Re: gum dot test - Crawford

Good catch on the tube diameter John.

The only way this test will have any practical relevance is if you
define the parameters yourself based on the materials you will be using.
 Pigment strengths, weights, fillers, particle surface area, gum
quality, paper and sizing choice, humidity, the alignment of the
heavens, etc., are all going to vary and affect your personal results.
(Oh, and after I've finished, don't believe anything else you read on
this subject here.)

I would strongly suggest that if you wish to do this test and believe it
may give any practical data (doubtful IMO), that the very least you
should do is mix the gum plus pigment with the dichromate sensitizer
since that will affect the dilution, viscosity, drying time and staining
potential of your actual printing mix. Otherwise you are doing apples
and oranges.

You'll find opinions shall we say vary considerably about the usefulness
of Crawford's/Skopick's/Andersen's gum-pigment ratio test. Check the
list archives for more.

Joe

>>> john@glossyormatt.com 08/03/05 7:23 PM >>>
Hello list

I'm about to do the dot test en masse as on page 211 in Keepers of the
Light. Watercolour pigment is given in length of 3.8cm or 1 1/2" but
there is no mention of tube weight. Pigments I want too test range from
5ml (0.17 US fl oz) to 37ml (1.25 US fl oz) and the exit holes of the
tubes vary in diameter, so a 3.8cm length doesn't mean much. Can anyone
enlighten me on either the tube weight Crawford used or give me a sample
weight as a starting point.

Many thanks

John.
Received on Fri Aug 5 12:36:34 2005