Paper developers: Spur Straight Black and Acurol-P

If you're a regular reader, you'll have noticed that the name "Spur" has been appearing with some regularity on this website. It follows the email exchange with the company's Heribert Schain back in March shortly after AG Photographic announced it would be stocking Spur's HCD developer.

I had a few questions about the developer which I sent to Heribert and he agreed to provide some answers which led to this post. With digital ruling the roost nowadays, it can be difficult getting traction on the internet for new photo chemistry so when Heribert suggested that I could test some of Spur's range of products, I readily agreed. Anything that helps publicise traditional photography products - providing they're good of course - can only help my goal of trying win some converts over to film and darkroom work.


So far, I've tested Acurol-N, an accutance film developer, and HRX-3 New, a fine grain developer. Now it's time for some paper developers to take centre stage although this isn't really a test, more like my general impressions.

The chemicals in question are Straight Black and Acurol-P, both pretty standard paper developers. Heribert also sent me some Acurol-W which is an additive that gives a little warmth to some papers when added to the developer.

I've written in a couple of previous posts how difficult it can be showing the subtle differences between film developers. Well, it's even harder showing the differences between print developers so I'm not even going to try! Suffice it to say that either of these developers will do a great job of your prints. Both produce a full range of well-graded tones with nice deep blacks and clean highlights, all delivered with a neutral to very sightly cool looking tone. Is there much more to ask for?

Straight Black (what a great name for a developer) can be diluted anywhere from 1+9 to 1+24 for economy. Acurol-P should be diluted at 1+15. Both developers keep well in their made up solutions provided that you haven't used one of the higher dilutions. I left both in concertina bottles with the air squeezed out for three days and there was no appreciable difference in their performance when Straight Black was diluted at 1+9 and Acurol-P at 1+15. This is a useful - not to say economical - characteristic if you can only manage to do a couple of prints in one session and can't get back into the darkroom for a while. I tried storing Straight Black diluted 1+19 for a few days but it was clearly a little exhausted.

Ilford MGIV FB Acurol-P with Acurol-W additive:
LtoR - +30ml, +15ml, no additive

Ilford MGIV RC Acurol-P with Acurol-W additive:
LtoR - +30ml, +15ml, no additive

Both developers produce an image tone that is quite neutral. I tried the Acurol-W additive with Acurol-P to see what effect it would have but I don't think MGIV in either fibre-based or resin coated is the best paper for this. You can see the results above. The additive does have the effect of shifting the hint of cool tone produced by the developer to a slight warmth. I didn't have any MGIV warm tone fibre-based paper to hand but I think that it would be noticeably warmer in a warm tone developer without any additive than my examples. Some papers, particularly the Fomatone fibre-based ones, respond more readily to toning and similar sorts of treatment and it could well be that the shift in tone with Acurol-P/W would be more pronounced with them.

The most additive I added was 30ml per litre although the instructions say that up to 50ml can be used. If you look at the comparison pics above you'll see that the additive reduces overall print density a little at this quantity. Anything stronger would have caused further reduction, necessitating further test prints - effectively repeating the procedure all over again and by then I'd run out of time. The active ingredient is Potassium Thiocyanate which is a silver halide solvent. I'd imagine that what's happening here is the chemical is reducing the size of the grain in the print emulsion. Smaller grain usually results in a warmer image tone.

I'll maybe look at the additive in greater detail at a later date as it's an interesting area for experimentation. As with all the Spur products I've tried, I can happily recommend Straight Black and Acurol-P. Your biggest problem in the UK will be getting your hands on them. The best bet is Keyphoto who carry a good range of Spur products or the likes of FotoImpex on the continent.


  1. Amazingly, Freestyle in the USA has Spur HRX-3 and their Agfa Copex Developer. But B&H Photo does not stock any Spur products. There are are zero stores that sell photo chemicals within 25 miles of me so I do chemistry purchases online. I wish it were not that way.

  2. Thank you Bruce. This is very interesting. Your right that developing with SPUR ACUROL-W additional tone for ACUROL-P entails a loss of density. It is for this reason that when using ACUROL-W, exposure time for the paper must be slightly prolonged. As a consequence of users experiencing problems with this, we will in the course of the following weeks publish new, more detailed instructions for ACUROL-W dealing with this issue.