RE: Copy of: Re: Copy of: Re: Copy of: buying Gum Arabic
>I wrote
The sensitised gum is dried in the dark and then
> exposed for two or three minutes, and then washed to remove the traces of
> Dichromate, before the first coat of pigment is applied. I did think of a name
> for this method.
> The method works well for hot pressed papers.<
> Peter replied
>
> Yes I can confirm that this method does work well, however there can be a
> few problems associated with its use. The exposure required to set the
> layer is very brief and critical, I have test run this method at Kingsway
> college KTC, we use a sunbed as an exposure unit, which gives us an
> exposure of 3 to 10 mins when printing an average gloy gum print, using a
> standard mix of 1 part , distilled water, 1part,saturated solution amm
> Dichromate ,and one part gloy gum. With one part pigment to 10 parts
> standard mix.
>.You just use the gum or gloy mixed with 50/50 with the saturated dichromate. I
am surprised you put water with it Peter. Shove it under until you perceive a
change in colour and whip it out, about a minute. We can manage 0.1 of a second
exposures under the enlarger, what is so difficult about 1 minute under my lamp
or 15 secs ( ? ) under yours ?<
Dear Terry
I use a more dilute gum mix than you out of personal experience, I find
that the 50/50 mix a bit to thick for my personal tastes, and the fact that
I worked for years on a plastic substrate the 50/50 mix plus pigment
tended to flake of after ten coats as the physical thickness was just to
much and the extra viscosity of the mix did not help, I am sure if I had
been working on paper this would not have proved a problem but other
factors such as pigment stain would, for the type of polychrome work I was
attempting. However this does not mean I should stick at this mix now that
I am working in monochrome on paper it is just that old habits die hard. I
would like to make a nun joke here but I know you will have none of it ;-)
Honest I am making no difficulty between your exposures and mine, I think
I'm going to have enough troubles on my hands in the near future without
starting a storm in a teacup, the only thing I am going to say is that the
initial exposure is a bit critical if you wish to have a print free of
dichromate stain. Your suggestion of using the enlarger instead of the
sunbed is brilliant, thanks for the tip.
pete