RA4 chemicals - mix part or full?
I have a Tetenal Colortec RA4 kit of developer and Blix which makes 5L working solution.
I have a Durst Printo which takes 2.5L - should I mix the whole 5L, put 2.5L in the Printo and teh remaining 2.5L in a 5L container, adding the part used 2.5L after the printing session to this?
Or should I just mix 2.5L, keeping the remaining concentrate in the original containers for when the first 2.5L is exhausted and I need to make up another 2.5L?
Also it says use a stop bath - is water acceptable for this as I don't have any specific stop bath at present, apart from monochrome stop bath (Ilfostop) - but I guess this is not compatable in a colour process?
Thanks for any advice.
Tetenal is easy to mix accurately in smaller amount so I would mix only the 2.5L as the concentrate has longer shelf life.
Matt, I also have a Durst Printo which I use for RA4 and B&W printing.
I only have the intro unit and two heated units. Therefore I use developer in the first, followed by Blix in the second. The paper then comes into a tray of water at room temperature. From there the paper is moved to a wash tray in my sink. From there I put the paper through a 12" RC paper dryer.
I have been using Agfa's 5 litre RA4 kits and still have some left as I bought bulk when Agfa went belly up.
I mix 2.5 litres of working solution for both dev & blix.
I do not mix up the full 5 litres of solutions, it starts going off. That said, I do know that the shelf life of mixed RA4 developer is about 3 months before any degradation that we would notice in our setups, starts to occur.
I have used a 2.5 litre bath of RA4 over quite a few sessions that have stretched to about 6 weeks from the initial mix and use day to the final usage of the bath.
One of the easiest ways to know when your colour developer is going off, is when you notice that your blacks are turning to blue blacks. As soon as this happens, drop the bath, it's gone.
The exit rollers in each bath are, squeegee rollers. These rollers pretty much remove 99% of all chemicals, other than what has been absorbed by the emulsion. You will get negligible carry over into your blix. The Bleach Fix bath has almost double the capacity of your developer solution. This means (in my mind anyway) that your Bleach Fix bath will last at least until the developer is exhausted. Which means that you can then just mix up the rest of the kit to have another 2.5 litres of go juice!
You may also notice that the developer bath temperature dial will be at a slightly lower setting than the Blix bath, to get both baths at the same temperature. Not sure why this is so, but a friend has three thermophot baths on his Printo and has the same thing, whereby the third bath has the highest temperature setting to ensure that all three baths are running the same temperature. On mine it's about 2 degrees C higher required to maintain both baths at the same temperature.
Thanks very much for that Mick - really helpful - I will drop the middle Printo module and this will save up on some space too.
How long is it safe to leave chemicals in the Durst when not in use?
I process RA-4 in open trays, not in a print processor, but I've never had problems with mixing just part of a batch of RA-4 chemicals. I don't recall if I've ever used the specific kit you mention, though. I know that one kit I used came in a single bottle for each bath, with contents that settled into two layers. It was necessary to thoroughly shake the contents to mix the two layers before pouring out just part of a bottle.
As to stop bath, I've generally used normal indicator stop (Kodak and Arista -- the same stuff I use for B&W film and B&W paper) with no obvious problems. I've occasionally used diluted vinegar, too, but I don't recall the dilution ratio I used.
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Matt, although the Printo doesn't have much actual surface area exposed to air, which allows developers to oxidise and go off quickly, it still happens.
About 10 years ago I had a large job which required me to print all day for a whole week. On the last day I left the printo overnight to do some personal printing on the Saturday morning. The bath had done about 1/2 of it's possible throughput. In the morning I fired up the bath and set to work, immediately I noticed things weren't too flash. I was getting too much tar coming onto the prints.
A quick check and I noticed that the input rollers on the Dev tank had tarred up for about 60% of the each of the two rollers. This seemed to occur because the intro rollers, which are a hard plastic stuff (I think), tarred up because of the chemicals oxidised as they sat in the air for hours overnight.
A good R/T machine will have a standby mode where it will sit for about 15 minutes then start up for about 2 minutes, then go into standby mode. Apparently this lessens the tarring effect on the rollers. The working word in the last sentence is, "lessens". I know this as I have worked in pro labs where all of the R/T machines had this feature. They all tar up though, some more so, some less so.
Whenever I have finished a session, I drop the baths into glass bottles and stop them up. This takes approximately 6 minutes to do. Washing the roller cages, about 10 minutes, so allow 16 minutes at the end of any printing session.
Give the Blix unit a quick rinse as that's all it needs.
The dev bath though will invariably have some traces, or more than traces of tarring on the intro rollers. I would advise you to remove these there and then. Leaving them until you come back has always seemed to me, they are harder to remove. Turning the roller cage upside down you may also see traces of tar on some rollers, removal is the best thing, these tar traces will eventually come off onto your prints.
Keeping the rollers really clean is the only way these machines work well. If you allow the rollers to get too dirty, then you may as well not use an R/T machine, you'll lose time and money by constantly re-doing stuffed prints.
One last but very important thing.
The exit rollers on all roller cages, are squeegee rollers!
This means they are soft and pliable. They should never be stored together in their working position. When new, your Printo would have come with specific instructions and little plastic D type spacers designed to sit on the outside, but inbetween, each pair of squeegee rollers.
You should notice that these rollers are spring loaded, which allows you to store them apart. If you don't, they stick together and destroy themselves when you pull them apart.
I bought a brand new Thermophot unit for $50 because it had been stored from the factory like that, it was unsellable, therefore it was written off and I picked it up for obviously beer money, from the then Durst rep.
ALL RA-4 developers tar up after being used some, and this tar settles on all the parts of the developer tank and transport. Leaving the developer in the processor speeds up this tarring process. One should always remove the developer from the processor when done, or if you are set up for replenishment, you should use the processor every day. No down time, otherwise the tar will build.
Regarding stop bath for RA-4 processors. Just a mild acetic-acid stop bath such as you would use for RC b/w paper is fine. Don't use anything fancy, such as pomegranite scented stuff!! Just a wee bit of glacial acetic acid in some water. In some machines, you can get staining from carry-over of developer into blix if you do not use a stop bath.
Thanks for that - Mick, your Printo sounds like it has done plently of work!
On the subject of tar - Nova darkroom, here in the UK, sell a product called "tar buster" so this sounds lke a handy detergent to clean the machine periodically and prevent a build up.