Protecting a Gouache painting
Your technique may have led to what is known as dusting off, where the surface of the painting looks dusty, but once again varnishing will not help. Dusting off occurs when the colour has been diluted with too much water, leaving only pigment on the surface and an underbound painting. The solution is to avoid this happening in the first place and to add gum Arabic when preparing your colours.
However, this does not mean gouache paintings need to be left unprotected. Framing the work behind glass will help. Remember to put a small distance between the glass and the work itself – paintings placed directly against glass are prone to condensation and the growth of mould. A mount between the paper and glass allows just enough circulation to prevent this.
To help your work last over time it is recommended that you follow the permanence ratings of the colours you are using. This can be found on each of the colour pages of Designers Gouache on this website. See below for a short overview of these:
• AA and A: Colours with an AA or A rating are not expected to fade, such as Brilliant Yellow and Sky Blue.
• B and C: Colours with a B or C rating tend to fade over a 10 year period, such as Light Purple (B) and Parma Violet (C).
• Fugitive: Some colours within the C band are known as Fugitive which means transient and these may fade within months.