Quotation

How to Cleanse an Old Painting, so as to preserve the Colours ; with cautions to those that through ignorance have in stead of Cleansing, quite Defaced or irrecoverably lost the Beauty of good colours in an Old piece of Painting.

To Cleanse any very old Picture in Oyl.
Take your purest white Wood-ashes you can get, and sift them very well in a fine lawn sieve ; or else some Smalt, which is as some call it Powder blew, and with a fine Spunge and fair water wash the Picture you intend gently over, but be sure you have a great care of the Shadows ; for by the ignorance of many persons many good Picture hath been abused ; but having carefully wash’d it, as before mentioned, take some of these Vernishes, of which there be several, but some are more prejudicial than others, therefore chuse those which may upon occasion be wash’d off again
As Gum-water purely strain’d, or pure Size-gelly, or the whites of Eggs well beaten ; all these will wash off.
Your common Vernish will vernish over any very dark part of a Picture.
But your distill’d Vernish is the best of all ; this will not wash off.
But observe, that when you have wash’d the Picture, you must dry it very well with a clean cloth very dry before you varnish it.
Divers there be which have pretended to be well skill’d or knowing in the Cleansing of Pictures, and skill in Painting ; and have undertaken the spoyling of things they have been unworthy to understand ; as with Sope, or Ashes, and a Brush, and divers other inventions, by their ignorance to deface and spoyl those things which otherwise might have been worth great value, and in stead of hindering the Painter of his employment, have indeed created them new work.

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