Digital BW, The Print

Paul;

Anyone that's been at this for a few years remembers the odd 
exagerated Epson claim, or Wilhelm having to redesign his methodology 
to account for reciprocity. So in absolute terms you're probably 
right, many of these claims might indeed be rubbish, but they give us 
some kind of approximate reference. As Paul Roark mentioned, we also 
like to add our own side-by-side comparisons with known materials to 
get a better idea. 

While I've heard of the BWS test standards I don't know enough about 
them to have even the foggiest what a BWS of 7 means. So a little web 
research produced the following:

Blue Wool Test. Most lightfastness tests expose paint samples to 
abnormally intense light radiation, because this more quickly 
produces fading or discoloration in impermanent paints. Thus, samples 
of artist's pigments may be tested by exposure to direct sunlight, 
even though paintings are normally displayed under much weaker indoor 
lighting. (Thanks to low latitude sunlight intensity and largely 
cloudless climate, it is generally accepted that the most rigorous 
outdoor pigment testing is done at commercial sites in Florida or 
Arizona, USA.) 

How much light exposure are we talking about? Direct outdoor sunlight 
or indirect sunlight in a bright room yields anywhere from 5,000 to 
100,000 lux of illumination. This can produce a cumulative radiance 
exposure (depending on weather) of up to 25 megalux hours annually, 
which is 30 to 50 times higher than the brightest art gallery 
illumination.
 
  
 The problem then is to measure the amount of light exposure the test 
samples receive. The current solution is the blue wool textile fading 
card or blue wool scale (at right). This consists of eight strips of 
wool mounted side by side on a small card; each strip or reference is 
colored with a blue dye that fades after exposure to a known amount 
of light. The dyes have been chosen so that each reference takes 
about two to three times longer to begin fading as the next lower 
reference in the scale. (Under normal solar testing conditions, 
reference 1, the least permanent, will begin to fade in 3 hours to 3 
days, depending on geographic location, season, cloud cover and 
humidity; reference 3 will fade in 5 days to 2 weeks; reference 6 in 
6 to 16 weeks; and reference 8, the most permanent, in 6 to 15 
months.) These scales are used for paint lightfastness testing under 
international standard ISO 105-B, and are also used by gallery 
curators to measure the accumulated amount of light received by 
museum displays of paintings, textiles or photographic prints.  

And from the  Fine Art Trade Guild website: 
'Recent tests show that the resulting print can be lightfast to very 
high levels with a minimum of six on the Blue Wool test, or 25 years 
by Wilhelm Institute tests.'

Interesting.

Steve Karafyllakis

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "failedthespian" 
<failedthespian@...> wrote:
>
> Steve and Paul
> 
> Our inks are tested to an internationally accepted standard; the 
Blue
> Wool Scale (BWS).  This is an internationally accepted ISO standard 
that
> has been in existence for over eighty years; whereas the Wilhelm 
test
> has not.  The BWS test is in use by the worlds' most respected
> institutions - whereas the Wilhelm test is not.
> 
> The BWS does not predict fade properties in terms of years.  Most
> informed students will understand that due to reciprocity failure 
it is
> disingenuous to claim that a particular ink will have a fade free 
life
> of a certain number of years.  And yet organisations like Wilhelm
> continue to churn out figures conferring that this ink or that ink 
has a
> life expectancy of X.  This is rubbish!
> 
> We know that certain inks that have been accredited with having a 
life
> of seventy years, and yet the magenta and light magenta components 
of
> these ink sets failed to get past BWS2.  This is a truly dreadful 
state
> of affairs.
> 
> The Fine Art Trade Guild sets a minimum standard of BWS6 for all 
inks
> that are to be used for prints intended to be displayed.  We know 
from
> our own BWS testing that a considerable number of so 
called "archival"
> inks accredited by Wilhelm would fail this basic test.
> 
> I trust this answers your point.
> 
> Paul Banks
> Image Alchemy Ltd
> 
>