Development times with FD-72

[Tumbles]

I'm considering using FD-72 fogging developer for reversal processing:

Part - A
EASTMAN Sodium Dithionite: 5.0 grams

Part - B
Water: 900 ml
KODAK 'Kodalk' Balanced Alkali or sodium metaborate tetrahydrate: 10.0 grams
EASTMAN L-(+)Cysteine Hydrochloride: 0.3 gram
Add water to make 1 litre

Use: Dissolve 5 grams of Part A in 1 litre of Part B just before use - it only has a life of about 2 hours after mixing. Otherwise, use as FD-70a.

I was wondering if anyone has a rough idea what the development times might be? Since it's reversal, I could just leave it in until it's finished, but I just want to get an idea of the minimum time. If possible, I hope I could do it for a shorter time, since the rest of the process is such a pain.

Another thing is how difficult is it to handle sodium dithionite? The msds sounds intimidating. It can heat up and possibly catch fire with exposure to air and moisture. It can cause skin irritation and possibly burns. This sounds like something I wouldn't want to deal with.

 

[Raghu Kuvempunagar]

You might want to shoot a strip of 6 frames of the same scene with the same exposure settings. After developing & bleaching them together, cut the strip into individual frames. Redevelop first frame in FD-72 for 1, second for 2, third for 4, fourth for 8, fifth for 16, and sixth for 32 minutes. Compare the results and based on your subjective evaluation, fine tune the time further.

For Kodak's reversal movie film, the recommended redevelopment time was 8 minutes iirc.

Wear gloves.

 

[Tumbles]

Well, I can't use this developer. I called up the local science shop, and they couldn't find sodium dithionite anywhere. Even Sigma-Aldrich didn't have it. Then they saw it was on the can not ship to California list.

Super Iron Out it is, if they even sell it here.

 

[Raghu Kuvempunagar]

Dithionite is also known as Sodium Hydrosulphite.

https://www.dharmatrading.com/chemicals/jacquard_sodium_hydrosulfite.html

 

[Tumbles]

Thanks for the link. I looked up Sodium Hydrosulphite but I completely missed the information that it's used in dyeing.