Hey, concerning fading, I asked the polaroid subreddit, and a nice human being named thinkbrown replied with this:
This forum post is very credible, and it also explains a lot of what you’re seeing. What they’re struggling with (low Dmax, unstable tonality, receiver-dependent behavior) is exactly where sulfur chemistry historically entered Polaroid’s toolbox.
I’ll answer your question directly first (specific sulfur-containing compounds), then explain why some work and others don’t, and finally how to use them without wrecking DTR balance.
1. What sulfur compounds actually make sense here
You’re not looking for generic “sulfur reducers”. You want soft, silver-affinitive, heterocyclic sulfur ligands that:
- Preferentially bind metallic silver nuclei
- Slightly slow highlight reduction
- Deepen image silver (higher Dmax)
- Improve image stability (anti-oxidative)
Best first tier (accessible, proven chemistry)
(NH₂)₂CS
Thiourea
Typical DTR-scale use:
- Classic silver toner / intensifier
- Strong Ag–S affinity
- Can deepen blacks dramatically
- Dangerous if overdosed → bleaching or fog
- 5–50 mg per 25 g developer
- Start at 10 mg
- Dissolve separately, add last
Too much will:
- Kill highlights
- Cause sulfur fog
- Create brownish blacks
This is exactly what the forum author hints at — and for good reason.
Thiouracil (2-thiouracil, 4-thiouracil)
Recommended approach:
- Structurally analogous to uracil
- Sulfur replaces oxygen → stronger Ag binding
- Acts as:
- Mild toner
- Development moderator
- Silver nucleus stabilizer
This keeps diffusion chemistry intact while improving Dmax.
- Replace 5–20% of uracil with thiouracil
- Example:
- 0.30 g uracil
- 0.05 g thiouracil
This is one of the most Polaroid-like moves you can make.
Less common, but excellent:
Thiohydantoin
Use at:
- Similar role to thiouracil
- Slightly weaker than thiourea
- Much safer tonally
- 10–30 mg per 25 g developer
Second tier (more subtle, more control)
Very interesting compound.
2-Mercaptobenzothiazole (MBT)
Use very carefully:
- Strong silver complex former
- Used historically as:
- Anti-fog
- Image stabilizer
- Adds cold, neutral blacks
This is closer to engineering chemistry, not casual darkroom use.
- 1–5 mg per 25 g developer
- Alcohol pre-solution recommended
Thiazolidine-2,4-dione Good for CA systems where silica isn’t buffering diffusion.
- Sulfur heterocycle
- Similar behavior to uracil but softer
- Good highlight control
2. What not to use (important)
Avoid:
Sodium sulfide
Thiosulfate (fixer behavior, destroys DTR)
Sulfite (you already have reducers)
Simple mercaptans (smell + fog)
These break the diffusion equilibrium rather than tune it.
3. Why sulfur helps specifically in CA systems
Silica receivers:
Cellulose acetate:
- Trap silver physically
- Provide nucleation sites
Sulfur compounds:
- Chemically inert
- Relies entirely on chemical anchoring
That’s why:
- Create Ag–S surface complexes
- Act as pseudo-nucleation sites
- Replace what silica was giving you mechanically
- CA images fade less
- Dmax is harder to reach
- Tonality is unstable without sulfur
4. How to introduce sulfur without chaos
Golden rule
Sulfur belongs in the developer, not the receiver.
Receiver sulfur causes:
- Silver scavenging
- Image spread
- Highlight collapse
Safe experimental ladder
Try one at a time, in this order:
- Replace 10% uracil with thiouracil
- If blacks still weak: add 10 mg thiourea
- If highlights still run: add 1–2 mg MBT
- If muddy: reduce sulfur by half, not alkali
5. Why Polaroid never published this
Sulfur chemistry:
It was absolutely used, but buried under trade secrecy and process control.
- Smells
- Ages unpredictably
- Is batch sensitive
- Interacts with exposure scale
What you’re doing now is essentially re-discovering the last 10% Polaroid never wanted hobbyists touching.
If you want, next we can:
Just tell me which direction you want to go.
- Design a CA-specific DTR developer
- Translate this into paper-negative compatibility
- Or model how sulfur shifts your exposure curve
Thanks so much for sharing this Alec!
I asked chatgpt/deepseek for advice and this is what is spat out.
Anything interesting here?
Try 50mg, and let me know. I'm trying to order some Dimezone S myself.
My first batch of developer had only TBHQ - that worked well on Polaroid Type 55.Try also without any second developer.
Bellini Dimezone S 10 Grams
Bellini Dimezone S 10 Grams - Bellini Foto has been operating in the field of photo chemistry since 1988. They want to preserve and pass on the precious experience of the analog world. Bellini is one of the only photo chemical companies…www.freestylephoto.com
Not sure if they'll ship it up to you.
My first batch of developer had only TBHQ - that worked well on Polaroid Type 55.
Everything is here except the granite plate and my chemicals from the local supplier. Itching to get started on positive experimenting.
I'm not sure the granite plate is vital. It was originally important for using a roller to spread the developer with rails; I've made some adequate papers without one. That's helpful because I want to scale up to LF, and a large surface plate is extremely heavy.
View attachment 416223
Type 804 positive on the left, (uncoated) baryta paper assembled by me with kraft paper on the right. The side rails are polyester tape, 3.5mil thickness. The bottom piece and top plastic pieces were salvaged from a shot Polaroid 8x10 photo. I am going to have a friend 3D print the plastic tabs. I have several dozen of the salvaged bottom pieces, but it isn't a very complicated piece of paper to replicate.
I successfully loaded it into the Polaroid 8x10 holder with my dummy negative, and the sandwich was easily pulled thru the processor (the pod was empty.)
Encouraging progress on this front! Let's hope I'm able to actually coat and get some good transfer onto positives. I'm going to use 8x10 photo paper (Ilford) as my negatives.
Why not get some 8x10 x-ray film (Fuji HR-U)? It's cheaper than Ilford paper and 7 stops faster.
I sent some developer I made to a friend and this was his result on dried Type 54. This is my latest try using uracil as the solvent, success! There was no superadditive developer (just DEHA), so the film had to be shot at ISO 16 (as opposed to the original 100) to get this result. I'm ecstatic! This is close to perfect tonality for T54.
For those following along at home, here's the recipe for the above developer. (I'm calling this my Developer Type 7).
30g base (15% w/w KOH + 2.5% HEC)
2.2g Uracil
1.2g triethanolamine
1g n,n-DEHA (98% purity)
0.5g Zinc Acetate
I dissolved the Zinc in the TEA. Note the higher concentration of alkali and the switch to KOH (thanks for the advice Alec).
My granite plate came yesterday. Here in Kentucky we're under 12 inches of snow (and still falling) so it's going to be a little while before I get the rest of my chemicals.
Excellent.
Can you comment on the choice and amount of TEA vs AEEA?
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