Re: NA2 For Pt/Pd BLENDS

Bob,

I meant to say the opposite, that is, you get about the same
contrast, speed and color with 100% palladium as with a 1:3 blend of
platinum and palladium. The color is very warm brown in both when
developed in a 25% solution of potassium oxalate at 120F. If you go
all the way to a 1:1 blend of platinum and palladium the color is
just a tad less warm. This is without the addition of any Na2.

With sodium citrate at room temperature, which I have also used with
palladium, the color of both pure palladium and pt/pd blends is much
less warm, and with ammonium citrate at room temperature the color of
pure palladium is almost neutral, just slightly warm.

Conditions of RH and temperature may give different results, but the
above is what I see in my working conditions of about 70F and 55-65%
RH.

Considering all of this it makes sense to use pure palladium, control
contrast with Na2, and get the color you want with choice of
developer.

Sandy King

>DEAR SANDY (et al.)
> Thanks so much for sharing all of your experience on this topic.
> Sandy, I use Sodium Citrate developer at 100 F and have repeatedly
>found definite differences in image color between 100% Pd and 1:3
>Pt/Pd, all other variables being constant.
> What I understand from your last posting is that I will get
>contrast changes with my blend similar to what one gets using Na2 with
>pure Pd. Thanks. This will be a great starting point for testing
>saving me a lot of wandering in the forest.
> Thanks again!
> CHEERS!
> BOB
>
>----- Original Message -----
>From: Sandy King <sanking@clemson.edu>
>Date: Friday, December 5, 2003 6:03 pm
>Subject: Re: NA2 For Pt/Pd BLENDS
>
>> Clay,
>>
>> In looking back through my notes I now realize that I put my mouth
>> ahead of sound analysis. It is now apparent to me from my own data
>> that my method of testing Na2 in Pt/Pd blends used such small
>> quantities that the amount of pure palladium continued to be the
>> dominating factor, so in essence I got the same ES with pure
>> palladium and blends that contained as much as 50% platinum.
>>
>> Fortunately my observations had nothing to do with the essential
>> testing I did, which was to compare the impact of different UV
>> sources on various blends of palladium and platinum, except for
>> the
>> fact that the amount of Na2 used was too small to merit analysis.
>>
>> However, without Na2, or any other contrast controlling agent in
>> the
>> mix, I got virtually the same exposure scale speed, and color from
>> the use of: 1) 100% pure palladium; 2) a 1:3 blend of Pt/Pd; and
>> 3)
>> a 1:1 blend of Pt/Pd. This was with a developer of 25% potassium
>> oxalate, used at 120 F.
>>
>> Which is to say again, I really can't see any reason for putting
>> any
>> platinum in the blend except for the Na2 which is needed for
>> contrast
>> control.
>>
>>
>> Sandy
>>
>>
>>
>>
>> >On Dec 5, 2003, at 2:16 PM, Sandy King wrote:
>> >
>> >>Clay,
>> >>
>> >>That is interesting, but it definitely worked here.
>> >>
>> >>Have you tested this?
>> >
>> >Not personally. I'm just parroting what I read last night. Next
>> time
>> >I do some printing, I'll run an endpoints test and do a test with
>> >pt/pd/FO at 3/3/6 and one with Na2/Pt/Pd/FO at 2/2/2/6 and see
>> what
>> >I get.
>> >
>> >Clay
Received on Sat Dec 6 13:58:51 2003