I checked the last 20x16 batch i bought, that was 5207 too. From my undestanding CoT 320 is made by Arches, Bergger than market it.
I find Cot 320 very similar to Platine, (the later being less off white) so with the bad batches of Platine flying around it would not surprise me if some of the latest Cot 320 batches might be effected.
I've a strong felling that you're absolutely right. I suspected that they don't produce any products at all, they simply rebrand them. A.Platine and COT320 are very similar indeed and the eventual differences you can find must be caused by different batches origins.
Arches Platine: Why we didn't carry this paper until this point, I'll never know. Wonderful cool/natural colored paper that is the half brother of Bergger COT-320, since it is made on the same machine, in the same factory, to very similar specs. I find that the surface resists the coating solution a little more than the COT-320, which gives me more time to spread it evenly.
In 2008, Dana Sullivan (from Bostick & Sullivan) (there was a url link here which no longer exists):
The main difference seems to be the absence of a watermark on the COT-320.Maybe also a slight difference of sizing.
In 2008, Dana Sullivan (from Bostick & Sullivan) (there was a url link here which no longer exists):
The main difference seems to be the absence of a watermark on the COT-320.Maybe also a slight difference of sizing.
Manuel,
I look forward the next version of Arches Platine. Any news?
Have just today had some clearing problems with cot 320. What are you guys clearing this paper with? At the moment my clearing method has been.
5 mins citric acid
5 mins EDTA-Disodium
15 mins Hypo Clearing Agent
15 mins EDTA Tetra
It has been working fine for the last couple of weeks however the last few prints have not cleared properly. I have attached a cut sample of what is left after the clearing cycle above. This area was covered with rubylith tape and should obviously be clear. Am going to try a new developer and ferric oxalate to see if that is the problem tommorow. Any other ideas?
David,
I'm only using HCA with great success.
Periodically I make a clearing test, similar to yours, blocking to UV light a small area of the emulsion.
Curiously I never had any clearing problems with this or other papers.
Do you add Oxalic Acid to the Ferric Oxalate sensitizer ? If not, one of the possible answers can be there.
Have just today had some clearing problems with cot 320. What are you guys clearing this paper with? At the moment my clearing method has been.
5 mins citric acid
5 mins EDTA-Disodium
15 mins Hypo Clearing Agent
15 mins EDTA Tetra
It has been working fine for the last couple of weeks however the last few prints have not cleared properly. I have attached a cut sample of what is left after the clearing cycle above. This area was covered with rubylith tape and should obviously be clear. Am going to try a new developer and ferric oxalate to see if that is the problem tommorow. Any other ideas?
Hi Manuel
I get the powder bottles of Ferric oxalate from B&S which i am sure have a small amount of oxalic acid in. How much OA are you adding to a 25ml bottle of FO?
I will try 3 baths of HCA tommorow to see if that helps. The water that comes out of my taps is quite alkaline so it seems to need more clearing other people. The majority of the prints i make have rubylith around the negative to create a clean border, so there is no getting away with uncleared prints!
Hi again David,
Im order the metals and FO in powder from B&S and I always add OA to the sensitizer as follows:
-100ml H20
-27 grs FO
-2grs OA
I don't suppose B&S add OA to the ready made solution of sensitizer.
Other way of helping the ferric oxalate go into solution is to add EDTA Tetrasodium.
This, and to give full development will for sure help to solve your clearing problem.
What developer are you using ? Plain PO solution ? Do you check the developer PH regularly?
I'm a bit confused in reading the last posts, it seems as though you expect potassium oxalate to be acidic, but I've just mixed up a fresh batch of plain po and I'm getting a pH of about 7.2. I've never seen any recipes that call for acidifiying po, or adding oxalic acid to po. I do remember an old thread on replenishment that indicated that the developer should be kept acidic at about pH 6. Are there any references to this in any literature or is this a recent trend?
Do you replenish? Replace? How often? (I've seen many references that indicate that po lasts "forever", it doesn't seem to last very long in my experience with pt/pd.)
Sorry for all the questions, just trying to do the right thing...
Thanks,
Denny
I'm a bit confused in reading the last posts, it seems as though you expect potassium oxalate to be acidic, but I've just mixed up a fresh batch of plain po and I'm getting a pH of about 7.2. I've never seen any recipes that call for acidifiying po, or adding oxalic acid to po. I do remember an old thread on replenishment that indicated that the developer should be kept acidic at about pH 6. Are there any references to this in any literature or is this a recent trend?
Not sure why but I've always had better luck with citric acid than oxalic for pretreating Arches. The 90# is nice for POP platinum and kallitypes. Doesn't seem to really need the prebath for kallitypes, but ziatypes are pretty weak without it. Not sure about DOP platinum.
The paper does seem to have a very slight red bias though, not as neutral as BFK or FAEW, even the 140lb bright white Arches. I've wondered if that tint has something to do with the citric acid. If you have any luck with oxalic and this paper I'll be very interested in it.
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