fdoe
Hello
I recently bought a Durst RCP 20 developing machine at a bargain price on eBay. Does anyone have any experience with this machine?
In its original state, the paper is immersed in each chemical for about 2 minutes. Which manufacturers’ products, in what dilutions, are suitable for this?
Has anyone modified the machine to a ‘soaking time’ of about 45 seconds? What ratios would apply in that case?
I’d appreciate any information you can provide.
Best regards
Frank
MirkoBoeddecker
Hi Frank,
I assume you’re running RA-4, right?
As you can’t adjust the individual processing times, you’ll need to fine-tune the DEV-to-BX ratio by adjusting the concentration of the chemicals.
The speed depends on the temperature. So at higher temperatures you can run the process faster than at lower ones. If you don’t have a choice of temperature, speed is the only way to stabilise the process; otherwise you could (within limits) adjust both parameters.
You’d need to ensure full development (no more blue-tinged highlights) but not over-development (blackened highlights), and also bleach-fix (BX) for long enough. If the ratios diverge, you would need to resolve this by adjusting the concentration, as mentioned.
In principle, you should be able to calibrate any chemical solution this way.
It’ll certainly take half a day the first time, though ;-)
Best regards,
Mirko
cfb_de
Hi,
Since there’s nothing you can do about the speed with RCP, that leaves the temperature. Pour in the standard concentration, then try out the sheets one by one, working your way up the temperature scale using a negative with known filtration, exposure time and enlargement. Increase the temperature after each sheet.
There’s no need to adjust the concentration for one simple reason: even in industrial production, the tanks are kept at the same temperature. So you can be sure that, provided the development is sufficient, the exposure will be decent too.
As I understand it, Frank wants to run black-and-white film through the machine. That should work at 26–30°C and with PE paper using pretty much any chemistry. Paper Dur or Moersch Eco, for example, have proven to be stable. Or a suitable machine developer, such as Paper Dur MA. I wouldn’t use N113; if it runs off, it leaves tar in the foam rollers.
No acidic stop bath. The rollers don’t like that (it’s particularly nasty at the inlet to the second tank) and the fixer breaks down faster anyway at the higher temperatures in the machine.
Best regards,
Franz
p.s.: Frank’s post also reminded me again of the idea of a machine. It was quite practical back then. For me, though, it won’t be an RCP, more something compact for the 30cm feed width. I’m now actively looking around for one. The baryta line I was offered recently turned out to be too big and too heavy after all: 70cm feed width, non-deflecting transport, baryta dry-to-dry. Weighing 1.8 tonnes, just as big as my kitchen. And a 50-litre capacity per bath as well as a 360V/40A power connection...
fdoe
Hello
Thank you in advance for your replies.
Yes, that’s right – I only want to use the machine for black and white.
Well, I’ve heard quite a lot about the stop bath now. Until now, though, I’d only ever read that citric acid was a problem. A non-acidic stop bath would naturally include acetic acid as well.
So what would you recommend?
Regards
Frank
cfb_de
Hi Frank,
Any recommendations? It’s quite simple: fill the tanks with developer, water and fixer. Top up the developer every now and then (if you have a higher throughput, use a regenerator; otherwise, a fresh batch will do), change the water bath roughly every other time you use it, and check the fixer regularly (you can see sulphur deposits; test its suitability with a fresh piece of film, similar to a Klötze test).
That would be a simple process control. Even simpler is to completely do away with checking and replacing all the tanks when they no longer work. Unfortunately, you only realise the fixer has gone off when it’s already far too late.
The usual arguments against acetic acid apply, plus: it simply evaporates out of the bath. First it smells a bit, then there’s nothing left in it.
Best regards,
Franz
