From: Manuel Gomes Teixeira (punctumgt@netvisao.pt)
Date: 04/10/03-02:03:30 AM Z
Eric ,
Thanks for your reply.
If I understood well both the Pot Chlorate added to the FO or in their own
solution quickly looses its original characteristics and contrast control
very fast. So in what way Pot Chlorate as more predictable results than
H2O2 as Kerik said ?
As I said , I've always got better results with H2O2 than with Pot Chlorate.
Manuel Gomes Teixeira
Punctum Studios Ltd
Aveiro
Portugal
EU
> From: Eric Neilsen <e.neilsen@worldnet.att.net>
> Reply-To: alt-photo-process-l@sask.usask.ca
> Date: Wed, 09 Apr 2003 22:44:38 -0500
> To: alt-photo-process-l@sask.usask.ca
> Subject: RE: hp and pot di with pt/pd
>
> Manuel,
>
> Because you have not read all that has been written on this. Ted Rice
> in Santa Fe was the first printer that I knew that did just that. Every
> time you open a bottle of Ferric Oxalate with the Pot Chlorate added to
> it, you can smell the small release of chlorine. The bottle loses its
> ability to adjust contrast upward. You can mix fresh batches of a
> potassium chlorate solution each time you print. The hard part about
> this approach is that it only requires a small amount to have an effect
> that an accurate measurement may prove too difficult for many.
>
>
>
> Eric Neilsen Photography
> 4101 Commerce Street
> Suite 9
> Dallas, TX 75226
> http://e.neilsen.home.att.net
> http://ericneilsenphotography.com
>
>
> -----Original Message-----
> From: Manuel Gomes Teixeira [mailto:punctumgt@netvisao.pt]
> Sent: Wednesday, April 09, 2003 6:40 PM
> To: alt-photo-process-l@sask.usask.ca
> Subject: Re: hp and pot di with pt/pd
>
> Kerik,
>
>
>
> Tomorrow I'm going to order Na2 for the first time from B&S.
> It will be interesting and useful for all of us to hear some more
> details
> of your and others experiences with this method of contrast control
> in
> Pt/Pd printing.
> I suppose that you use NA2 in substitution of K2PtCl4 when printing
> with
> the classic Pt/Pd approach. Is that so ? Or is there any other more
> complex procedures advised ?
>
> Until now I've had better results with H2O2 added to the sensitiser
> solution than with Potassium Chlorate.
>
> My last question for today:
>
> Why in all Pt/Pd literature is never advised to use Potassium Chlorate
> solution added to the sensitiser as H2O2 and instead is added
> previously to
> the Ferric Oxalate solution ? Is there any chemical explanation for
> that ?
>
> Thanks for your time ! :-)
>
>
> Kindest regards from Portugal
>
>
> Manuel Gomes Teixeira
> Punctum Studios
> Aveiro
> Portugal
>
>
>
>> From: Kerik <Kerik@kerik.com>
>> Reply-To: alt-photo-process-l@sask.usask.ca
>> Date: Wed, 09 Apr 2003 11:09:12 -0700
>> To: alt-photo-process-l@sask.usask.ca
>> Subject: Re: hp and pot di with pt/pd
>>
>> Christina,
>>
>> HP in the developer will increase contrast somewhat, as others have
> stated.
>> However, I really don't recommend this approach. The HP is quite
> unstable
>> and the developer contrast character will likely change during the
> course
>> of a single printing session. Enough to drive you nuts and waste time
> and
>> materials.
>>
>> Sodium dichromate is more commonly used as a developer additive rather
> than
>> potassium, although I would think potassium would provide similar
> effects
>> if you balance the quantity of the dichromate relative to sodium. I
> say
>> this because this approach has been standardized (by Phil Davis, I
> believe)
>> based on a drop count of 50% sodium dichromate solution per a given
> volume
>> of potassium oxalate. If you were to use potassium, I believe you
> would
>> have to use more of it since it will only exist in solution at a
>> concentration of about 11%.
>>
>> And finally, if you haven't already, I really recommend experimenting
> with
>> B&S's "Na2" contrast agent which is added to the sensitizer rather
> than the
>> developer. It gives you a much wider range of contrast adjustment than
>> available with the dichromate approach, and it doesn't cause the
>> degredation of print quality associated with the "Ferric Oxalate No.
> 2"
>> approach that causes so many people problems when the are starting
> with
>> this process.
>>
>> Kerik www.Kerik.com
>>
>>> Good morning!
>>> Does anyone use either hydrogen peroxide or potassium dichromate
> added
>>> to the developer or hp added to the sensitizer (the latter not for
>>> palladium)?
>>> Correct me if I am wrong here: added to the developer, dichromate
> will
>>> increase contrast? And hp will decrease contrast? Why does this
> happen?
>>> Chris
>>
>>
>
>
>
>
This archive was generated by hypermail 2.1.5 : 05/01/03-11:59:54 AM Z CST