Thiocarbamide and 1-shot usage

[MarkL]

I usually mix 100ml of stock solutions because they can sit for quite some time and I use very small quantities. The activator can form a precipitate over time (even though I mix with distilled water) and I want to be sure it’s at full effectiveness.

I have been redeveloping 8x10 inch prints 1-shot using very small quantities of toning solution. 6ml total of a combination of toner & activator in about 60ml of water fully redevelops at least 1 print. For example, 3ml toner + 3ml activator + 60ml water. With that little solution of course you would use a flat-bottomed tray.

I just noticed that in his toning book, Tim Rudman says to dilute the thiocarbamide solution 1:9 before use, which I have never done, and have not seen written anywhere else. And in the Darkroom Cookbook the formula indicates half strength thiocarbamide stock solution. I use 1:10 weight to volume for stock solutions.

Anyone see any issues with what I’m doing?!

 

[koraks]

In assume this is about sepia toning.

With thiourea sepia toning, the ratio between the thiourea and the activator (typically sodium hydroxide) determines the image tone. It can be set on a continuum from yellow to purple brown tones this way.

I've made a small illustrated guide for this here: https://tinker.koraks.nl/photography/shades-of-brown-controlling-sepia-toning-hue/
It includes the mixing ratios you need to replicate this.