Re: "speckling" v "staining " (was New Orleans/glut)

On Sun, 4 Sep 2005, Katharine Thayer wrote:

> This same kind of speckling can be caused by sizing with the size too
> hot, and by the same token I think it depends on the paper whether this
> is the case or not. There was a time when I thought that it was
> something about getting the gelatin too hot that caused the speckling,
> but later I came to realize that it didn't have anything to do with the
> gelatin;, it's just about the water that the gelatin is mixed into,
> being too hot.

If the gelatin is mixed into water that's too hot, we can't say for sure
whether it's the hot water alone, or the gelatin in the hot water that
causes whatever. I've had spekling from gelatin overheated itself or
sprayed with overheated water, but never from hot water alone in
shrinking.

I proved this to myself once when I was sizing papers and
> reheated the size in the microwave (I think Chris's thermos idea for
> keeping the size at the correct temperature is excellent) and realized
> after sizing a few more papers that the thermometer had gone up to 160F.
> I marked the papers that had been sized with the hot size, and cooled
> the sizing down to 125 or so before finishing the sizing. Sure enough,
> the papers that had been sized at 160 speckled when printed with gum,
> but the papers that were sized after the gelatin was cooled, didn't
> speckle. So obviously it didn't have anything to do with anything that
> happened to the gelatin, but only with the interaction between hot water
> and the internal sizing of the paper. I'm sure I reported this to the
> group at the time.

As noted, I've shrunk paper at near boiling temperatures and not gotten
speckling. With faulty size of various sorts for various reasons, got
speckling. If gelatin is in 160 degree water, that's by no means proved to
be the same as 160 degree water alone.

Judy
Received on Mon Sep 5 21:27:25 2005