View Full Version : Thiocarbamide / Thiourea Question

14-Aug-2010, 20:17
Last batch of toned prints I had a few issues with the softened emulsion from the caustic in my thiocarbamide solution.

I use Oriental FB, and was contact printing 5x7 - I had a good amount of fingerprints in the emulsion once dry, and not from the toning process itself (as I was wearing gloves) - but quite a few of the prints have actual fingerprints (visible swirl marks) which could have only occurred from handling the prints in the post fix/wash or post toning wash phase...edges, corners, only visible once dry (glossy paper)

Larger size prints I've never had a problem, but with the smaller prints I realize I need to take more precaution....

But, I've heard of Potassium Alum hardening solutions following the toning - Is this effective? Are there alternate hardening methods that anyone is using with this toner?

Would these marks be more likely pre-toning (oils reacting with the caustic) or post toning (actually from contact with the softer emulsion)....

Thanks in advance,

15-Aug-2010, 04:00
I have toned a gazillion prints in my life, and all I can tell you is cleanliness is next to godliness, but you probably know that already. I have thought about hardening prints after sepia toning, but I have had few problems so I don't think it is worth the extra effort.

One thing I would suggest is to try cleaning off the marks with a good emulsion/film cleaner.

15-Aug-2010, 20:36
I've never had marks like this after thio toning, but I have noticed a grainy feeling to the paper, which is alleviated by a brief soak in a slightly acidic solution, like citric acid or very weak stop bath.

Vlad Soare
16-Aug-2010, 01:11
I've toned prints in thiocarbamide, and despite all warnings I've even handled them with print tongs. I got no marks whatsoever. The dried surface seems to me to be indistinguishable from that of untoned prints.
The secret is to keep the time in the toner as short as possible. I don't think I've ever exceeded five seconds. Maybe ten if you count the time it takes to pick up the print and move it to the wash tray.
If the toner takes longer than a few seconds to work, then you need to mix a fresh batch.

16-Aug-2010, 06:58
Thanks for the replies...

I use a two part Thiocarbamide toner - and it is mixed and diluted prior to the toning session. It is one shot, and discarded - not saved.

Solution A is the Toner - Solution B is only caustic (sodium hydroxide solution)

By the above answers, I am wondering if the toners being used are different than the toner I am using.

Thanks again,

Vlad Soare
16-Aug-2010, 07:19
Yes, that's the usual variable thiourea toner. The first solution is thiourea and the second one is sodium hydroxide. You mix them in various proportions, depending on the tone you want to get.
It's commonly said that the mixed solution should be discarded at the end of the session, but I have saved mine and used it several times, on the course of several weeks, and saw no change in its activity.

The solution is very basic, indeed, that's why the toning time must be as short as possible to avoid the over-swelling of the gelatin.

16-Aug-2010, 07:35
Thanks Vlad...

I'll try shorter times.

The marks I have in this last batch are only in the 'gloss' of the emulsion....time in the toner could very well be the problem, excess softening possibly...

I usually print with borders and handle in this area, but with the contact prints they are printed to the edge - so the handling marks are visible above dense areas at the edges...

Thanks again,

Jim Noel
16-Aug-2010, 08:25
I have used a great many toners over the past 70 years, and never had fingerprints resulting from this stage of processing.

Since you indicate "a good amount of fingerprints in the emulsion when dry", I strongly suspect you are handling dry paper prior to processing with fingers that have been in contact with fixer and not washed sufficiently. Toners would tend to bring these out more when dry than might be the case with untoned prints.

16-Aug-2010, 11:35
Thanks Jim,

I've never encountered this before myself either...

When working with my final prints, I use fresh gloves with each print from box to wash - only handling the prints by the corners post wash, as I move them from wash to tray. Then again fresh gloves from bleach to wash. And once again handle the corners from wash to toner with bare hands. This is the reason I suspect the wash phases...

Because of the 'swirl' marks - I can narrow it down to basically three parts of the process - the third being final wash, squeegee, to screens....

The wash 'time' may actually be the cause, since the prints have been 'wet' over three wash periods (60 minutes first and final, and 20 minutes post bleach) plus developing and toning times...