THE CARE OF PICTURES AND PRINTS. 89 



on the " Fugacity of Colors." Here is Field's caution on the subject, 

 which deserves attention : 



" Others, with some reason, have imagined that when pigments are 

 locked up in varnishes and oils they are safe from all possibility of 

 change ; and there would be much more truth in this position if we 

 had an impenetrable varnish and even then it would not hold with 

 respect to the action of light, however well it might exclude the in- 

 fluences of air and moisture ; but, in truth, varnishes and oils them- 

 selves yield to changes of temperature, to the action of a humid 

 atmosphere, and to other chemical influences : their protection of color 

 from change is, therefore, far from perfect." 



The best way, then, to keep oil-pictures in a state of safety is not 

 to trust much to their power of resisting damp, but to treat them just 

 as if they were notoriously delicate things like water-color drawings, 

 although in reality we know that their constitution is more robust. 

 An oil-picture, it is well to remember, may be attacked by damp from 

 behind. If it is hung on a damp wall, the canvas will absorb damp 

 from the wall, like the mill-board behind a water-color, and this damp 

 will reach the colors through the priming. The proof that canvases 

 absorb damp is that they hang flaccid on their stretching-frames when 

 there is much moisture in the atmosphere. It is some protection to 

 have the back of the canvas protected by a coat of paint applied with 

 varnish, but a still better protection is to have two canvases on the 

 same stretching-frame, the one that bears the work of the painter and 

 another behind it with a coat of paint on both sides. The practice of 

 having two canvases on the same stretcher has been adopted by more 

 than one modern painter for various reasons. One reason is that an 

 accidental blow to the canvas from behind,* or an indentation from 

 some angular object, may produce a fracture of the paint in the pict- 

 ure a fracture not immediately visible, perhaps, but likely to show 

 itself later. 



It is generally of no use to propose anything that has not been 

 already adopted to some extent in practice, but I may call attention 

 to a plan which is successfully adopted by house-painters to protect 

 wall-papers from damp. Their way (or one of their ways) is first to 

 apply tin-foil to the wall, making it adhere by means of a thick coat 

 of white-lead. This is found to be a good protection for the wall- 

 paper which is pasted on the tin-foil. It would probably, in the same 

 way, be an excellent protection for pictures if the double-canvas sys- 

 tem were adopted and the under canvas covered with tin-foil upon 



* Canvases are exposed to injuries of this nature in exhibitions chiefly, from the 

 corners of other pictures that may be carelessly placed against them, before or after the 

 exhibition. In private houses this danger is scarcely to be dreaded, but it is well to 

 bear in mind that all people except painters believe that it does no harm to a canvas to 

 lean it against the corner of a chair, a table, a box, or anything that may present itself 

 conveniently. 



