koraks
27-Jan-2015, 03:57
I'm about to try my hand at alternative silver processes, specifically Van Dyke brown and kallitype. I already have the chemicals for Van Dyke brown, but I'm having some trouble getting ferric oxalate for kallitype. I have two questions, one about each process:
1. Van Dyke brown: last night, I mixed 50ml of a standard solution for Van Dyke brown (9% ammonium iron citrate, 1.5% tartaric acid, 3.8% silver nitrate). I made separate solutions of each part and mixed them in the right proportions. Now, 12 hours after mixing, I notice a small amount of precipitate that settles in a ca. 1mm layer of cloudy stuff on the bottom of the bottle. The solution is of a dark green, slightly greyish color and mostly transparent. The precipitate particles are tiny and in suspension, they give a sort of grainy look to the solution, which remains mostly transparent. Is this likely to go away over the following days, if I agitate the solution periodically? Is it even a problem? Should I filter the solution? Note that there is no sign of silver plating or cloudiness; just a seemingly small amount of precipitate in the form of tiny tiny particles. I mixed the solutions with demineralized water.
2. Kallitype: I currently have some ammonium ferric oxalate on order, but there have been some issues with shipping it. This supplier (and none of the others where I live) carry ferric oxalate (so without the ammonium), I went with ammonium ferric oxalate. The supplier now asks if it's ok to replace it with an alternative that may be easier for them to source. Since ammonium ferric oxalate will bring the problem of silver oxalate precipitate in a kallitype solution (according to Mike Ware and others who have tried this route; see e.g. here: http://www.apug.org/forums/archive/index.php/t-55518.html), I suggested they try to source some ferric oxalate. My question is two-fold:
* If I stick with ammonium ferric oxalate, is there a good way to deal with the precipitate; e.g. by filtering the solution? Or will it invariably result in a reduced amount of silver ions in the remaining solution causing problems with reduced dmax? Or is it possible to keep the precipitate at a manageable level?
* Is there another way of getting both oxalate and iron(III) ions in the final kallitype solution by using a different combination of salts? I have read some methods that might achieve this (e.g. here: http://www.dmuenzberg.de/boskalli.htm), but I suspect I will run into problems with too much oxalate in the mix, which could again result in precipitate of silver oxalate (right...?)
The simple answer of course would be to buy some ferric oxalate from Bostick & Sullivan, but that would be cost prohibitive since I'm on a different continent, so that option would be a last resort.
Any advice would be very welcome!
1. Van Dyke brown: last night, I mixed 50ml of a standard solution for Van Dyke brown (9% ammonium iron citrate, 1.5% tartaric acid, 3.8% silver nitrate). I made separate solutions of each part and mixed them in the right proportions. Now, 12 hours after mixing, I notice a small amount of precipitate that settles in a ca. 1mm layer of cloudy stuff on the bottom of the bottle. The solution is of a dark green, slightly greyish color and mostly transparent. The precipitate particles are tiny and in suspension, they give a sort of grainy look to the solution, which remains mostly transparent. Is this likely to go away over the following days, if I agitate the solution periodically? Is it even a problem? Should I filter the solution? Note that there is no sign of silver plating or cloudiness; just a seemingly small amount of precipitate in the form of tiny tiny particles. I mixed the solutions with demineralized water.
2. Kallitype: I currently have some ammonium ferric oxalate on order, but there have been some issues with shipping it. This supplier (and none of the others where I live) carry ferric oxalate (so without the ammonium), I went with ammonium ferric oxalate. The supplier now asks if it's ok to replace it with an alternative that may be easier for them to source. Since ammonium ferric oxalate will bring the problem of silver oxalate precipitate in a kallitype solution (according to Mike Ware and others who have tried this route; see e.g. here: http://www.apug.org/forums/archive/index.php/t-55518.html), I suggested they try to source some ferric oxalate. My question is two-fold:
* If I stick with ammonium ferric oxalate, is there a good way to deal with the precipitate; e.g. by filtering the solution? Or will it invariably result in a reduced amount of silver ions in the remaining solution causing problems with reduced dmax? Or is it possible to keep the precipitate at a manageable level?
* Is there another way of getting both oxalate and iron(III) ions in the final kallitype solution by using a different combination of salts? I have read some methods that might achieve this (e.g. here: http://www.dmuenzberg.de/boskalli.htm), but I suspect I will run into problems with too much oxalate in the mix, which could again result in precipitate of silver oxalate (right...?)
The simple answer of course would be to buy some ferric oxalate from Bostick & Sullivan, but that would be cost prohibitive since I'm on a different continent, so that option would be a last resort.
Any advice would be very welcome!