Digital BW, The Print

In addition to the stability of the inks, storage conditions, etc., the
acidity of the photo paper is considered an important factor in the
longevity of ink jet prints.  With a pH testing pen it is easy to get a
qualitative reading of paper acidity: the color of a little swipe on the
paper is blue if the paper is acid free, green if there is some acid
content, and yellow for high acid content.

I tested a number of papers (kindly supplied by TK Thompson) from Epson,
Hahnemuhle, Hawk Mountain, Innova, and Moab, and found that the interior or
core of the papers to be acid free, with one exception.  (The coating, on
the front or back of the paper, has to be removed to reach the core.)  Here
are the results, where b = blue, g = green, and y = yellow. The colors
after a paper's name refer to front, core, and back, in that order.
(E-mail does not allow tables, unfortunately.)

Epson papers
Premium Glossy, g, b, (g)
Premium Lustre, g, b, (b)
Premium Semigloss, g, b, (b)
Ultrasmooth Fine Art, b, b, b
Velvet Fine Art, b, b, b
Enhanced Matte, b, y, y
Colors in parentheses mean there was very little penetration because of the
coating.

Hahnemuhle
Photo Rag Bright White 310gsm, Photo Rag Duo 316gsm, Photo Rag Satin
310gsm, German Etching 310gsm, William Turner 310gsm, Museum Etching
350gsm, and Photo Rag 308gsm. All are b, b, b, except Rag Bright White
which is g on the back.

Hawk Mountain
Sharpwing Glossy, Broadwing 10SG, Broadwing  8SSG, Sharpwing Lustre,
Grayhawk 2 Brite White, Grayhawk 1 Photo, Condor Britewhite, Merlin
Britewhite, Merlin 2 Natural, Peregrine Velvet 250, Merlin Photo Textured,
and Merlin Photo. All are b, b, b, except Sharpwing Glossy which is g on
the front.

Innova
F Gloss Ultra Smooth, Photo FibaPrint Ultra Smooth, Soft Textured Art,
Photo Smooth Cotton, and Cold Press Art. All are b, b, b, except for F
Gloss Ultra Smooth which is g on both the front and back.

Moab
Keyenta Photo Matte, Entrada Fine Art 190gsm, Entrada Fine Art Natural
190gsm, Kokopelli Photo Satin 235gsm, Kokopelli Studio Semi Gloss 285gsm,
and Kokopelli Photo Gloss 260gsm.  All are b, b, b, except Photo Satin and
Photo Gloss which are (g) on the back.

  Anyone interested can get a pH pen (from Light Impressions, for example)
and test new papers as they are introduced.  However, with the exception of
Epson Enhanced Matte, photo paper acidity doesn't seem to be a problem, and
one might hope that exception would be fixed soon.

   Loren