Nova Monochrome
From Silvergrain Research
Contents |
The product
Nova Darkroom Equipment Ltd. sells a family of slot print processors, one of which is Monochrome model designed for b&w work. These slot processors are arrays of "vertical trays" that save space in darkroom. Monochrome model is designed for room temperature processing, without a heating element seen in color models. Monochrome model is available in 8x10 and 12x16 inch sizes.
The benefit is very clear. It saves space in darkroom. The processing solutions are kept in each slot, and they can be used for a long time with suitable replenishment schedule. Therefore, preparation and cleanup time of printing sessions can be shortened. With reduced air-chemical contact, chemicals tend to last longer, and give off less odor.
Shown on the right above is the 12x16 Monochrome model in my old darkroom setting. Each slot holds 2.0 liter of chemical, and the supplied lid covers (the red piece on left, not shown on right) three slots altogether, although the lid is not air tight.
The slot processor itself is rather well designed and built. The inner walls of slots are textured to reduce adhesion of wet prints to the surface. The print clip holds the print with two sharp pins, which work very well with RC papers, and reasonably ok with fiber based papers. The clip does leave a slightly visible trace near one edge of the print, but unless you use borderless easel, this should not be a problem at all. The slot processor comes with only one clip -- although clips need only a very brief rinse and shake before used again (no need to dry), a few extra clips are almost essential when you print multiple prints, especially of smaller size. (12x16 model can hold 2 8x10 prints in one slot at a time. If you had 4 clips, you could fix two prints while developing 2 other prints, simultaneously.)
The drain valves are located halfway up on the side. When solution is drained from these valves, about 600 ml of solution is still remained in the slot. This is inconvenient, but perhaps there was no other design option because the slot tapers down to the bottom to minimize the amount of solution necessary to filt each slot.
Manufacturer warns not to drain one slot completely while other slots are filled, or to fill one slot completely while other slots are empty. This is probably because the processor is not structurally strong enough. Indeed, one slot takes more than nominal amount of solution to fill up if other slots are empty -- the slot widens due to the solution's weight. This is an inconvenience, but not a serious problem in practice.
Occasionally, prints slip off the clip during processing. This is most likely with fiber based papers (for which a more cumbersome model is sold by Nova, but baryta papers can be processed in Monochrome with care). Prints can be dragged out by using a tongue, preferrably the one that breaks to two halves. Drag prints slowly along the textured wall on the print's back side to avoid potential scratch.
Texture imprinting problem
Since I started recommending Nova Monochrome to photographer friends and also on the Internet, I occasionally received questions about textured print problem. Those prints show imprinted texture from the slot wall in dark areas. Depending on agitation method, this may appear as streaks. Once this happens, the only way to avoid it is to place the print in the developing slot by sliding on its back side, and keep agitating continually for the entire development time.
This texture imprinting problem never happens with absolutely fresh chemical after the processor is thoroughly cleaned, no matter how lousy the agitation is (you may get insufficient or uneven development but this is a different problem). However, when texture imprinting problem is seen, it does not mean that the solution has gone bad. Indeed, if I take the solution to a tray, the prints can be processed perfectly fine. What's interesting is that, when this solution is poured back to the slot processor, it often take away the texture imprinting problem, at least temporarily. This phenomenon is observed with several different formulations of print developers, and it is not likely related to chemical compositions of the bath.
This problem is most likely caused by deposition of insoluble developer reaction products on the inner surface of the developer slot. If the print's front surface touches the inner wall, the deposited developer oxidation products are imprinted on the print surface, and this inhibits the development reaction in situ, resulting in the lighter pattern of the honeycomb texture in the dark areas of the print.
In fact, a thin bottle brush with long handle can be used to scrub off these insoluble deposition off the walls while the developer solution is kept in the slot, or partially transferred to another container. The fuzzy solid pieces of junk will be suspended in the solution until they settle at the bottom of the slot. However, because this development inhibiting compounds are not pushed against the print surface by the slot wall, they present no inhibitory effect, and prints are developed perfectly well, as long as the developing solution is otherwise alive. If the developer is used by replenishement for months and these fuzzy junk increase, they can be filtered out using a laboratory filter paper, or a high quality coffee filter called Chemex.
Incidentally, this honeycomb texture imprinting is more visible when the prints are toned. This is yet another reason why toning is recommended, as a way to increase the print permanence, a way to detect insufficient fixing problem, and this unplesant texture problem.
Wish list
Based on a few years of my own experience, I recommend Nova Monochrome processor in addition to trays. Because you still need to rinse and apply wash aid solution to the prints, you cannot completely remove trays from darkroom. However, 12x16 slot processor replaces 3 12x16 trays in the darkroom sink, which is a quite useful space saving.
As I described above, the Nova Monochrome has a couple of weakness. But most of them can be completely resolved if Nova (1) sold the Monochrome 12x16 model with 4 clips by standard; (2) provided with one floating lid in addition to cover-all lid; (3) did more thorough research on the "texture imprinting problem" and sold the slot processors with a long, thin bottle brush to be used in the way described above.1
Recommended Chemicals
Virtually any standard print developer, stop bath, and fixing bath can be used with this product. However, here are some technical considerations when selecting chemicals.
Exchanging solution is cumbersome with Nova. Therefore, solutions that are long lived with large processing capacity are desirable. Developer, in particular, should be of replenishable type for best consistency.
Print Developer
Print developers are rarely sold with replenisher. Standard Kodak D-72 or Ilford Bromophen type print developers are replenishable with the developer itself, but the best result is obtained if bromide is left out from the replenisher.
My stand-by print developer is DS-14, a neutral tone print developer.
DS-14
Dimezone S 0.2g
ascorbic acid 6.0g
sodium sulfite, anhydrous 12g
potassium bromide 1.0g
triethanolamine, 99% 5ml
salicylic acid 0.5g
sodium carbonate, monohydrate 30g
water to make 1.0 liter
target pH 10.40 ± 0.2
One batch of this solution is made to fill the slot as the developer, and another batch is made without potassium bromide, and use it as the replenisher. The solution keeps in the slot for a few months, but the solution will keep longer if used and replenished regularly.
Stop bath
Since slot processor gives off less odor compared to tray processing, acetic acid stop bath is well tolerable. However, typical dilute stop bath such as 1.7% acetic acid (Kodak SB-1) has small processing capacity, requiring frequent change of the bath. A commercial product such as Sprint stop bath is much superior in this regard. When the Sprint stop bath starts changing the color, you can replenish the stop bath with glacial acetic acid (be very careful not to spill it into the developer slot).
For those who prefer to mix from scratch, here are two buffered stop baths:
Buffered acetic acid stop bath 1
acetic acid, 90% 20ml
sodium acetate 80g
water to make 1.0 liter
target pH 5.05 ± 0.25
Buffered acetic acid stop bath 2
acetic acid, 90% 60ml
sodium hydroxide 25g
water to make 1.0 liter
target pH 5.10 ± 0.25
Either one of these buffered stop baths has much greater processing capacity than dilute plain acetic acid, and does not cause pinhole problems with carbonate developers when used for films. The bath may be replenished at a rate of 30ml glacial acetic acid per 30 sheets of 8x10 or 15 sheets of 11x14 prints processed.
Fixer
Fixer is probably the most problematic, because there is no simple replenishing strategy that does not require a rejuvenating device.
Rapid fixers have greater processing capacity compared to standard fixers. Therefore, I recommend to use a non-hardening rapid fixer at film strength and discard when a hypo test solution indicates exhaustion, or when manufacturer's recommended capacity is reached.
Notes
1 When I communicated with Steve Price, Group Operations Manager and a technical support of Nova Darkroom about this "texture imprinting problem" and my description of how I solve the problem, he maintained that there was no such problem, and the problems I saw were agitation-related problem. My rationale of why this is not the case is explained in the text.(back)
