Re: Gum problem(s)

From: Tom Sobota ^lt;>
Date: 11/18/05-06:54:03 PM Z
Message-id: <>

Yes, by all means test it for yourself. However please keep in mind that
this was only said and meant as advice for a beginner.

Beginners, and I was no exception so I know, mostly tend to coat too
heavily. In this context, the "newspaper test" is useful, I think.

"Who says" you ask. To tell you the truth I don't remember. I read it in
a couple of different places years back. When I find it again I will tell you.
Anyway it has been useful for me in a time long before Internet, when
there was nobody to ask.

What is important is perhaps not this test but the fact that the coat should
be rather thin and keep a certain transparency at all times. This fact is well
attested in the bibliography:

"If the coating appears to be dark enough to completely hide the paper
from view, then it's either too thick or too much pigment has been used."
("Historic Photographic Processes" , Richard Farber, 1998)

"The paper is covered with a thin coat of this mixture, so that the paper
can still be seen through the color..."
("Manuale prattico e ricettario di fotografia, Rodolfo Namias, 1914)

"Dieselbe (die Mischung) muss so dünn aufgestrichen werden, dass
das Papier noch durchscheint..."
("Das Pigmentverfahren, der Gummi-, Öl- und Bromöldruck und
verwandte photographische Kopierverfahren mit Chromsalzen"
Josef Maria Eder, 1917)

and many others. The "newspaper test" is only a simple method to
check the transparency of the coat before applying it.

But I think that it was originally meant for checking the dark colours
usually used for one coat printing. The transparent colours used for
trichromy are ... well ... transparent.


At 21:53 18/11/2005, you wrote:
>Second thought:
>I sent something through a while ago, questioning the advice about coating
>so that you could read text through the coating. That post hasn't found
>its way back here yet, but I've been thinking more about what I said, and
>decided I don't necessarily agree with myself. After all, I've always
>been a great one for printing with transparent pigments, and no doubt you
>can see the previous print through subsequent coatings on a tricolor
>print, even (very dimly) the cyan layer which for me goes on last. Even a
>very dark color that's transparent, say ivory black, is transparent
>enough that I wouldn't be surprised if you could read a newspaper through
>it, even though it can print as dark a value as lamp black can.
>In my previous comment, I was think not of transparent layers but of a
>coating intended to produce a one-coat print, like lamp black or a
>blue-black or brown-black that you might use for this purpose, and I still
>wonder about that, but like I said, I'd have to try it for myself.
Received on Fri Nov 18 18:54:43 2005

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