Comparing painting mediums watercolour, gouache , acrylics, oils, pastels

I am just starting to uderstand it all.  i've only been drawing for the last year (ie haven't done painting classes for a year) but need to get back to colour and this weekend i've beenwatching art workshop videos from the library and thought i'd share clarifcation.

A: Water based
              1.  Transparent (mistakes will show so you have to use them)- watercolour,
Watercolour - is the only true transparent medium (ie you always get some light reflected from the white paper behind), though the white watercolour (except one which is semi transparent) is fully opaque so if you mix any watercolour with white you lose the transparency which would negate the main reson for watercolour. Transparency is good  to give a dazzling vibrancy, that is if you don't put on the watercolour too darkly(not enough water)  and if you leave some of the paper white as hightlights.   If you lose these highlights then you need to add some white at the end to bring the highlights back. (watercolour white would't be enough usually so you would use gouche or acrylic white because they are strong and opaque enough to cover any dark watercolours.)  In watercolour you work from light to dark - ie go in lightly and build up layers for darker colours.  - ie You can't add light colours over dark colours as they won't be visible enough.    You can also mix colours on the paper - put light wash of yellow, let it dry then a very light wash of red and you'll get more orange colour though this can be more difficult to get right. 


              2.   Opaque is good because you can always cover mistakes of any colour whether dark or light with another layer of paint of any colour dark or light- gouache, and acrylic are both water based opaque meidums,  though if you water them down enough you will a little transparency but not as much as watercolour.  I have some books thought that talk about using watercolour vibrantly and boldly so it's up to you what u do with it.  With opaque mediums for example you could paint a black box, then add white on top for a highlight.   You couldn't do this with watercolour.  with watercolour you would leave the paper white where you want the highlight and use the white of the paper as the highlight (you can get masking fluid to paint on this to avoid paint getting on it - the fluid dries to a rubber which you can peel off when u have finished the painting to reveal the white.   then you paint the black box, peel of the fluid and you have black box with white highlight.   if you lost this highlight - say not using the masking fluid and accidently getting the black where the highlight should be, then you would need to use white gouche or acrylic to get it back.

Gouchace  - opaque - used by graphic artists becuase of strong beautifully bright colour  - many artists coloured  felt tip pens are a form of gouche.  Also used with watercolour when mistake needs covering and you don't mind losing the transparency

Acrylic     - opaque, can be watered down for transparency.  can add lots of diff kinds of mediums to it to give texture amd make thicker like oil paint but it is usually matter finish than oil.  Is probably the easiest to handle and usually the cheapest.  Main prob is that it dries within minutes which stops you from blending on the page for say sublte colour changes in skin on different areas of face, that is if you really want very smooth skin tone - then oil would be easier, rather than a more impressionist brush stroke skin look which acrylic could handle.  You can use spray water bottle to keep them wet but if it dries you can't re-wet as it dries to a plasticy skin.   There is now a slower drying one just developed which supposedly you can wet even after it dries - i am going to buy one tube to try it.



B: Oil based
         - oil paint opaque, it's not so much the paint smells,  its the linseed oil which you use to thin the colour (gives more shine that spirits(  and the spirits you use to thin the colour (more quick drying that linseed oil) and used to clean brushes.  though you can now get a wonderful orange zest called Zest it   to clean brushes.  Oil paint takes long time to dry (decades for some thick old paintings) which is why you dont put glass on it when framed).  Because of this you have plenty of time to get the most subtle blendings of colours.  Usually good to work on several at same time so you can work on one while other is drying you enough to add next layer.   You can thin oil paint right down so it becomes almost transparent like watercolour and build up  a work using many many layers - this is called glazing and gives great depth.  Or you can use it as thick as butter for texture.    It led the art field because of it's sublety and beautiful butter look.  some artists think it's the top/only real art medium.  It gave the masters of renaissance when it was introduced, the power to do amazing portraits etc. 


Pastels are considered a painting medium because they can be blended on the paper to form new colours, you can even spray with a special fluid for more blending.  I've definately seen pastel works that i thought were painted.  It's messy but beautiful.

Hope this helps rather than confuse - it is just my understanding of course - i may be wrong/short sighted at this point.