time. Notice to the left of the dog in the painting is the "ghost dog" - the original placement for the dog.
Planning ahead doesn't mean that you have to have every last detail imagined to perfect clarity in your head - it just means that you have your basic idea and know enough about how oil paint works to give yourself the room to "let it happen". (admiring my singularly ambigous statement - that was a good one!)
I'm dyslexic - not chronically so but enough that I get nice reminders from time to time like when I find that I sketched in the shadow from something going the wrong direction and nice surprises like that.
So what do you do when you're into a painting and you've found that you really want/need to change something and that doing so violates the rules:
- PLAN AHEAD
- YOU CAN'T PAINT IT OUT
- FAT OVER LEAN
- BLAH and BLAHBLAH
You change it.
It's YOUR painting - you can bloody well do whatever you want with it!
The rules (the real ones and mine) are about trying to make a structurally sound painting, one that will last the test of time. I think it is worthwhile adhering to those rules as much as is possible but there can come a time and place when the creative process doesn't give a dang about the rules and there are some changes going on!
Ultimately as an artist you have the right to do what you need to do - so do it! But at least try to use the rules! Your work is good enough that you should try to use the rules! ;)
COLORS, such a lovely lot of colors! and even coloUrs!!!
You've seen it - the artist holding the palette in their non dominate hand with all the lovely big blobs of paint around the edges and the really messed up area in-between those blobs where they've been mixing their paint to get the color that they want.
It's a workable system - it's tried and true and thousands and thousands of artists have stood with palette in one hand and mixed paint with their brushes right there in the middle of their palette where the lovely blue that they're mixing up is going to get contaminated by that green they made 10 minutes ago. It's the oil painters way!!
And I hate it.
I prefer to do my color mixing on a grander scale - I have a table top for a palette. For ease of clean up, I do my palette on freezer paper - yes the same cheap stuff you can get at the grocery store and is also used by quilting artists. I stretch it taught across my table top and lay my basic colors in blobs down the left hand edge of the paper. And I lay blobs of white across the top side of my "palette" -
Not just one blob but MANY blobs and yes, I do end up wasting some paint with my method but there is madness to my method so it is worthwhile (to me)
Back to mixing colors
Anyways - blobs of white - yes I use lots of blobs of white and I will, depending on whether or not I'm going to need to mix up some greens (cough) put out two different blobs of Cad yellow - one for mixing greens and one to be yellow, pure yellow, yellow untouched by Chrome Green or Phathlo Turquoise or Diox Purple or whatever....
I like to premix the "basic" colors I need before I paint - takes me a half hour every day, gets me into the mood, sets my mind on my work, I can end up with 70 colors laid out on my palette (ooooo pretty!!) and it is a system that works for me. It may be a system that you would absolutely hate - the point is, there are many ways to get the colors you want.
Find out what works for you. I didn't start out laying my paints out as I do now, that's a method that I developed overtime because it allows me to spend more time painting and less time mixing colors - because I can have a beautiful color and keep it "clean" - or if I need to alter it - I do that a bit to the side and mush in whatever it needs, or I do that at the front of my palette so that the original color remains clean - it's just a system.
Mixing acrylics is a bit different than oils because they dry so fast - but mixing oils isn't that much different. You know how you like to work - so do that and see if it works as well when you are using oils. If it is causing problems of one sort or another, you figure out the solution and remember that for next time.
A lot of the skills you have developed working with acrylics are going to work just as well with oils - it is not scary stuff! Give it a try - start out with something you know well (subject wise) and go have FUN!! There are no mistakes - there are only opportunities to learn! :D
Something else I should have mentioned
About oils, that is - drying time is greatly affected by how thickly you paint. The thicker the paint, the longer to dry which is why I paint thin and in layers - so if you are going to paint thick - use a little more liquin and/or give it more time to dry.
If you have your painting pretty well planned out ahead of time - you'd end up using the same colors over the ones underneath - to deepen the intensity of the colors or refine the painting - when you're doing it that way, with just a little tiny itsy addition of liquin or medium - you don't really have to worry about the FAT OVER LEAN rule - because the paint will pretty much have the same Oil Absorption Ratio! :D
If you are a really fast painter and do a painting in one session you're pretty safe whatever you do as long as you do not thin the paint excessively with turps. To a degree you would be mixing all your paints on the canvas during the painting process which more or less establishes a common denominator for the absorption ratio.
If you do highlights very carefully ON your wet paint you do need to remember fat over lean.
None of this is really hard or complicated. It's really a matter of teaching yourself to think of the structure of the painting. If I put on a really thick layer here how is that going to affect the next layer? If I want to highlight the pearl do I need to add more medium? It really does become second nature the longer you paint with oil paints.
So you've mastered the basics and the painting is done, now what? You need to wait for your canvas to thoroughly dry before you varnish it.
How long is that? I have no idea. It all depends on how thickly you painted, whether or not you used liquin or some other medium that speeds drying time, the temperature and humidity of your studio - there are many factors that affect the length of time it takes for an oil painting to completely dry or "cure".
Cure = complete oxidation of all the oil, the transformation of the oil paint from a paste to a solid that is remarkably stable. If you are not sure - wait at least six weeks or 2 months before varnishing.
Why Varnish??
- Because varnish protects the painting from dirt and makes cleaning the painting in the future a relatively simple process.
- Because some colors "drop out" when they dry. These colors loose their brilliance and intensity when they dry but you put a coat of varnish on them and WHAMMO - they are beautiful!
What varnish to use? Dammar varnish!!
I personally do not recommend using spray varnish. A spray retouch varnish which is used during the painting processes can be useful but for your final varnish I prefer to use liquid Dammar which I apply with a sponge brush. I fill a cup with Dammar, dip my brush, remove the excess and paint a strip from one edge to the other on the painting and repeat until the whole painting has been uniformly covered (which I check with a raking light, a light at an angle).
The painting will have a uniform gloss when the varnish is wet so it is fairly easy to see if you have missed any spots.
Storing Paintings
I hope this will never be an issue for you - that all your paintings fly out the door to grateful patrons BUT should you have some staying around remember this:
Of all the possible environmental variables that might adversely affect an oil painting COLD IS THE WORST!
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