double-coating pt/pd

[jeffreyg]

Everyone has their own recipe for emulsions. I for one haven't tried double coating but I have found the Bergger COT320 to be more iffy to work with. The Arches Platine is more compatible with my technique. For what it is worth I find 0.5cc of emulsion is enough for a 4x5 and 1.3cc for an 8x10. I use pipettes - accurate to 0.1 ml to measure each solution and a syringe to spread the emulsion to a puddle pusher. For some negatives I might alter the emulsion but that's usually for contrast control. I prefer pt/pd with a tiny amount of gold chloride over single elements but to each his own.

http://jeffreyglasser.com/

[TheFlyingCamera]

Did you take a density reading of the double coated print? We have been discussing related issues over at the hybrid forum at length, here : http://www.hybridphoto.com/forums/showthread.php?t=2047

I will be testing Penn's method of double coating on sheets of paper bonded to aluminium in the next couple of weeks to see if their is a significant difference using a platinum/palladium mix.

I don't have a densitometer at home with which to take readings, so I'm just going by eyeball.

[TheFlyingCamera]

COT320 isn't a good paper for pure platinum prints. The gelatin sizing binds to the potassium chloroplatinite and hinders the chain of reactions which forms the image. Try printing on the reverse side where there's no gelatin. As far as I'm aware there's only one paper which works for a pure platinum image 'out of the box' and that's Buxton.

What would I have to do to other papers to make them ready? Oxalic Acid pre-bath? or something else?

[Ian Leake]

What would I have to do to other papers to make them ready? Oxalic Acid pre-bath? or something else?

The honest answer is that I don't know for certain what pre-treatment is required for other papers. I only use Buxton for pure Pt.

I believe that acid treatment is the secret. I've heard that the first Pt coat may be sufficient to acidity the paper for the second coat. But I've not actually tested this.

[donbga]

As far as I'm aware there's only one paper which works for a pure platinum image 'out of the box' and that's Buxton.

Not so by my experience, Platine worked fine.

[donbga]

From your description this sounds like how the early platinotype printers used to control contrast.

Yes you are correct that was a technique used to control different contrasts in a print.

[donbga]

I don't have a densitometer at home with which to take readings, so I'm just going by eyeball.

If you have a flat bed scanner and the pro copy of Vuescan that supports the scanner you can use that combination to read reflection densities. I would be surprised if you have DMAX readings much above log 1.4 to 1.5. But I think it's sort of foolish to get into this numbers debate, if your "blacks" look black enough then that's all that really matters.

[Ian Leake]

Not so by my experience, Platine worked fine.

Interesting. I only managed to get gritty, dirty, partial images. We must be doing something different (or maybe my paper was dodgy). I may try Platine again. Thanks.

[TheFlyingCamera]

Interesting. I only managed to get gritty, dirty, partial images. We must be doing something different (or maybe my paper was dodgy). I may try Platine again. Thanks.

I'm going to start with Platine as an alternate paper first - in the US, Buxton is ungodly expensive - I can buy a 30x44 inch sheet of Platine for half of what a sheet of 22x30 Buxton costs. Which, if you really want to use it, can be bought from Talas Online.

[jeffreyg]

I don't pretreat Platine. Once Bostick and Sullivan stopped carrying Crane's Platinotype I tried a number of papers but have worked best with Platine. It has a nice natural color, coats easily and has good wet strength. I found that when using a puddle pusher it is best to have a piece of matte board under the paper rather than having the paper directly on a hard surface. I also let the emulsion soak in for about five minutes before drying it.