So EXA is definitely interesting, and definitely gives lith results on some previously unlithable papers.. However, it has a number of problems that I’m realizing I don’t really want to live with. These problems include:
Must use Glycin. Glycin is only available from one manufacturer, has a terrible shelf-life in powder form, and doesn’t dissolve into TEA particularly well (and doesn’t dissolve at all in most other solvents excluding basic/acidic water where it will quickly oxidize)
EXA still doesn’t produce as deep of blacks on some papers as I’d like and black levels highly depend on sulfite and HQ content. Some of this I’m starting to just chalk up to older Ilford RC emulsions are just crap compared to the deep blacks of MGV, but there is definitely more black capability available when comparing lith prints to normal development.
EXA has really terrible tray life for what I want. It can make 2 prints, at most if deep blacks are desired. It continues to give lithy results with decaying blacks after 2 prints. It’s also extremely sensitive to sulfite and thus it’s a careful balancing act of preserving it while also making sure it continues to work
Highlights and midtones still don’t develop as slowly as I’d like (compared to shadows) in EXA. It’s workable, but it definitely limits the ability to control contrast
So, with this in mind. I’m going a new formulation route, enter the EXB developer series. I stumbled on an expired patent that described a rapid access (ie, fast and high temperature) lith developer containing hydroquinone, phenidone, TEA, substantial antifoggant, and a high amount of sulfite. Some of those are kinda similar to EXA. ie, it contains a secondary developing agent, TEA, and substantial antifoggant. I must’ve read the patent 3 or 4 times by now, but I used the ratios of their formula as a starting point. Of course, their formula won’t just work out of the box. It uses an exotic antifoggant that’s available but discontinued and expensive. It uses a lot of TEA.. like, an expensive amount (~100ml per L of working solution).. And right out of the gate with an adapted and heavily diluted version I made, the amount of phenidone used was unworkably high. I had basically just made a terrible PQ continuous tone developer.
However, here’s my current prototpye formula, EXB4:
15ml HQ-TEA 20%
0.2ml propelyne glycol / phenidone 1% (2ml of 0.1%)
50ml sodium sulfite 10%
4ml potassium bromide 10%
60ml benzotriazole 2%
16ml potassium iodide 10% (!)
2L of water
Adjust to Ph ~12 using sodium hydroxide (probably ~50ml of 3%)
Note! Use fresh fixer and double to triple the normal fixing time. If yellow stains around edges come up while drying, return to fixer.
This formula is great with only minor improvements being figured out at this point, like what results it gives with what papers, if deeper blacks or more tray life is possible, etc. Aside from that though it’s a near ideal developer for many purposes:
Gives incredible difference in development rates between shadows and midtones. After the induction period the highlights and midtones won’t move at all unless you leave it in the developer so long that infectious development gets to it
Quite fast, even at room temp. Induction period is about 2 minutes where the entire print comes up at low contrast, shadows first. For 30s-1m nothing seems to happen, then blacks begin to develop black spots and darken, classic infectious development. Depending on sulfite levels and exact subject printed, deepest blacks will be pretty much complete within 1 minute after the blacks start. With more time blacks continue to spread very evenly throughout the print, touching very low shadows, then middle shadows, etc in a very easy to control fashion for snatch point. My total dev time was probably around 5 minutes, at the very end of the session.
Surprisingly cooltone color spectrum. Some papers might show a hint of warmth especially in blacks, but mostly it’s neutral, lilac, a hint of olive, and deep blacks for a spectrum on the 2 papers tried so far (MGV, Ilford Warmtone RC). This would be an ideal developer for those who don’t like the color of lith prints or that want a mostly blank slate for toning purposes, such as if you want true blues rather than purple with gold toner on a normally warmtone paper.
Fairly coarse grain, especially in shadows.
Great tray life, both in terms of time and print capacity. I was constantly making adjustments as I went, but never added more HQ in 1.5 hours of developing, and it was producing good deep infectious blacks right up until I ran out of time and had to neutralize and dump it. I ended up printing probably 5 8x10 and 6 5x7 prints.
Not greatly sensitive to sulfite content. Despite using a somewhat high amount of sulfite, it did not impact infectious development too much here. It definitely will slow it down some, but it will not harm the depth of blacks and not slow it down exponentially. The difference in my testing between 40ml and 50ml is ~1m of extra development time needed to get blacks to an identical level.
Ilford Warmtone RC in EXB5 (similar to EXB4 but with half the phenidone) with proper fixing
And now time for everyone’s favorite part, my best guesses and experiments on what each component does and how it can be adjusted.
Component considerations
HQ-TEA — I think this actually could’ve been reduced significantly though at the expense of effective tray life. But I haven’t really bothered to test that theory yet.
Phenidone — I chose this based on the patent, but also because it’s a “poor” developer, typically incapable of developing good blacks on its own like other developing agents, ie, metol. The reaction between Phenidone and HQ also is somewhat researched and published. Basically HQ will oxidize in the presence of oxidized phenidone (ie, when phenidone develops a grain) to produce phenidone and oxidized HQ. This oxidation happens stuck to the grain level, and so I guess in a super tiny amount, this basically helps the HQ work evenly across the print and to not carry so much sensitivity to sulfite, since it’s not the HQ causing the HQ to oxidize, but rather the side reaction of phenidone which seems to be responsible for the quick induction period. Note that due to this being a phenidone developer though, the expected decay behavior (aside from lack of buffer capacity) is for the developer to work great until it completely and utterly dies. This is actually kinda desirable for lith printing though, better than a slow inconsistent death where I stand over a tray for 15 minutes cause very little is happening and end up with crap blacks at 25 minutes. Additional phenidone can increase black levels and overall contrast, but too much suffers from runaway development in the highlights and midtones. I recommend making a 0.1% or even 0.01% solution for easy and precise measurement, an almost homeopathic amount of phenidone should be used. No phenidone at all will not exhibit infectious development.
Sulfite — I used a lot cause I wanted to cure the tray life problem. 50ml is definitely plenty for my purposes, but I’d expect you can actually use maybe up to 100ml with still good results. I think at some point the sulfite would eventually hamper the infectious development, but it’s not something I noticed a big difference in by adding more sulfite as I went.
Bromide — Unlike EXA, EXB is significantly less sensitive to bromide. Too much bromide can still decay blacks, but just adding a little bromide will give warmer (olive) blacks. Bromide also functions in a way similar to iodide in regards to tonal separation. Adding bromide will increase the shadow/black separation point so that it can be more easily controlled by snatch point. Basically it will increase contrast levels between shadows and blacks.
Benzotriazole — Some is required to prevent fog either way, but I think there might be too much at this point. Benzotriazole effectively will increase contrast levels between midtones and highlights. At current levels this means that whites tend to clip to actual white, rather than the typical tinted white that comes with normal lith printing.
Iodide — I added this on a whim initially. I couldn’t get benzotriazole to slow down the phenidone enough so that highlights developed slow enough for my liking. This is a greatly effective restrainer that works only on midtones and highlights. A little will restrain the highlights, quite a bit more also restrains midtones. A quite substantial amount will restrain upper shadows as well. I’ve yet to reach an experimental point where it prevented or restrained black development. Basically more iodide means more separation between blacks and the rest of the image. It also will impart a cooler tone. Because silver iodide is significantly less soluble in fixer than silver bromide or silver chloride though, a significantly longer fixing time should be used.
Sodium hydroxide / high pH. I’m not completely sure the pH actually needs to be this high, it’s definitely quite high for a standard lith printing solution. However, I noticed that higher pH actually seems to surprisingly slow down highlight speed to some extent and significantly increases shadow development speed. Of course, a high pH does make the developer less stable, but this can be remedied with the high amount of sulfite. Note that both benzotriazole and iodide will decrease the pH of the developer and so additions should be accompanied by a small addition of alkali