“Your print has been Schweidlerized” Tuesday, Mar 17 2009 

Max Schweidler - The Restoration of Engravings, Drawings etc.

Picture yourself having just acquired an old master print (say, a Rembrandt etching) at an auction. The print is in a exceptional good state, and you bought it at a reasonable price (“reasonable” meaning in reasonable relation to the size of your wallet, of course). After the auction, this well known old print conaisseur which you watched lingering around the specimens shown at the pre-sale exhibition approaches you and tells you with that calm voice expressing a life full of old master print expertise: “Madam/Sir, I have to to tell you: your print has been Schweidlerized“.

Schweidlerized? What does he mean?

  1. The print is a fake (“swindle”)
  2. The print has been skillfully repaired, virtually invisible to the eye, or
  3. The print was sold (at an auction etc.) at a much higher price than what it is actually worth.

Read on for the solution and the rediscovery of a tremendously valuable book.


Thermal photography identifies watermarks in old prints Sunday, Oct 14 2007 

When you hold an old print or drawing in front of a light source, you can often discern an image or pattern within the paper itself – a watermark. They play an important role in identifying fakes and dating old master prints. Sometimes the writing or drawing is so dense that it renders it difficult to identify the watermark under normal light. Now a scientific team in Germany has developed a new method for identifying even poorly discernible watermarks.

The physicist Peter Meinlschmidt at the Fraunhofer-Institute for Wood Research in Germany developed a quite simple, but effective thermographic method to make watermarks clearly visible. He uses the fact that printed ink is transparent under thermal radiation. A thermal source is placed behind the drawing or print; a digital camera which is sensitive to thermal radiation shows the watermark density differences in the paper. As an example, under “normal”, visible light, the watermark in the drawing by Jan Lieven is barely visible (left). A thermal infrared picture of the same drawing shows clearly a crown watermark (right).

Jan Lieven Drawing - Watermark

Pictures from http://www.wki.fraunhofer.de/projekte/wki-pmt-2.html


Original oder Fälschung? (in German)

The Crazy Sheep Project has come true Wednesday, Mar 14 2007 

Two years ago, Michael Drout over at his Wormtalk and Slugspeak blog got all excited with the idea to extract DNA from old parchment. Nicknamed the “Crazy Sheep DNA Guy” at this time, his dream has now come true, at least to a certain extent.

ParchmakerParchment is made of animal skin, mostly from goat and sheep, which has been dried and scraped under tension. It was the preferred writing support material for manuscripts and maps from around 200 BC until the 16th century, when it was replaced by paper. In the late Middle Ages, town parchment makers (“parchmenters”) had shops in the vicinity of artisans and trade groups. The picture to the left shows a German parchmenter around 1568 [1].

Parchment was much more expensive than paper, and as such still used later on for high-grade books and prints, notably by etchers in th 17th century (and here we have the link to Oldprints).