Applying varnish looks to me an other art , right temperature , right humidify , right thickness and density , even right phases of moon , they say effect the quality.
What can be wrong , varnish could be cracked in a short time or distort the paper , or heaviliy yellowing.
This is a huge deep technology and you have to get advise before diving in this stuff.
Where are these experts ?
www.wetcanvas.com is a good place , there are 250 000 members and 2 million posts.
What can renaissance varnish add to my photographs ?
they say it adds lumionosity
http://ambervarnish.com/index.php?pr=medium_stepbystep
Step-by-Step Instructions
The following copy of Sir Anthony Van Dyck's "Portrait of Cornelius Van Der Geest" as painted by the renowned American painter Joseph H. Sulkowski will serve as our example of how to apply several layers of wet paint in one sitting using our various mediums.
It is important to note while proceeding through the steps that the setting-up and drying times in a painting can vary depending on the absorbency of the canvas or panel grounds, as well as the atmospheric conditions and weather.
OUR MEDIUMS GO A LONG WAY: By adding our mediums to tube or dry colors on the palette with an eye-dropper, painters can attain great savings without sacrificing quality.
Materials used in example:
Mediums
Oil of Delft Painting and Grinding Medium
Oil of Delft Painting Medium Thin
Oil of Delft Painting Medium Thick
Optional (for increased luminosity, hardness of the paint film, and an unsurpassed sense of depth).
Amber Varnish Thick
Amber Varnish Thin
Paints
Yellow Ochre
Raw Umber
White Lead or Titanium
White
Cadmium Red Light
Neutral Gray (mixed)
Terra Verte
Terra Rosa
Alizarin Crimson
Ivory Black
Step One
First Joseph mixes enough Oil of Delft Painting and Grinding Medium with some yellow ochre tube paint* until he has achieved an ink-like solution.
Next he dips his round bristle brush into this thin mixture and proceeds to define the linear aspects of his underdrawing.
The semi-absorbent nature of his gesso ground enables this process to proceed much faster than if his ground were not absorbent.
*Dry pigment ground in oil could also be used where "tube paint" is indicated here and elsewhere.
Step Two
Joseph now allows about fifteen or twenty minutes for his yellow ochre underdrawing to set up.
When he feels a drag on his brush, he proceeds to mix some raw umber with Oil of Delft Painting and Grinding Medium into a thin ink-like solution.
With this color mixture he begins to mass in the large areas of shadow and also to reinforce the bone structure of the head.
Next he gently spreads his umber-saturated medium over the background establishing a transparent atmospheric tone.
Step Three
Next Joseph masks in the light areas of his portrait using the following colors: white lead or titanium white, yellow ochre, cadmium red light, and a premixed gray value oil color. Each of these oil colors has been prepared as the others by mixing into them small portions of the Oil of Delft Painting and Grinding Medium .
Once these colors have been mixed with the Medium, Joseph uses a mixture of white lead or titanium white oil color and yellow ochre to model the subject's forehead. He then mixes some cadmium red light and gray into the white lead and yellow ochre to refine the flesh tones.
Once these layers of wet tube color are mixed with the Medium so there is a drag on his brush, he mixed some cadmium red medium with some of the Oil of Delft Painting Medium Thin and gently glazes over the lips.
By mixing a small amount of light gray value oil color with some Oil of Delft Painting Medium Thin , he gently applies some small strokes of gray paint to the beard and hair on top of the transparent paint layers below. Here the painter will find that he is able to apply a second and third coat of paint, wet into wet, without disturbing the layers below, remembering periodically to judge the receptivity between coats by judging the drag of the paint under his brush.
Joseph now premixes several values of skin tones from light to middle to shadows on his palette and into each of these premixed tones he adds one part Oil of Delft Linseed Painting Medium Thick . (Thin may also be used if preferred; a small amount of Amber Varnish Thick or Thin can also be used instead.) With these colors he models the forms of the head including the eyes, nose, and mouth structures.
Step Four
After allowing thirty minutes to an hour to pass, Joseph uses a soft sable brush to pass a layer of Oil of Delft Painting Medium Thick over the surface of his painting.
*** For the painter interested in increased luminosity, hardness of the paint film, and an unsurpassed sense of depth, one can substitute a layer of our Amber Varnish Thick or Thin over his portrait at this stage of the painting.
With another fine sable brush, Joseph now picks up some flake white or titanium white oil paint (without mixing it with any medium) and begins to draw the fine lines of the beard, mustache, and the highlights of the eyes.
After he has worked up his painting from the midtones to the lights, he moves in the other direction and refines his portrait's transparent shadows using a mixture of raw umber, terra verte, and some terra rosa mixed with Oil of Delft Painting Medium Thick . (As above, Amber Varnish Linseed Thick or Thin may be used instead.)
Then he mixes some rose madder with some Oil of Delft Painting Medium Thick and glazes the cheek, the bone at the tip of the nose, and the upper and lower lips.
For finishing touches, Joseph reinforces his accents using touches of alizarin crimson and black mixed with a very small amount of Oil of Delft Painting Medium Thick to touch up the corners of the mouth, nostrils, and pupils of the eyes.
Note: To add depth, and to protect and preserve it, the painter can pass an ultra-thin coat of Amber Varnish Thin (walnut or linseed) over the painting with a fine sable or squirrel hair brush after the painting has thoroughly dried.
