RE: glyoxal yellowing now: How do you know it's hard?

From: Don Bryant ^lt;[email protected]>
Date: 02/04/05-05:40:10 PM Z
Message-id: <200502042340.j14Ne7eM003356@spamf2.usask.ca>

Katherine,

> That was so gritty you could have taken paint off
> with it if you'd used it for sandpaper, and it snagged my skin when I
> ran my fingertips across it. But this is smooth on glass, as I said, and
> on the Artistico Extra-White it is slightly rougher than the fresh paper
> out of the box, but so is the same paper after it's been soaked without
> sizing; I can't tell the difference between the two.
>

It has been my experience with Rives BFK that hardening with glyoxal (15 ml
of 40% gly per liter of 4% gelatin) produced a rough, not soft, surface.
Also note that the paper was rinsed after sizing while still wet.

> So here's my question: does anyone have any knowledge of
> gum-printed glyoxal-hardened gelatin turning yellow later, or is this
> purely a phenomenon that occurs when people size paper and then leave
> it for a period of time before printing it?

It's my impression that the yellowing begins as soon as the sized paper is
dried but may continue to yellow over time. My conclusion is that glyoxal
hardened gelatin will yellow paper when not rinsed or will yellow the paper
if the gelatin thickens while drying such as on the corners or edges.

Now my question is does the yellowing ever occur when the gelatin is
hardened with formaldehyde or formalin?

Also to what degree do gelatin sized papers need to be hardened?

Don Bryant
Received on Fri Feb 4 17:42:59 2005

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