It is difficult to retouch/inpaint paint losses on the painting painted on absorbent surfaces i.e. cardboard, painting boards and similar. Solvent and medium are absorbed and discolour the support making proper assessment of colour matching impossible until the solvent evaporates. The same problems occur when retouching matt, absorbent paint, tempera or gouache. Retouching medium and pigment are absorbed and migrate into the surrounding paint causing permanent discolouration and drying rings.

B72 Retouching Gels retain solvent and resin within their liquid crystal structure and therefore the undesirable migration and discoloration of absorbent support and/or matt absorbent paint is avoided.

Fast - Hard 25 Si, Fast - Heavy 20 and Fast - Light 10 Si B72 Retouching Gels are recommended for painting on absorbent supports.

Below are the photographs and macrophotographs of the tests that were carried out by painting with different media on very absorbent paper kitchen towel.

• ‘D’ was painted with rich in pigment paint made with a diluted solution of Paraloid B72 such as one would make for retouching a matt surface.
   
• ‘SO’ was painted with Paraloid B72 15% solution in 1-propoxy-2-propanol
   
• ‘LC’ was painted with liquid crystal Fast - Light 10 Si B72 Retouching Gel

The images show both sides of the paper towel in order to demonstrate the degree to which the medium and pigment migrate into the support. The reverse of the towel shows the depth to which each medium penetrated.

Close-up photographs

Results

‘D’ – Paint made with a diluted solution of Paraloid B72 was absorbed, spread and penetrated to the back of the towel. The medium spread even further leaving a halo of drying rings.

'SO' – Paint with 15% solution of Paraloid B72 migrated to a lesser degree. It bled into the support and lost definition of brushstrokes.

‘LC’ – Only Fast-Light 10 Si B72 Retouching Gel retained crisp definition of the letters on the front of the towel and did not migrate or bleed through to the back, despite  being less concentrated than 15% solution of Paraloid B72.

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