Sketching tips for gouache paint

All three colours gouache, watercolour and acrylics are water soluble. However gouache colour is the only one which remains water-soluble all the time. Watercolour and acrylics dry to a permanent colour film that cannot be changed after drying anymore.
This can be seen as a disadvantage of gouache, but also as an advantage especially if wet in wet techniques are wanted.

Gouache colours are opaque as acrylics are, whereas water colours are transparent. Nevertheless Gouache colours can be thinned to a consistency that allows transparent colour layers too. The opacity of the gouache colours allows to paint over existing colour layers. Therefore it is much easier to paint landscapes in gouache colours than in water colours as the foreground of a gouache painting can be added on top of a background. This is of particular advantage when light parts have to be added to a painting later in the process. In water colours the lightest parts have to be kept free of colours from beginning to the end. This requires advanced skills in watercolour handling and for that reason many watercolour artists use masking liquid in order to protect the highlights in their paintings from unintended colour spots.

Gouache colour dries at a similar rate as watercolour. Acrylic colours dry faster then both. Under moist weather conditions when gouache colours dry slowly great wet in wet techniques and effects are possible. Wet gouache colours flow slower than water colours, this wet in wet effects can be controlled much easier than in watercolours.

All three colours can be mixed with each other. Combinations of watercolour and gouache go together well. Combinations with acrylics are more difficult as acrylic colours have a different look than the other two. Acrylic usually dries to a shiny film whereas gouache colours are always matte after drying.

I would describe gouache colours as soft or mild compared to acrylics which are often too aggressive or strong in colour for my personal taste.

art print Blooming trees
by editionha
See more Pink Posters

As with all colours one can say the more expensive a colour is the better it is. Better means in this case that the colours with high price contain a higher quantity of pigments and more durable pigments. More expensive gouache colours are suitable for long time exposure as wall decor for example.

The colours in the gouache set that I use for my sketchbook projects are sold as lightfast, but I understand that not all colours in the set are of same light fastness. It is well known that red and magenta pigments are less lightfast than others. Also I learned that the ultramarine blue and malachite green can change over time.

Therefore commend to use an artist quality of gouache colours for works that are made for sale or permanent display. Also it is more economic to use expensive colours. as these colors come with a high pigment load one need much less colour quantities.

Most producers of gouache colours offer products in different price ranges. The lowest quality is for schooling purposes, the next higher level often is called "studio" ,which is a mid range quality. The expensive qualities are associated with terms like "artist" or "designer" gouache (Schmincke terminology). So when you compare different brands one should keep in mind that a comparison between studio line and artist quality is problematic...unless you can get an artist gouache at the price of a studio quality!

Wet in Wet techniques means that a second colour is added to a still wet often very liquid layer of colour. With this process wonderful colour effects can be achieved. This technique is very popular with water colours. I discovered the beauty of this technique by incident when I tried to sketch while it was raining. I still do not like heavy rain of course, but a nice drizzling rain is an extra motivation for me to go out with gouache colours as there are many surprising colour effects, particularly colour transition possible when the paint is kept wet.

I think that it is not necessary to use a varnish for gouache paintings as long as a high quality colour us used.
However it may happen that you have done a nice piece with a studio quality colour and you want to protect it against UV light which causes the fading. In that case one can use one of the fixative sprays that are offered for that purpose.

I have experimented with a water-soluble liquid varnish that is normally used for acrylic colours. Of course this varnish cannot be applied directly on dry gouache colour as the liquid will solve the gouache colour and any brush movement whilst applying the varnish will smear the painting. Therefore I first put a layer of varnish spray on the dry gouache colour. After that the surface is not sensitive for water anymore, in fact most of the varnish spray a nothing but silicone sprays that are also used to protect shoes.
On top of the varnish spray it is possible to put down a layer of acrylic varnish too. The varnish I use gives a nice glaze to the
gouache colour and makes it look a bit like an acrylic colour.

Before such an experiment is undertaken I recommend testing the procedure first to avoid damage to your valuable work.

There are many ways to create structures with gouache colours. Here are some basic tips. On the sketch to the right I have used the handle of the brush to draw into the wet top layer of colour. Before I had lifted some colour off the half dried paper with a cotton towel from. Gouache painting can be worked over many times if you want by adding and removing colour again and again.

Scratching with a tool: hard brushes, brush handle, knife, stick,
Using cloth or tissue paper:dab with a tissue to remove excess liquid and colour, lift off colour with a cut piece of paper from a certain image area
Dry brush: Apply colour without dabbing the brush into water before picking up the moist colour from your palette. Bristle brushes will create parallel lines which are great to paint tree bark for example.
Lift off with adhesive tape: Put adhesive tape on the moist or dried colour. Lift off the tape to remove colour, do not press the tape too hard in order to avoid damages to the paper.

There is a magnificent gouache color which is not very well known in the art and illustration community I believe.
Kt- Color produces two sets of fine gouache colours with very special colours and hues.

This silica based colours are very durable and lightfast, they were originally developed for outdoor use.
If you are interested in a high quality colour set that will give your work a unique colour style I commend to have a look at :
KT-Color Poly Chrome LeCorbusier