Re: Sizing paper with gum and dichromate

Ohhhh, you two are talking about using a layer of exposed dichromated gum sans pigment as a size... Got it now.

I have a suspicion that adding pigment to the mix helps minimize the green dichromate staining and somehow allows the metabisufite to clear any green chromium stain. Don't know why this is so but it seems to be my general observation and impression rather than being a hard fact based on targeted testing. I intended to test this recently but decided to wait until my chemist colleague got back to me with the results of his study of the green stuff.

joe

>>> zphoto@montana.net 12/20/05 11:58 AM >>>
My experience exactly, Kees, but am excited to see how you feel it does as a
size ina comparison to gelatin, below. Thanks for testing this--saves me
mucho time.
Chris
----- Original Message -----
From: "Kees Brandenburg" <ctb@zeelandnet.nl>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Tuesday, December 20, 2005 9:31 AM
Subject: Re: Sizing paper with gum and dichromate

Chris,
I just finished some testing on this subject. I coated several sheets
of BFK (because I had some leftovers). I mixed my gum (homemade from
lumps) and dichromate (saturated pot.di) as I allway do in my
pigmented mix. My usual printing time (UV fluorescent) is 4 minutes.
I coated 6 sheets and exposed for 4, 2, 1 minute and 30 and 15 sec
(all through a piece of blank Ultrafine Crystal Clear film). After
that I left the paper 'develop automaticly' in the water for 1 hour
(as I allways do) and dried. The next day I cleared (at least tried
to) the samples in 5% metabisulfite.

Conclusion: all but one sample had the green stain. The 4,2 and 1
minute exposed had a severe stain. The one that stayed white was
exposed for 15 sec. (i.e. 4 stops under normal). The 30 secs sample
was acceptable allthough stained. Than I coated another one and
exposed for 30 seconds and left this one in the water overnight. Next
morning it looked much better than the first 30 sec. sample.

Next step will be coating these 15 and 30 sec samples with my usual
pigmented mix and look how they behave compared to gelatine sized paper.

-kees

On 20-dec-2005, at 17:06, Christina Z. Anderson wrote:

> Good morning,
>
> I'm late on replying to this post but so it goes at Christmas...
>
> My problem with sizing with gum is this: in order to get the layer hard
> enough to be a suitable size, there will be some discoloration with the
> dichromate that stays in and discolors the whites, in my practice. So by
> experience I agree with kees. If I didn't harden to the point of
> discoloration the layer was too soft. I tried clearing with pot metabi
> but that whole procedure seemed like so much more work than just biting
> the bullet and brushing on a hardened gelatin size (e.g. two separate wet
> and dry cycles). Even so, the layer did not prevent staining.
>
> But I would assume somewhere someone out there has luck with this method
> who is perhaps using lighter pigment loads, although my assumption is
> also that since this method, quoted in the books long ago, never caught
> on as primary practice means it just isn't as good as a plain old
> hardened gelatin size. You know what they say about "assume", though...
> Chris
>
> Probably a much short time will be enough then. But maybe
> the break even point of hardening enough before the staining starts
> doesn't even exists.
> kees
>
> Loris Medici wrote:
>> Hi Kees,
>> But you will still omit the density of the pigment that way...
>> Regards,
>> Loris.
>> -----Original Message-----
>> From: Kees Brandenburg [mailto:ctb@zeelandnet.nl] Sent: 15 Aral*k 2005
>> Per*embe 16:26
>> To: alt-photo-process-l@sask.usask.ca
>> Subject: Sizing paper with gum and dichromate, was Re: glut
>>
>>
>> ...But why not standardize things a little bit more and size with gum
>> and expose with your standard printing time through a clear sheet of
>> printing substrate (or film). I'll give that a try this week...
>>
>>
>
>
>
Received on Tue Dec 20 11:52:50 2005