Re: Gum hardening -- top down?

From: TERRYAKING@aol.com
Date: 04/06/06-10:02:39 AM Z
Message-id: <359.18d3699.3166959f@aol.com>

In a message dated 6/4/06 4:00:04 pm, dstevenbryant@mindspring.com writes:

> Terry,
>
> >
> and my own gum made from gum arabic powder to consistency of. again. 17
> Baume.
> >
>
> Okay I mix gum from powder. How does one determine the Baume of gum?
>
> Don Bryant
>
>

Don

When I started I had never heard of Baume so I mixed the gum to the same
consistency as the W&N stuff.

When I started photogravure I had to buy a Baume hydrometer to measure the
specific gravity of the
ferric chloride you use to etch the copper. It looks like a glass tube
thermometer but with lead shot in the bottom instead of mercury. You pour the liquid
to be measured into a narrow graduate and float the hydrometer in it. The
degrees Baume are etched on the side of the tube. The specific gravity in degrees
Baume shows where the surface of the liquid corresponds with the markings on
the side of the tube.

I bought mine from an art print supplier, Intaglio, in Southwark Bridge Road,
SE 1. Mine cost about five pounds.

My gum arabic without any preservative has kept for a year now in its nice
brown bottle but has increased in specific gravity from 17 to 20. I don't use
the gum arabic much as I bought rather a lot of Gloy last year. Now I wish I
hadn't now I know how easy it is to mix the stuff.

Terry

Terry King FRPS

RPS Historical Group (Chairman)

www.hands-on-pictures.com/

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Received on Thu Apr 6 10:05:16 2006

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