RE: Infrared Detection of Paint Layers

[Jason Revell <jason.revell@xxxxxxxxx>]

	>>I'm interested in using
> >>infrared film for paint investigations.  Specifically, can infrared film
> >>detect paint patterns under a layer or under several layers of old
> paint?
	>>Do know where I could get some information on this type of
research?

I have just come back from holiday so sorry, this reply to this thread is a
little late. (Clive if you would like to pass my details onto Jeff I will
help him with any information/techniques he needs).


	>There is information in Clark about this. Basically, infrared can 
	>sometimes penetrate the canvas (or vellum) on which the painting is

	>made so you see the deepest paint layers from behind and sometimes 
	>the pigments themselves.

The only Time I have ever had any success with IR on a work of art on Canvas
when viewed with IR from behind is if the painting has been relined (stuck
on another piece of canvas) and the method used for the relining has been
wax.  This used to be a very common method but is now not realy used.  As
the wax penitrates throught the whole canvas layers it can become possible
to view the previous canvas with IR, getting a inscrition to show may be but
not normaly any of painting it's self.  Paper and vellums are of course a
different matter and you can have more success with them but it will bepend
on how think they are (you will need to be very thin).

The reason why viewing from behind will not usualy work on a canvas painting
is;

Most paintings (depends on the artist usually) have a 'ground' layer that
act's as a 'key' for the canvas and paint layers, so the paint has a smooth
and stable base to sit on.  This ground layer in nearly all cases reflects
IR (I have never come across one that does not yet, though I don't want to
say they all do!).

So if you view from behind and can get some IR penitration of the canvas the
IR light will then hit the ground layer and reflect straight back, showing
nothing but the blank ground layer.

However if viewed from the front the ground layer helps, as any penitration
on the pigment's used will reflected back by the ground layer, showing as a
lighter tone or even white.  Also artist's quite often draw a sketch on the
ground layer before starting the painting so this would normaly give us IR
reflective ground with IR absorent carbon (charcoal, pencil ect.,) and as
such we can sometimes see the underdrawings as well and alterations the
artist has made before or even during painting.

	>There is an example set of images in the book with references to
work 
	>at Harvard University, Pennsylvania Museum of Art and the 
	>Metropolitan Museum of Art in NY. This work was all done prior to 
	>1946.
	>
	>There is an extensive bibliography on this particular subject and I

	>could fax this or send a scan if you're interested.
	>
	>[Clark, W - Photography by Infrared (2/e): Chapman Hall 1946]

I am intrested in this article, is their any chance of a copy?
	>
	>Andy Finney
	>www.invisiblelight.co.uk

Jason Revell
Photographic Technician
Conservation of Fine Art
University of Northumbria

	jason.revell@xxxxxxxxx
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