Re: Gum problem(s)

Tom,

I was replying to Judy but I assume anyone can put in is word and I don't
have a problem with that on the contrary.

----- Original Message -----
From: "Tom Sobota" <tsobota@teleline.es>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, November 18, 2005 11:13 AM
Subject: Re: Gum problem(s)

> Yves,
>
> I'm not Judy, but if you allow for an additional opinion ...
>
> In the first place, 11.5ml of mix seems to me way too much for covering
> a 5" x 7" sheet. Or you perhaps use this quantity for coating several
> sheets?

Yes, it's to much and worst it's wasted at this time.

>
> Second, 1.5ml of pigment is also a suspicious quantity, because you
> don't say how much of this is dry pigment and how much is Photo-Flo.
> I use dry pigments, and the quantity varies wildly with the covering
> power of each pigment. Earths such as burnt sienna, raw umber or such
> cover much less than, say, the quinacridones.
>

Maybe I didn't post this to the list but here is what I wrote on this:
I used 1 to 1 1/2 cm of pigment paste I mix from dry pigment and photo flo
200 (I
didn't measure but I didn't use more then 1.5ml)

> In general, as they say, you should still be able to read newspaper font
> through the coat, albeit with difficulty. This is perhaps not an absolute
> rule but it is good enough for a start. It assures you that the coat
allows
> the passing of light, at least twice. Should you need more density, you
> can always later attempt multiple coats.

No wonder why I get lousy result. but I understand my biggest problem for
the moment could be help in large part with sizing the paper. Of course a
proper layer would help as well.
I can't help myself thinking then why nobody is using a rotary table to coat
the paper. This method allows uniform and thin coating of surfaces just by
controling the RPM.

>
> As an example (not to be taken as words of wisdom written on stone):
> I use some 200mg of Winsor & Newton Indian Red (red iron oxide)
> to cover a 24x30cm sheet of paper sized with two coats of gelatine
> hardened with formaldehyde. I don't use the same paper as you do
> because, as has been previously discussed, it is not available in Europe
> but several members of this list swear by that paper so it must be good.

I guess I'll have to get myself a scale. Formaldehyde, hum! Ain't this stuff
super toxic, I eard the fumes can kill you in the long run. I also see most
of you (gum printers) choose the stuff over anything else. I assume nothing
else comes closes, I saw gloaxial or something sounding like that being used
and what about ALUN or other tanning agent.

I would have concern about using these kind of stuff about the effect they
would have on the permanance of the work????

> Do you size your paper? I don't really recall if this paper is used with
> or without sizing by those that use it.
>
 I know sizing may solve this in part or totally, I'll have to try.

> Photoflo is a good idea when working with dry pigments. I use Agepon,
> the Agfa equivalent, but any surfactant agent should help. Only I use
> it in minimal quantities: just a very small drop which is enough to
> break the superficial tension of the gum+dichromate mix. Perhaps
> you are using too much Photoflo?
>

Yes, It's quite possible I use to much. As I learn more and more of the
inner working of the medium and process. My goal would be to find ways to
minimize if not eliminate the use of additive except maybe for stuff that is
well known ( and documented) to be helpful in the preservation or permanance
of the work.

> I have no experience with the kind of light that you use, so I cannot give
> an opinion. Do you have sunny days where you live? If so, why don't
> try some clear-sky exposure? This is guaranteed to have enough ultraviolet
> content for your needs, mostly between 10am and 3pm or so. But avoid
> the direct sun!
>

The main problem here where I live 45 degre north is that the UV are absorb
my the atmosphere to the point it becomes almost unusable in winter time.

> The uniformity of the coat, within some reasonable range, is not that
> important at first. You will have time to perfect your coating technique
> later, should it be necessary and should you still be hooked with gum :-)
>
> Good luck
> Tom

Thanks a lot Tom, you gave plenty of stuff to think about and try, my best
regards
Yves
Received on Fri Nov 18 11:15:19 2005