Re: Gum Arabic Solution

Date view Thread view Subject view Author view

From: Judy Seigel (jseigel@panix.com)
Date: 02/18/01-05:19:19 PM Z


On Sat, 17 Feb 2001, Dave Rose wrote:

> Could you elaborate on that a bit? Are there certain circumstances in which
> diluted gum is advantageous? (I always use gum 'straight', out of the jug).

Dave, the "best" viscosity of a gum coat probably depends on the paper,
the size, the amount of pigment, and ratio of gum to sensitizer.

Some people use 1 part gum to 2 parts sensitizer... which would make a
thinner mix than my usual 1 to 1 -- but also uses more dichromate. In a
sense my added water is like that proportion with a half-strength
sensitizer -- EXCEPT I don't necessarily stick to equal parts gum &
water... I usually brush a bit out & add by feel.

The point is that if the emulsion is too *sticky* it doesn't coat evenly,
starts to get dry & gummy on paper before it's smoothed. And I also find
that the tolerance for *thin* coat is pretty wide. Maybe after coat #1 the
paper is tanned (?) but I don't recall ever getting pigment stain from too
thin emulsion. (Of course it's possible I have a kind of overall tone &
don't notice or care about "stain.")

But you can also see that adding water depends on how much, how thick the
tube paint, probably a whole other thing with your dry pigments.

Hope this makes sense... But remember the *context* was that generally
speaking exact baume of the gum isn't a problem. 14 is not (around here)
magic number, but more a guide to getting a *regular* lithographer's gum.

Judy

>
> Best regards,
> Dave Rose AKA Cactus Cowboy
> Big Wonderful Wyoming
>
> Judy Seigel wrote:
>
> (snip)
> > If it's not 14 degree baume doesn't matter either. That's just a starting
> > point: I add water to a mix about 99% of the time. Viscosity and
> > proportion of gum emulsion aren't cast in concrete, in fact best changed
> > according to needs of each color and layer, I find, usually.
>
>


Date view Thread view Subject view Author view

This archive was generated by hypermail 2b30 : 03/06/01-04:55:39 PM Z CST